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914World.com _ 914World Garage _ Car stalling AGAIN
Posted by: rjames May 9 2020, 08:18 PM
Drove around for 30 minutes in 80+ degree weather. All arterial roads, so several stop lights, etc. No problems until I was almost home. Car stalled when I stopped at a light. RPMs just dropped to zero. Was able to start it again with a little difficulty and had to keep my foot on the gas to keep it from stalling out again. Power seemed ok though the rest of the way home (I think). It stalled once again at a stop light a couple of blocks from home and then again when I pulled in the driveway. I let it sit for 30 seconds, started it again and it idled just fine. Rock solid at 1000 RPMs. Pulled it into the garage where it sits now.
Prior to today the car has been running and idling perfectly since I went through the FI parts last year, which included installing a 123 distributor, new CHT sensor, a newly rebuilt mps (calibrated for correct afr on my engine), new vacuum hoses, NOS throttle body, rebuilt injectors, new fuel pump, valve adjustment and timing.
I haven’t checked the AFR since last year, not sure why it would change though.
It’s a ‘75 so the fuel pump is in the front, so I can rule out vapor lock I think.
Anyone have ideas as to why it would be stalling?
Posted by: timothy_nd28 May 10 2020, 07:04 PM
What was your AFR last year?
Posted by: rjames May 10 2020, 08:04 PM
What was your AFR last year?
Last setting I made note of: 13.5 at partial load, and 12.5 at WOT. Idle at 12.2.
Will check it again this week.
Posted by: BeatNavy May 11 2020, 05:07 AM
Hey Robert,
12.2 seems pretty rich at idle, IMO. I'd shoot for 13 or 14+, although take idle AFR's with a grain of salt -- the volume and speed of the exhaust gasses have much more error built into them at idle than other loads. I'm dealing with that now (apparently).
The symptoms you describe sounds like it's going too rich at idle when warm, although I'm not sure I'd correlate your AFR with that or not. I'd start looking for other symptoms along that line.
Just to confirm: no problem at load, just at idle?
Posted by: rjames May 11 2020, 06:49 AM
Hey Robert,
12.2 seems pretty rich at idle, IMO. I'd shoot for 13 or 14+, although take idle AFR's with a grain of salt -- the volume and speed of the exhaust gasses have much more error built into them at idle than other loads. I'm dealing with that now (apparently).
The symptoms you describe sounds like it's going too rich at idle when warm, although I'm not sure I'd correlate your AFR with that or not. I'd start looking for other symptoms along that line.
Just to confirm: no problem at load, just at idle?
Correct- just at idle, and just the one outing. Idle speed (except for when I couldn’t keep it running) is a solid 1000 rpms.
Hope to look at the afr numbers again tonight.
Posted by: BeatNavy May 11 2020, 06:53 AM
Maybe lean out your ECU knob a few clicks (it has very small impact) and see how that does. If idle becomes unstable, probably have gone too far.
Or there is something else going on...
Posted by: StarBear May 11 2020, 07:40 AM
Presuming it's a 1.8L (75), try the dual relay (under the battery tray) - exactly describes what happened to my 74 1.8L about a year ago. Chased it for 6 months. When in/down there, check the capacitor, too; I had a loose wire that may have contributed to the situation.
Posted by: rjames May 11 2020, 04:21 PM
It's a 2.0 liter. Sorry, should've clarified.
If I change the ECU settings the idle starts to hunt. Really it's been running perfect and for fairly long drives without any issues. No issues detected right before it died when stopping at the light, and then again a few blocks later. Power was fine for the entire 30-45 minute drive, right up until it died. Then power seemed ok I think, but may have been low. Seems odd that it would stall twice in the space of a few minutes, then after sitting 30 seconds fire right up and hold idle just fine (like it did before it stalled).
I haven't taken it out yet, but am a bit afraid to try to take it out to get AFR readings and adjust the MPS for fear that it' will leave me stranded.
Someone suggested looking at the coil. I replaced that last year with a new one. Doesn't mean it couldn't be bad, but how do you test an intermittent coil issue?
Posted by: rjames May 13 2020, 11:58 PM
So I went to see if I could drive it around and measure the AFR and when I started it up cold, the idle stayed at 1000 RPMs for about 10 seconds (which is lower than where the idle should be when cold) and then stalled. After starting it again (it starts quickly) it only lasted a few seconds before stalling. I did have enough time to verify that the AAR is working correctly before pushing it back into the garage.
Hoping it's the coil since i have a known good spare. Will try swapping coils this weekend unless someone has another idea for me to try.
Posted by: dr914@autoatlanta.com May 14 2020, 08:33 AM
if it is a 1.8 the air flow meter flap could be sticking and that would cause your problem. They get hot and the device expands causing the warped flap to stick in the bore, and suddenly the control unit thinks that the car is running at 140 miles and hour and adds all of the extra fuel. As long as you have your foot in it, it is just running rich, but as soon as the car comes down to idle it cannot handle the extra fuel and floods out. THEN the air flow meter cools a bit the flap unsticks, the car starts, and it as if nothing has happened. Check the oil level as well, as this condition causes the extra richness to dilute the oil with gas
Drove around for 30 minutes in 80+ degree weather. All arterial roads, so several stop lights, etc. No problems until I was almost home. Car stalled when I stopped at a light. RPMs just dropped to zero. Was able to start it again with a little difficulty and had to keep my foot on the gas to keep it from stalling out again. Power seemed ok though the rest of the way home (I think). It stalled once again at a stop light a couple of blocks from home and then again when I pulled in the driveway. I let it sit for 30 seconds, started it again and it idled just fine. Rock solid at 1000 RPMs. Pulled it into the garage where it sits now.
Prior to today the car has been running and idling perfectly since I went through the FI parts last year, which included installing a 123 distributor, new CHT sensor, a newly rebuilt mps (calibrated for correct afr on my engine), new vacuum hoses, NOS throttle body, rebuilt injectors, new fuel pump, valve adjustment and timing.
I haven’t checked the AFR since last year, not sure why it would change though.
It’s a ‘75 so the fuel pump is in the front, so I can rule out vapor lock I think.
Anyone have ideas as to why it would be stalling?
Posted by: rhodyguy May 14 2020, 08:56 AM
2.0 Djet. I think a 123 distr.
Posted by: 914_teener May 14 2020, 10:21 AM
My quess is a kinked fuel line underneath the rack cover.
Check your fuel pressure.
Second best quess is there is vacumm leak. Sure you have the ported vacuum line to the 123 set up right?
Posted by: rjames May 14 2020, 10:56 AM
My quess is a kinked fuel line underneath the rack cover.
Check your fuel pressure.
Second best quess is there is vacumm leak. Sure you have the ported vacuum line to the 123 set up right?
Yes- Djet 2.0, 123 distributor.
Doubt a fuel linked itself after several months of not being kinked.
Vacuum leak would cause high idle.
I’m starting to wonder if my new (to me) MPS went bad with a torn diaphragm.... will check to see if it holds vacuum and report back.
Posted by: 914_teener May 14 2020, 11:47 AM
My quess is a kinked fuel line underneath the rack cover.
Check your fuel pressure.
Second best quess is there is vacumm leak. Sure you have the ported vacuum line to the 123 set up right?
Yes- Djet 2.0, 123 distributor.
Doubt a fuel linked itself after several months of not being kinked.
Vacuum leak would cause high idle.
I’m starting to wonder if my new (to me) MPS went bad with a torn diaphragm.... will check to see if it holds vacuum and report back.
MPS yes...that is a symtom of a cracked diaphram..BTDT.
I quess where I was going with the 123 dizzy comment is are you running ported vacuum to the dizzy?
Posted by: rjames May 14 2020, 05:36 PM
My quess is a kinked fuel line underneath the rack cover.
Check your fuel pressure.
Second best quess is there is vacumm leak. Sure you have the ported vacuum line to the 123 set up right?
Yes- Djet 2.0, 123 distributor.
Doubt a fuel linked itself after several months of not being kinked.
Vacuum leak would cause high idle.
I’m starting to wonder if my new (to me) MPS went bad with a torn diaphragm.... will check to see if it holds vacuum and report back.
MPS yes...that is a symtom of a cracked diaphram..BTDT.
I quess where I was going with the 123 dizzy comment is are you running ported vacuum to the dizzy?
No vacuum lines to the dizzy.
Posted by: rjames May 16 2020, 03:13 PM
Ok, tried adjusting the MPS, but can’t keep the car running after it warms up unless I’m on the gas. Revs easily though.
Pulled vacuum on the MPS and it does leak. About 1 inch per 2 minutes. So that’s no good.
To make sure that’s the issue, if I disconnect the vac hose from the MPS the car will also stall.
Should it idle with the hose to the MPS disconnected? (Albeit maybe badly)
Actually, I just realized that if the hose was disconnected from the MPS it would think the car was WOT and flood it with gas which would cause it to stall, right?
I guess I’m rebuilding the MPS to see if that fixes the issue.
Posted by: BeatNavy May 17 2020, 05:25 AM
Actually, I just realized that if the hose was disconnected from the MPS it would think the car was WOT and flood it with gas which would cause it to stall, right?
Yes. Do you have access to a spare MPS for testing? I've got a spare 043 I could loan if you need it. May take me a day or two to send. The alternative is to go ahead and drill this one out and verify a bad diaphragm and get the repair kit from Chris.
Posted by: rjames May 17 2020, 09:51 AM
Actually, I just realized that if the hose was disconnected from the MPS it would think the car was WOT and flood it with gas which would cause it to stall, right?
Yes. Do you have access to a spare MPS for testing? I've got a spare 043 I could loan if you need it. May take me a day or two to send. The alternative is to go ahead and drill this one out and verify a bad diaphragm and get the repair kit from Chris.
That’s a very generous offer, thank you.
The MPS I have was already opened up and I have a spare rebuild kit for it. I bought it as a recalibrated unit from Jeff Bowlsby last year, but it still had the original diaphragm I think. If I can’t get it to seal after rebuilding it I may take you up on your offer.
Posted by: rjames May 17 2020, 04:12 PM
Went to rebuild the MPS.
I opened it up and the diaphragm was fine. Cleaned everything off put it back together and it still didn’t hold vacuum as well as it should. I actually have another MPS that I tried to remove the outer screw on awhile back and totally buggered it up. So just for fun I took the bottom part (where the vac line connects to) of the MPS I was running in the car and replaced it with the bottom of the other MPS I had and cleaned all the seals gasket etc. and put it back together to see if it would hold back in better.
Vacuum held better, a little bit of a leak down but less than 1 inch after five minutes. Installed it an the car stayed running. Got the idle dialed in. Great, fixed!
Went in the house for lunch and came back out an hour later to drive it.
Car wouldn’t stay running again,
Tried swapping the coil with a known good coil- no change.
Then I realized I didn’t hear the fuel pump running. Discovered my relay board was bad. Man, all this work and it’s the fuel pump. How did I miss hearing that it wasn’t running?! Swapped out the bad board for a good one and the pump starts running again and everything was great car idles perfectly. Took it out for a spin and as soon as I drive 1 block and let off the gas the car stalled again. I verified that the pump is running so the bad relay board must’ve just been a fluke in the middle of things.
I’m at a complete loss now. MPS is leaking but just barely. Is it still a suspect?
Posted by: BeatNavy May 17 2020, 04:53 PM
I’m at a complete loss now. MPS is leaking but just barely. Is it still a suspect?
No, leaking an inch every 5 minutes is well within spec, IIRC. Something else is going on. What a mess, eh? It's hard enough troubleshooting one thing much less 2 or more things. Back to fundamental troubleshooting
Posted by: Mark Henry May 17 2020, 08:00 PM
Vacuum leak would cause high idle.
Small leak or worn TB bushings yes, but not if it's a large leak. A large leak would act like the OP's issue.
Are the vacuum hose to plenum in the correct spot? Not the same but when I had my 2.0 with SDS EFI (stock djet intake) I connected the vacuum line into the wrong port and it wouldn't idle worth a crap. I swapped the hose to IIRC the correct djet MPS port and it solved the issue.
Posted by: Rand May 17 2020, 09:52 PM
I was going to ask if you listened for the fuel pump running. Mine was doing the same thing and it was a faulty fuel pump intermittently stopping. If the MPS was the culprit it usually means constant rather than intermittent behavior.
Posted by: rjames May 17 2020, 11:25 PM
Vacuum leak would cause high idle.
Small leak or worn TB bushings yes, but not if it's a large leak. A large leak would act like the OP's issue.
Are the vacuum hose to plenum in the correct spot? Not the same but when I had my 2.0 with SDS EFI (stock djet intake) I connected the vacuum line into the wrong port and it wouldn't idle worth a crap. I swapped the hose to IIRC the correct djet MPS port and it solved the issue.
Car has a NOS throttle body. Hoses are in the right spot. Car was running perfectly for ~9 months. Hadn’t touched anything until it started stalling. I thought I had it fixed twice-once when swapping the MPS parts and again when the fuel pump wasn’t running. After each ‘fix’ the car idled for several minutes without any issues.
Car seems to have plenty of power when I’m on the gas. Instantly dies if I let the RPMs drop below 1600 or so.
Posted by: rjames May 20 2020, 12:09 AM
Well...I’m perplexed.
Started it up and cold, the idle was too low. Decided to start at zero again and took another run at getting the MPS, the TB idle adjustment screw and the ECU knob set correctly. I had started moving the settings of all of these all over the place when trying to get the car running before.
Car is purring again and I was able to drive it a few miles without it stalling. Ran great with plenty of power.
AFR 13.1 at idle. Best I could get. Need to dial in the AFR at WOT still but it’s in the ballpark.
In the end, the only thing I really did was clean and reseal the MPS. I don’t trust it for a long drive yet. Time will tell. I have a hunch that the fuel pump may have an intermittent issue since the supposedly bad relay board I took out when the fuel pump wouldn’t run ended up testing good for continuity.
Posted by: rjames Jun 6 2020, 11:14 AM
It’s back. Was running fine with no issues for several long outings. Then yesterday it started happening again after 20 minutes of driving. Verified the fuel pump is working.
Power seems fine above 2000rpm. If I press in the clutch and let off the gas the RPMs drop to zero and car dies.
When it’s in this state, in neutral the car does not rev smoothly when below 2000rpms and is hard to keep running. If in gear and driving, I can keep the car running without any real issue as long as I’m giving it gas.
Each time after it dies it starts right up no problems, but I do have to keep the rpms up to keep it running.
Something else I noticed was the rpms kind of jumping erratically up 100 rpms while maintaining a constant speed on the freeway. Hadn’t seen that before.
Given everything I’ve already tried to solve this, I’m starting to suspect the 123 distributor. I have the stock distributor I can swap back in but really hate having to go through all that again.
Symptoms don't seem indicative of a bad distributor based on what I've read on the interwebs. Anyone think this could be a distributor issue?
If the compression was bad, that would mean it would be doing this all the time instead of intermittently, right?
Posted by: rjames Jun 10 2020, 12:59 PM
Bumping the thread to break the silence of the crickets.
Posted by: cuddy_k Jun 10 2020, 09:00 PM
I know you changed the relay board, but did you change the relays? I had the same exact symptoms and it ended up being a bad relay. Drove me crazy as I couldn't predict when or where it would cut out.
Posted by: rjames Jun 10 2020, 11:38 PM
I know you changed the relay board, but did you change the relays? I had the same exact symptoms and it ended up being a bad relay. Drove me crazy as I couldn't predict when or where it would cut out.
Thanks- yeah, and I verified the fuel pump is running even when it wants to stall.
Posted by: mepstein Jun 11 2020, 04:21 AM
Fuel filter or tank screen?
Posted by: rjames Jun 11 2020, 06:00 PM
Fuel filter or tank screen?
Replaced the filter last summer and haven’t put many miles in since. I refurbished the tank and replaced the screen several years ago, although I suppose anything’s possible.
When it stalls it seems to run ok if I keep my foot on the gas and the rpms over 2k. Drove back home on the freeway without any issues until I let off the gas. Seems like if it was stalling because of lack of fuel I wouldn’t be able to drive it at all or it would buck/hesitate every now and then.
.
Posted by: bzettner Jun 11 2020, 07:43 PM
I read thru this yesterday but can't remember if you've rechecked the fuel pressure recently?
Posted by: JOEPROPER Jun 12 2020, 06:41 AM
Your critical inputs are your MPS (which You've been thru), CHT, TPS and RPM (distributor). I would go after the RPM next. As long as your fuel pump is still working and fuel delivery is correct and vacuum hoses and routing is correct then as you suspected, the distributor may be at fault. I think you should go that route and see what you find.
Posted by: rjames Jun 12 2020, 10:11 AM
I read thru this yesterday but can't remember if you've rechecked the fuel pressure recently?
I don't have a gauge to test, but it's on the list of things to check. That said, if fuel pressure was an issue, I would expect to see issues when I am at partial load or WOT, and not at idle when fuel pressure is lowest, no?
Posted by: BeatNavy Jun 12 2020, 10:24 AM
I read thru this yesterday but can't remember if you've rechecked the fuel pressure recently?
I don't have a gauge to test, but it's on the list of things to check. That said, if fuel pressure was an issue, I would expect to see issues when I am at partial load or WOT, and not at idle when fuel pressure is lowest, no?
Fuel pressure is constant on stock setup. Most newer fuel pressure regulators do lower pressure at idle based on manifold vacuum, but not our stock unit.
It's worth checking. Unfortunately you've run out of obvious and simple things to check. Now you need to make a list and check it twice...
Posted by: DRPHIL914 Jun 12 2020, 12:51 PM
I read thru this yesterday but can't remember if you've rechecked the fuel pressure recently?
having dealt with similar issue recently well actually a couple times in past few years, similar acting but - one time was the fuel pump, it was slowly going bad, I have a in line fuel pressure gauge now just for that reason, pressure should be constant if you can see if that pressure went down you have an issue with that pump or blocked screen or filter like mark and beatnavy says.
- the next time it was a MPS that was failing electrically - diaphragm not torn, held vac ok, but the MPS not always sending proper signal. I just don't think its your distributor but try the other one anyway. only make a change to one thing at a time. and as prevous person said, recheck everything again. all electrical and grounds. but I really think it may be with fuel supply/pump.
Posted by: rjames Jun 18 2020, 10:18 PM
Ugh. Well today I eliminated the following 3 things from the shrinking list of possible causes for my car stalling:
Fuel pump: I verified pressure is at 29 both when it’s running and when it stalls.
CHT: swapped in a known good one (didn’t bother testing the one I took out)
Distributor: I thought this was the issue- removed the 123distributor and put in my old stock dist. Car stayed running long enough for me to think it was fixed. Verified the timing again, made slight adjustment to dial it in, car still running...got in and drove 6 blocks and it stalled as soon as I took it out of gear. As before, if it stays in gear and the car is moving (even when completely off the gas) it keeps running.
The only other thing I can think of is the old ignition wiring in the engine bay is bad somewhere.
Posted by: 914_teener Jun 19 2020, 12:23 AM
Think about this. A loose connector or bad wire creates more resistance and thus heat when current runs through it.
Check all the primary circuts to the engine. Never read anything about the injector harness, ground points or ecu comnector.
Posted by: rjames Jun 19 2020, 12:33 AM
Think about this. A loose connector or bad wire creates more resistance and thus heat when current runs through it.
Check all the primary circuts to the engine. Never read anything about the injector harness, ground points or ecu comnector.
I have 2 supposedly good ECUs, swapping them out hasn’t fixed the issue.
The wiring in the engine bay is original and old and a prime target for faults. I saved them for last because the cost of replacing the ignition harness and the injection harness is significant, especially in this time of income uncertainty. But unless someone has another idea, I guess that’s what next on the list.
Posted by: BeatNavy Jun 19 2020, 05:05 AM
That sucks, Robert. Sorry about the frustration. Several years ago I splurged and bought a new harness from Bowlsby. It may have prevent a lot of aggravation over the years.
I'm not using it currently. If you want I could possibly loan it out to you for testing purposes. It's got a couple of years of hard use on it, but it's still in good shape.
Posted by: JOEPROPER Jun 19 2020, 09:27 AM
The only other thing I can think of is the old ignition wiring in the engine bay is bad somewhere.
I would look at this carefully.
Posted by: rjames Jun 19 2020, 12:40 PM
That sucks, Robert. Sorry about the frustration. Several years ago I splurged and bought a new harness from Bowlsby. It may have prevent a lot of aggravation over the years.
I'm not using it currently. If you want I could possibly loan it out to you for testing purposes. It's got a couple of years of hard use on it, but it's still in good shape.
Thank you! As always, I really appreciate your generosity. That said, I bit the bullet and will be ordering a new ignition harness from Jeff. Fingers crossed.
Given everything I've thrown at this car in the last few years it may just been cheaper to buy a running 914.
Posted by: BeatNavy Jun 19 2020, 01:22 PM
No problem, Robert. Boy I hope that wiring harness improves things. Definitely check ignition harness while you’re at it.
Good luck! 
Posted by: logica Jul 15 2020, 11:55 PM
I have similar symptoms in my '74 2.0 EFI. This week, I changed all of the vacuum hoses, replaced and relocated the fuel pump to the front of the car (to eliminate the vapor lock issue), installed new fuel lines, and fuel filter, and the problem does not go away. The car is now idling closer to 1100 RPMs versus where I typically have it set up around 1000 RPMs. The problem seems to exacerbate after I run the car wide open in the highway going over 70 MPH for more than 20 minutes.
Posted by: bgconsul Jul 16 2020, 10:42 AM
I have similar symptoms in my '74 2.0 EFI. This week, I changed all of the vacuum hoses, replaced and relocated the fuel pump to the front of the car (to eliminate the vapor lock issue), installed new fuel lines, and fuel filter, and the problem does not go away. The car is now idling closer to 1100 RPMs versus where I typically have it set up around 1000 RPMs. The problem seems to exacerbate after I run the car wide open in the highway going over 70 MPH for more than 20 minutes.
This is too strange, I also have the same problem with 74 2.0 Djet EFI. idle is about 1100, Runs normally after easy start up, intermittent stall problem is identical. AFter driving for 10 minutes, idle falls to zero, stalls out. Need to hold pedal to floor to get to restart. Exhausted all the typical remedies so took it to Porsche shop in Sac. They said the battery was not providing enough amp, replaced battery and idle seemed fixed, no stalls at stop. Now problem is back again. I have read the posts and cant figure it out.
Posted by: rjames Jul 16 2020, 12:13 PM
Since I started this post, I'll give an update on where things are at, and also respond to the other two people who are having similar issues.
Got the new ignition harness from Jeff. A work of art. Installed it yesterday and spent an hour re-tuning the mps. I thought I had it dialed in, but I realized that at idle the AFR was way to rich at ~11.2. Although the part load AFR was good at ~13.5.
Maybe this was part of the cause of the stall all along? Maybe it was a combination of old wiring and an idle that was too rich? Maybe nothing is fixed and it just hasn't stalled yet?
So I'm back to trying to dial in the AFR and the problem I'm running into now (what what I ran into before) is when I set the AFR set for partial load (~13.5) using the MPS inner adjustment screw, the the idle AFR ends up being too rich (~12.5).
So I then try to lean out the idle AFR using the throttle body air bleed screw and the ECU adjustment knob to a point where the idle speed is at 900-1000k and doesn't hunt, but that puts me at 12.7 at best. I see others at 14+ AFR at idle.
What am I doing wrong here?
As far as the others who are having stalling issues... start a new thread.
I say that not to be a jerk, but because there's a lot of potential causes that you are seeing similar symptoms, and going through them all will not only derail my thread but it will make it harder to troubleshoot your particular situation. 
Posted by: second wind Jul 16 2020, 12:38 PM
I have to share my recent experience as I include a couple different aspects but identical symptoms. '73 2.0 all stock with Pertronics 2....I think the smog idle device (afr?) is removed. So after many vapor lock issues moved fuel pump up front and problem disappeared. I drive maybe 3-4,000 miles a year...maybe 5,000. So car has worked perfect and routinely for last couple of years but a month ago started to do the low idle no start when warm routine. I discovered a broken wire on the temp sensor on top of the plenum (temp sensor 1 I believe) and repaired it. I also have a throttle body cleaning machine, BG Products, and did the cleanse as well. After I clean the throttle body I can hear the idle adjustment screw much clearer and usually have to turn the idel down. I think these cars like a really clean throttle body. Car ran like a jet and started perfect so I thought I was out of the woods. I accidently pulled the cold start injector plug out upon re-assembly and car would not start next day and I missed the recent SoCal ride. Anyway cars seems all cured now. Hope that offered something.
All the best to all,
gg
Posted by: rjames Jul 16 2020, 01:05 PM
So I was able to drive around for an hour last night, constantly stopping to adjust the MPS which means there was a fair amount of idling mixed with short drives, engine always running. That equals a very warm engine and there was no stalling.
Just took it on the freeway for 20 minutes, AFR at a steady 13.5 while cruising and as soon as I get off the freeway it of course stalls again. I’m typing this in a parking lot 30 miles from home hoping the car will make the drive back.
I’m almost out of things to try. My car has become a paperweight just in time for summer again.
_____
**Update**
I let it sit for 15 minutes or so and it started right up and idled just fine. Made the trip home and it stayed running when I pulled into the driveway. 
Back to basics: Air, fuel, spark, compression.
Under what conditions for any of the four categories above would allow the car to keep running fine with my foot on the gas with no <apparent> lack of power but stall when off the gas?
Air seems an easy one to take off of the list.
Fuel: Lines are new and good and new filter. Verified that the fuel pressure stays in spec even when the car wants to stall. Bosch fuel pump is mounted in the frunk and has less than 1000 miles on it. Injectors sent out for cleaning and are within spec. New injector seals.
Spark: New ignition harness. Tried both stock and electronic distributor. Tried both stock and new coil. NKG plugs and wires have less than 1000 miles.
Compression: Haven't checked, but car has good power and compression isn't an intermittent thing, right?
All vacuum lines replaced, new plenum hoses, intake gaskets, TB gasket, and NOS TB. Verified no vacuum leaks (including plenum). Tried 2 different MPS (both hold vacuum).
New CHTS, also tried swapping with old one.
Swapped relay boards (connections tested good on both of them).
ECU is next on the list to swap out. (I may have already tried this, but I can't remember).
Posted by: yellowporky Jul 16 2020, 01:47 PM
maybe i missed it but have you tested the electrical connections on the MPS?
You can send your extra ECU to Fuel injection Corp in Tracy california and they will test if for free.
Also triple check your grounds including the trans to body.
On a project car we ran into some fuel line that collapsed after a couple months of sitting full of fuel. Lucky we found it while still working on the car or that would be an area that we would not have thought to check since it was new.
Posted by: rjames Jul 16 2020, 01:52 PM
maybe i missed it but have you tested the electrical connections on the MPS?
You can send your extra ECU to Fuel injection Corp in Tracy california and they will test if for free.
Also triple check your grounds including the trans to body.
On a project car we ran into some fuel line that collapsed after a couple months of sitting full of fuel. Lucky we found it while still working on the car or that would be an area that we would not have thought to check since it was new.
Grounds are good from injection harness and I have a newer trans to car body strap.
New fuel lines
Tried 2 different MPSs
I haven’t tried swapping the ECU yet- I have a spare so that is next.
Posted by: yellowporky Jul 16 2020, 07:55 PM
have you tested either of MPS electronics? Vacuum is only part of the equation
you are going to keep going in circles if you do not start from the very basics and systematically check off everything even the items that you say are new but they are not new since after the problem started.
Those are my thoughts
Posted by: rjames Jul 17 2020, 11:07 AM
have you tested either of MPS electronics? Vacuum is only part of the equation
you are going to keep going in circles if you do not start from the very basics and systematically check off everything even the items that you say are new but they are not new since after the problem started.
Those are my thoughts
Thanks for the suggestion, but as mentioned in at least one previous post, I have tried 2 different MPSs. One of them was good except for a blown diaphragm (which has since been fixed) and the other was re-calibrated to factory specs and is in the car now.
I believe I've done a pretty complete job of documenting all of the things I've tried already- including 'the basics'. It's a lot of reading to go through the whole thread, but I appreciate anyone who is willing to do so to help.
I welcome the input, so if there's something I've missed keep the ideas coming.
Posted by: BeatNavy Jul 17 2020, 02:30 PM
Robert I have a new-ish FI wiring harness and 043 ECU I can loan you for testing. Which ECU do you need?
Posted by: 914_teener Jul 17 2020, 04:52 PM
So I was able to drive around for an hour last night, constantly stopping to adjust the MPS which means there was a fair amount of idling mixed with short drives, engine always running. That equals a very warm engine and there was no stalling.
Just took it on the freeway for 20 minutes, AFR at a steady 13.5 while cruising and as soon as I get off the freeway it of course stalls again. I’m typing this in a parking lot 30 miles from home hoping the car will make the drive back.
I’m almost out of things to try. My car has become a paperweight just in time for summer again.
_____
**Update**
I let it sit for 15 minutes or so and it started right up and idled just fine. Made the trip home and it stayed running when I pulled into the driveway.
Back to basics: Air, fuel, spark, compression.
Under what conditions for any of the four categories above would allow the car to keep running fine with my foot on the gas with no <apparent> lack of power but stall when off the gas?
Air seems an easy one to take off of the list.
Fuel: Lines are new and good and new filter. Verified that the fuel pressure stays in spec even when the car wants to stall. Bosch fuel pump is mounted in the frunk and has less than 1000 miles on it. Injectors sent out for cleaning and are within spec. New injector seals.
Spark: New ignition harness. Tried both stock and electronic distributor. Tried both stock and new coil. NKG plugs and wires have less than 1000 miles.
Compression: Haven't checked, but car has good power and compression isn't an intermittent thing, right?
All vacuum lines replaced, new plenum hoses, intake gaskets, TB gasket, and NOS TB. Verified no vacuum leaks (including plenum). Tried 2 different MPS (both hold vacuum).
New CHTS, also tried swapping with old one.
Swapped relay boards (connections tested good on both of them).
ECU is next on the list to swap out. (I may have already tried this, but I can't remember).
So once at band camp..........
Electrical connector primary circuit somewhere....maybe even at the.fuel pump... loose or high resistance. When it gets hot....poof.
Could be the connector at the ecu is not seated completely.
My
02
Posted by: rjames Jul 17 2020, 11:54 PM
Robert I have a new-ish FI wiring harness and 043 ECU I can loan you for testing. Which ECU do you need?
I have a spare ECU that I will swap in tomorrow. If that doesn’t take care of it I’ll likely take you up on your offer to borrow (or rent) your FI harness for testing.
Thank you!
Posted by: Rand Jul 18 2020, 12:00 AM
Godspeed Robert. This is definitely one we need to learn the final results on. You have chased it hard and carefully to seemingly the ends. Can't wait to learn what gremlin it is. Best of luck!
Posted by: cuddy_k Jul 18 2020, 12:14 AM
When you stall, is your coil nuclear hot? Like so hot you can't keep your hand on it? If so...that could be your problem. I had that issue on my yellow car and solved it wiht a ballast resistor. Never stalled again and the coil never got hot. I know, we shouldn't need one, but...
Posted by: rjames Jul 18 2020, 10:23 AM
When you stall, is your coil nuclear hot? Like so hot you can't keep your hand on it? If so...that could be your problem. I had that issue on my yellow car and solved it wiht a ballast resistor. Never stalled again and the coil never got hot. I know, we shouldn't need one, but...
Thanks- I never checked the coil to see if it was, but I did try swapping the new Bosch blue coil I installed when I bought the 123 distributor out with stock coil when it wouldn’t stay running and it didn’t solve the issue. The new coil is back in.
Posted by: rjames Jul 18 2020, 10:24 AM
Godspeed Robert. This is definitely one we need to learn the final results on. You have chased it hard and carefully to seemingly the ends. Can't wait to learn what gremlin it is. Best of luck!
Posted by: rjames Jul 22 2020, 01:24 PM
Update to the ongoing saga..apologies in advance for the long post.
Installed a brand new ignition harness (a work of art by Jeff B) but the stalling issue remains, although it took a bit of a different shape yesterday.
After installing the ignition harness, I drove the car without any issues for ~30 minutes trying to get the AFR dialed in on the MPS. Drive, pull over, adjust, repeat. Idle always steady at 1k. When I pull over to make another adjustment, before touching anything the idle starts dipping to almost stalling the car and back up to 1k over and over as if the MPS diaphragm had just cracked. After about a minute of this as I'm wiggling wires, checking hoses, etc. While it's doing this the AFR is super lean (~16+), yet the only way I can keep it running for the drive home is to open up the throttle body screw to let more air in and stay on the go pedal. I'm only 4 miles from home, but the AFR is so high that I worry about cooking the engine so I pull over after 2 miles to let the car cool off a bit. I get impatient and after several minutes start it up again and within a few minutes of limping home the problem goes away and the car is back to normal, but when I get back in my driveway the problem returns and I can't keep the car running. I check the MPS and it's holding vacuum just fine.
Something that I noticed as it was surging was air coming out of the hole in the passenger side tin that is to the left of the distributor. At first I though a hose had come disconnected. Can't remember if I feel that air blowing when the car is running normally and since it's not running at the moment, I can't check. Maybe this is just the from the impeller?
So do I try replacing the injection harness now?
And a side question about MPS adjustment and cold idle:
I was able to get the AFR to ~ 13.4 for par load and 13 for WOT. Maybe not ideal, but the car seems to like the AFR on the rich side. However, the AFR at idle is only ~12.5-12.9. If I try to raise it by adjusting the MPS, the part load AFR is then too high. If I try adjusting it using the throttle body screw and ECU knob, the idle is too high.
In other posts I see where people have an AFR above 14 at idle.
Lastly, I have a working AAR valve, but when the car is cold the idle speed only goes up to ~1100 rpms or so. If I plug the hose the car dies, so I guess it's doing it's thing, but my understanding is that I should be seeing much higher RPMs when cold, no?
Posted by: rjames Jul 25 2020, 02:07 PM
Bump out of desperation.
Should I feel a fair amount air coming up from the engine through the tin on the passenger side? Leak at the head?
Posted by: BeatNavy Jul 25 2020, 02:11 PM
Can you be more specific about where air is coming from? Doesn’t seem right.
Sort of grasping but have you done a compression check?
Posted by: rjames Jul 25 2020, 02:45 PM
Can you be more specific about where air is coming from? Doesn’t seem right.
Sort of grasping but have you done a compression check?
It's ok, I'm grasping too. I haven't done a compression check but planning on borrowing the tool to do so tomorrow.
Air is coming from the hole in the tin just above where #4 is stamped in the tin, and also through where the CHT wire comes out of. I’m told head leaks are loud, but no abnormal sounds though.
Posted by: yellowporky Jul 25 2020, 03:17 PM
Did you ever rule out the ecu?
Posted by: rjames Jul 25 2020, 04:01 PM
Did you ever rule out the ecu?
I did
Posted by: yellowporky Jul 26 2020, 11:06 AM
If all of your components check out, replaced your FI harness and you are still having problems i would suspect the power feed to the fuel pump and the ground. It would be the only thing that you have not replaced. When cold it works and when it runs and gets hot looses connection until it cools down again.
Also when building my car i bought new relays from 914 rubber and some of them did not work when i plugged them in so i had to spread the out the legs and then was all good. Maybe you are having a loss of connection a like that?
Posted by: rjames Jul 26 2020, 03:23 PM
If all of your components check out, replaced your FI harness and you are still having problems i would suspect the power feed to the fuel pump and the ground. It would be the only thing that you have not replaced. When cold it works and when it runs and gets hot looses connection until it cools down again.
Also when building my car i bought new relays from 914 rubber and some of them did not work when i plugged them in so i had to spread the out the legs and then was all good. Maybe you are having a loss of connection a like that?
Thanks- Verified fuel pump is running and fuel pressure is at spec when it stalls,
I’m still hoping someone can tell me why I am feeling air come out the passenger side engine tin when the car is running. I’m worried there is an issue with the head seal but from what I’ve read it would be really noisy if that was the case. No?
Posted by: toadman Jul 26 2020, 06:34 PM
Can you be more specific about where air is coming from? Doesn’t seem right.
Sort of grasping but have you done a compression check?
It's ok, I'm grasping too. I haven't done a compression check but planning on borrowing the tool to do so tomorrow.
Air is coming from the hole in the tin just above where #4 is stamped in the tin, and also through where the CHT wire comes out of. I’m told head leaks are loud, but no abnormal sounds though.
On my car the hole in the tin above the #4 holds a small plastic spark plug wire guide. Also, there should be a rubber seal in the hole where the CHT wire comes through the tin. For optimum cooling you should "seal" all holes in the tin with the factory component that is meant to go there or something else. For example, missing spark plug wire seals let out gobs of cooling air.
Regarding your intermittent stalling, I read this whole thread one time and I recall that you mentioned that you checked your grounds but I don't recall you saying which ones you checked. Did you check the tri-prong FI ground on the top of the engine, the ground under the relay board behind the driver and the transmission-to-body ground on the trunk floor? My apologies if have repeated something.
Posted by: yellowporky Jul 26 2020, 06:46 PM
if he replaced his fuel injection harness the grounds on top of the engine would go with the harness
i believe a bad trans to body ground would make it hard to crank the engine when warm.
Has to be in the harness to the brain because he says everything else is new and checks good when it wont start.
The air that you are feeling blowing when the engine is running is from the cooling fan. Unless i misunderstood you.
Posted by: rjames Jul 26 2020, 08:38 PM
if he replaced his fuel injection harness the grounds on top of the engine would go with the harness
i believe a bad trans to body ground would make it hard to crank the engine when warm.
Has to be in the harness to the brain because he says everything else is new and checks good when it wont start.
The air that you are feeling blowing when the engine is running is from the cooling fan. Unless i misunderstood you.
I replaced the ignition harness but not the injection harness.
Posted by: rjames Jul 27 2020, 10:26 PM
Compression #s with engine warm, all plugs removed and throttle open:
110, 110, 130, 131
Posted by: rjames Aug 24 2020, 11:37 AM
Just wanted to dust the cobwebs off of this thread with an update. I installed a new Bowlsby injection harness (work of art!), and so far...so good. I'm probably jinxing things just by posting this. I hate intermittent issues, and given how intermittent this issue was, I won't be confident that the car won't stall on me again for some time.
Two questions remain:
1) If I leave the air temp sensor plugged in (sensor on the plenum), when cold the car runs fine, but when it warms up, the idle hunts like crazy. If I unplug it the idle is steady both when cold and when it's warmed up.
2) I can't get the idle lower than 1100 rpms. This seems to be an issue others have after installing the 123 distributor and happens whether I configure the distributor it for retard or advance. I don't have a vacuum leak, but I did notice something on both my original throttle body and the NOS one I found last year: When the idle screw is all the way in, a fair amount of air is still being pulled from the top of the butterfly. If the adjuster is all the way in, shouldn't it completely (or nearly completely) block any air from getting in?
(borrowed pic)
Posted by: BeatNavy Aug 24 2020, 03:02 PM
Just wanted to dust the cobwebs off of this thread with an update. I installed a new Bowlsby injection harness (work of art!), and so far...so good. I'm probably jinxing things just by posting this. I hate intermittent issues, and given how intermittent this issue was, I won't be confident that the car won't stall on me again for some time.
Two questions remain:
1) If I leave the air temp sensor plugged in (sensor on the plenum), when cold the car runs fine, but when it warms up, the idle hunts like crazy. If I unplug it the idle is steady both when cold and when it's warmed up.
2) I can't get the idle lower than 1100 rpms. This seems to be an issue others have after installing the 123 distributor and happens whether I configure the distributor it for retard or advance. I don't have a vacuum leak, but I did notice something on both my original throttle body and the NOS one I found last year: When the idle screw is all the way in, a fair amount of air is still being pulled from the top of the butterfly. If the adjuster is all the way in, shouldn't it completely (or nearly completely) block any air from getting in?
(borrowed pic)So I'll give you two
and one as a partial victory, pending additional info. Hopefully the wiring harness was the ticket. It would make sense. Intermittent issues could easily be caused by a sketchy wiring harness. Fingers crossed.In terms of your questions: 1) you are lean at idle. Unplugging the air temp sensor is going to somewhat richen your mixture, and the hunting idle was because it was lean.
2) I think that's normal. I'll go see if I can find one of my TB's and compare, but there are several versions of them, so I may not be able to answer that definitively. Yes, with my 2056, D-Jet, 123 Dizzy, using curve "B" I couldn't get the idle below 1100. I kind of got used to it.
Rock on
Posted by: rjames Aug 24 2020, 03:19 PM
So I'll give you two
and one as a partial victory, pending additional info. Hopefully the wiring harness was the ticket. It would make sense. Intermittent issues could easily be caused by a sketchy wiring harness. Fingers crossed.In terms of your questions: 1) you are lean at idle. Unplugging the air temp sensor is going to somewhat richen your mixture, and the hunting idle was because it was lean.
2) I think that's normal. I'll go see if I can find one of my TB's and compare, but there are several versions of them, so I may not be able to answer that definitively. Yes, with my 2056, D-Jet, 123 Dizzy, using curve "B" I couldn't get the idle below 1100. I kind of got used to it.
Rock on
@http://www.914world.com/bbs2/index.php?showuser=17042 I'll take as many
as I can get. Thanks and I appreciate all of your help along the way on this one. So maybe I should go back and re-calibrate the MPS with the air temp sensor plugged in (and engine warmed up). The perfectionist in me hates knowing it's unplugged.
RE throttle body: I found a pick of a bunch of different stock versions, including ones that didn't have the hole drilled through the butterfly plate. If I cover up that hole the engine dies (which supports my belief that I don't have a vacuum leak). However, if I cover up just a bit of the port that's associated with the idle adjustment screw, I can easily get the idle below 1000 RPMs.
I also found a thread that a rebuilder of TBs had posted here a while back saying that part of his service was to ensure that the idle bleed screw fully sealed the port when screwed in all the way.
It would make sense to me that it should function that way.
Posted by: orthobiz Aug 24 2020, 04:32 PM
Thanks rj for helping me to think about my 1974 2.0 liter running problem last year (it was the timing all along!)
Anyway, my 1974 1.8 had an intermittent problem with dropping out and stalling and it was the ignition switch. Maybe a long shot, but I didn't see you mention it. I could stop the stalling by manually holding the switch ever slightly like I was going to start the car.
I was going to try to be clever and say maybe it's your driveway since it seems to stall there a lot...
Good luck!
Paul
Posted by: rjames Nov 3 2020, 05:04 PM
Ok I'm back to updating my thread that seemingly never ends. I thought I had my problem of high and/or surging idle and/or intermittent stalling issue fixed with the new ignition and new injector harnesses.
Nope.
Car hasn't stalled again, but almost did. Started the car the other day and after it warmed up the idle was a perfect and steady 1000rpm. Which was strange since I couldn't get it below 1200rpm previously. AFR was 13.5 too, even though the last time I had driven it it was 10.5 at idle. 
Drove ~ 15 minutes to the grocery store. All good. When I got back to the car the idle was now at 1100rpm. Another 15 minutes of driving and idle increased to 1200rpm.
More time driving and the idle started fluctuating from 600-1200rpm. At one point at a stop sign the engine almost stalled- idle just dropped to almost 0 like the engine had just been turned off, but the idle came back up before that could happen.
I did notice that when the idle is fluctuating (usually going from ~600-1200 rpm) it will continue to fluctuate even if I step on the gas a bit and hold it there- say increase the RPMs to 1500rpm, the rpms will continue to drop to about 1200 and then go back to 1500. So this issue is happening even when the ECU is not seeing an 'idle' state because the TPS is seeing idle anymore.
The nagging feeling that maybe there is a vacuum leak wouldn't go away so I connected my vacuum gauge via a T off of the throttle body retard port and it shows 17.inHg at 1100rpm and when it surges to 1200rpm it reads 18.5in.Hg. Of course when I did this test the idle wasn't dropping below 1100rpm so I don't know what the reading would be then, will try and capture that. My guess is that it will be less than 17in.Hg just by virtue of the slower engine speed. In other words- I don't think i have a vacuum leak because I would expect the vacuum to drop at higher idle RPMs if that was the case.
This feels like an issue with the FI system or the engine itself. But I've got a new ignition harness, new FI harness, new CHT, 123 distributor, injectors tested, verified fuel pressure, etc. I've tried swapping ECUs and I've got a rebuilt MPS that holds vacuum. I suppose I could try putting the vacuum gauge between the manifold and and the MPS and see if the MPS diaphragm is intermittently failing? Could this be a thing?
What about the engine itself? What are the symptoms of leak at the heads? Compression issue? (Current #s are 110, 110, 130, 131) Other? Car seems to have plenty of power.
Posted by: porschetub Nov 3 2020, 06:33 PM
Ok I'm back to updating my thread that seemingly never ends. I thought I had my problem of high and/or surging idle and/or intermittent stalling issue fixed with the new ignition and new injector harnesses.
Nope.
Car hasn't stalled again, but almost did. Started the car the other day and after it warmed up the idle was a perfect and steady 1000rpm. Which was strange since I couldn't get it below 1200rpm previously. AFR was 13.5 too, even though the last time I had driven it it was 10.5 at idle.
Drove ~ 15 minutes to the grocery store. All good. When I got back to the car the idle was now at 1100rpm. Another 15 minutes of driving and idle increased to 1200rpm.
More time driving and the idle started fluctuating from 600-1200rpm. At one point at a stop sign the engine almost stalled- idle just dropped to almost 0 like the engine had just been turned off, but the idle came back up before that could happen.
I did notice that when the idle is fluctuating (usually going from ~600-1200 rpm) it will continue to fluctuate even if I step on the gas a bit and hold it there- say increase the RPMs to 1500rpm, the rpms will continue to drop to about 1200 and then go back to 1500. So this issue is happening even when the ECU is not seeing an 'idle' state because the TPS is seeing idle anymore.
The nagging feeling that maybe there is a vacuum leak wouldn't go away so I connected my vacuum gauge via a T off of the throttle body retard port and it shows 17.inHg at 1100rpm and when it surges to 1200rpm it reads 18.5in.Hg. Of course when I did this test the idle wasn't dropping below 1100rpm so I don't know what the reading would be then, will try and capture that. My guess is that it will be less than 17in.Hg just by virtue of the slower engine speed. In other words- I don't think i have a vacuum leak because I would expect the vacuum to drop at higher idle RPMs if that was the case.
This feels like an issue with the FI system or the engine itself. But I've got a new ignition harness, new FI harness, new CHT, 123 distributor, injectors tested, verified fuel pressure, etc. I've tried swapping ECUs and I've got a rebuilt MPS that holds vacuum. I suppose I could try putting the vacuum gauge between the manifold and and the MPS and see if the MPS diaphragm is intermittently failing? Could this be a thing?
What about the engine itself? What are the symptoms of leak at the heads? Compression issue? (Current #s are 110, 110, 130, 131) Other? Car seems to have plenty of power.
Obviously you did the compression test with warm engine ? you do have a high percentage variance in compression ,did you reset the valves before the test?.
Good luck.
Posted by: rjames Nov 3 2020, 06:39 PM
Yes, engine was warm when I checked the compression and valves adjusted.
Posted by: rhodyguy Nov 4 2020, 07:54 AM
A local member had the same 'hunting' (fluctuation) problem. The stacked elbow looked good but was broken in a spot you couldn't see. Have you verified the internal plenum tubes are not cracked? The bottom side as well as the top.
Posted by: Highland Nov 4 2020, 09:35 AM
I know this theory may be completely invalid, but where is your PCV plugged into? Is it the stock location? Just wondering if an aging valve can cause inconsistencies in idle performance. I moved mine above the TB. Things seems to steady out but I made a bunch of other adjustments and changes, so hard to say.
Posted by: rjames Nov 4 2020, 10:36 AM
A local member had the same 'hunting' (fluctuation) problem. The stacked elbow looked good but was broken in a spot you couldn't see. Have you verified the internal plenum tubes are not cracked? The bottom side as well as the top.
'75- no stacked elbow and no PCV.
And a vacuum leak wouldn't account for the engine almost cutting out- the RPMs would go up, plus I measured no loss of vacuum when I put the vacuum gauge on the TB, even when the idle was fluctuating.
Posted by: yellowporky Nov 4 2020, 12:28 PM
Did you ever replace the board on your TPS? 914 rubber sells them
Posted by: rjames Nov 4 2020, 01:21 PM
Did you ever replace the board on your TPS? 914 rubber sells them
No, and not discounting it, but I'm stuck on how it would explain the engine stalling since the car will still run with the TPS unplugged. I did clean the board last summer even though the contacts looked good. It's been calibrated.
Posted by: second wind Nov 4 2020, 01:23 PM
Something about the idle changing with amount of running time keeps pointing to a vacuum leak. Isn't it possible that the throttle body has a leak underneath it where it attaches to the plenum? The rising temperatures open it and then it closes again after cooling. Just had to throw my 2 cents in. Sure sounds like a vacuum leak. All the best....
gg
Posted by: rjames Nov 4 2020, 02:09 PM
Something about the idle changing with amount of running time keeps pointing to a vacuum leak. Isn't it possible that the throttle body has a leak underneath it where it attaches to the plenum? The rising temperatures open it and then it closes again after cooling. Just had to throw my 2 cents in. Sure sounds like a vacuum leak. All the best....
gg
I'm open to anything being possible at this point. However, I when I had a vacuum gauge hooked up to the TB below the butterfly while the car was idling, the gauge showed 17inHg with no loss of vacuum when the idle fluctuated up- in fact the vacuum increases when the idle RPM increases. My understanding is that vacuum at idle below the TB should be anywhere from 15-18inHG, so I'm on the upper end of that.
A vacuum leak also wouldn't explain the engine wanting to stall.
Appreciate everyone's ideas. Keep 'em coming.
Posted by: Highland Nov 4 2020, 05:19 PM
Did you ever replace the board on your TPS? 914 rubber sells them
No, and not discounting it, but I'm stuck on how it would explain the engine stalling since the car will still run with the TPS unplugged. I did clean the board last summer even though the contacts looked good. It's been calibrated.
Another WAG, but if your TPS is worn and intermittently telling the ECU you're at idle, I can see how you can go way rich or lean sporadically (depending on ecu and MPS settings) especially as engine compartment temps change.
Do you have a variable resistor between the cht and ecu? I find that adds an extra knob to dial everything in.
Posted by: rjames Nov 4 2020, 05:55 PM
Did you ever replace the board on your TPS? 914 rubber sells them
No, and not discounting it, but I'm stuck on how it would explain the engine stalling since the car will still run with the TPS unplugged. I did clean the board last summer even though the contacts looked good. It's been calibrated.
Another WAG, but if your TPS is worn and intermittently telling the ECU you're at idle, I can see how you can go way rich or lean sporadically (depending on ecu and MPS settings) especially as engine compartment temps change.
Do you have a variable resistor between the cht and ecu? I find that adds an extra knob to dial everything in.
I like WAGs.
The premise makes sense to a point, but then doesn't explain why when the idle surge is happening, the rpms continue to surge when I open the throttle a bit and hold it in that position. In that condition the TPS wouldn't be reporting an idle state to the ECU.
I don't have a resistor between the CHT and ECU. Car ran great for 7+ years without one before this issue cropped up, so I haven't felt a need to put one in. I've also got 3 CHTs that I've tried, both used and new ones. All test in spec when measuring resistance cold and warm.
Posted by: rudedude Nov 4 2020, 06:33 PM
Have you taken the tri-ground and actually taken out the case bolt and cleaned it to make sure it isnt loosing ground while warm? It seems like you have done virtually everything else. It sure seem electrical somewhere.
Posted by: yellowporky Nov 4 2020, 08:31 PM
It seems like 2 different things happening here.
The surging from what i understand tends to be a lean issue typically caused by a vacuum leak and the stalling would tend to be a heat related electrical issue.
How do the spark plugs look? Are they all colored tan or is one or more white?
Do not assume anything is good until you 100% rule it out. Go to 914 rubber and buy all of the vacuum elbows, connectors, TB gasket, cold start injector gasket ect.. Auto Atlanta has a good vacuum line kit too, Put clamps or good zip ties on the plenum to intake runner hoses and also it is not unheard of to have a crack in the plenum itself.
Check the intake nuts for proper torque too.
For the electrical issue make sure as stated above, remove and clean the 3 prong ground for the FI and then go to every other ground one by one and do the same.
Hope you find it soon. Unfortunately this is how most of us learn about these cars.
Posted by: rjames Nov 4 2020, 10:47 PM
Check the intake nuts for proper torque too.
For the electrical issue make sure as stated above, remove and clean the 3 prong ground for the FI and then go to every other ground one by one and do the sam
All vacuum hoses are new and have zip ties on them. Intake hoses are new. Gaskets for the intake runner, TB and cold start injector are new. I tore down all of the FI and intake stuff and cleaned it and checked the plenum for leaks
Used a smoke machine to hunt for any vacuum leaks. Used vacuum gauge at idle to verify vacuum was in speck (17inHG).
Bolt that grounds the 3prong connector on the FI harness was removed and cleaned up (it already looked fine but looks better now).
Vacuum doesn't seem to be the issue- at least not on the topside of the engine.
Haven't checked the ground point under the relay board. What wire is connected to it?
Posted by: BeatNavy Nov 5 2020, 06:13 AM
Robert, sorry this issue has resurfaced It's either so obvious it's staring us in the face or buried so deeply we can't find it among the usual suspects.
Those are good suggestions about the relay board. Is that in good shape? It's a little tedious, but since you've tried just about everything else, you may want to remove the relay board from the car and test continuity between the traces. As a minimum once you remove the relay board you'll see the multi-wire ground in front and below the board that it's connected to. Worth cleaning, inspecting, tightening, etc.
Not long after I picked up my '72 I went through the whole D-Jet. The relay board was suspect, so I removed that for some TLC. While I was at work my wife actually took the time to scrape all the tar off the back with a bucket of solvent so I could inspect and repair. Nasty job, bless her heart (come to think of it, that may have been the LAST thing she did for me on that car.... ). Anyway, I did end up finding some questionable connections and soldering or reinforcing those before sealing it back up again.
EDIT: Sorry, Robert, I realized initially I put a "happy face" in the first sentence. Not my intention. It's changed now in my post (anyway) to a sad face to show that I know this sucks. I'm sure that makes you feel a LOT better.... 
Posted by: rjames Nov 5 2020, 11:52 AM
Robert, sorry this issue has resurfaced
It's either so obvious it's staring us in the face or buried so deeply we can't find it among the usual suspects.Those are good suggestions about the relay board. Is that in good shape? It's a little tedious, but since you've tried just about everything else, you may want to remove the relay board from the car and test continuity between the traces. As a minimum once you remove the relay board you'll see the multi-wire ground in front and below the board that it's connected to. Worth cleaning, inspecting, tightening, etc.
Not long after I picked up my '72 I went through the whole D-Jet. The relay board was suspect, so I removed that for some TLC. While I was at work my wife actually took the time to scrape all the tar off the back with a bucket of solvent so I could inspect and repair. Nasty job, bless her heart (come to think of it, that may have been the LAST thing she did for me on that car....
). Anyway, I did end up finding some questionable connections and soldering or reinforcing those before sealing it back up again.Good suggestion- you probably can guess how I'm going to answer- I have a stack of 4 relay boards and spare relays. Continuity has tested good on all of them, although I swapped the one in the car out anyway. I will check the ground connection there though, somehow I missed doing that.
Posted by: 904svo Nov 5 2020, 12:31 PM
Just a WAG , check the ground strap from the transmission to the body
Posted by: rjames Nov 5 2020, 02:00 PM
Just a WAG , check the ground strap from the transmission to the body
Done, but keep 'em coming.
Posted by: yellowporky Nov 6 2020, 09:13 AM
Not sure it is possible to cause a stall but is your ignition switch goofy?
Posted by: rjames Nov 6 2020, 11:31 AM
Not sure it is possible to cause a stall but is your ignition switch goofy?
It's crossed my mind, but because the stalling seems to be tied to the idle fluctuation, I'm inclined to think the ignition switch is ok.
Posted by: yellowporky Nov 6 2020, 12:58 PM
So when the car is warm it idles down and stalls? Not like it cuts off.
Is the decel valve functioning? On my 73 with everything nos or rebuilt it has some strange return to idle behaviors and I just assume that it is the goofy old d-jet. When warm the engine returns to idle pretty slowly and sometimes stays around 1,200 rpm for a bit before settling down but often times the light will change and you are off again before it completely idles down.
With how off your compression numbers are you only have that remaining
A friend reminded me of the product Sea Foam the other day and he runs a can through his fuel tank every once in a while to keep everything super clean
Posted by: rjames Nov 6 2020, 01:46 PM
So when the car is warm it idles down and stalls? Not like it cuts off.
Is the decel valve functioning? On my 73 with everything nos or rebuilt it has some strange return to idle behaviors and I just assume that it is the goofy old d-jet. When warm the engine returns to idle pretty slowly and sometimes stays around 1,200 rpm for a bit before settling down but often times the light will change and you are off again before it completely idles down.
With how off your compression numbers are you only have that remaining
A friend reminded me of the product Sea Foam the other day and he runs a can through his fuel tank every once in a while to keep everything super clean
Everything is intermittent. When it does stall it stalls immediately when taking my foot off the gas pedal with seemingly no loss of power beforehand. Usually by the time I limp it home, the stalling goes away. :/
To be fair, the car hasn't stalled since I replaced the ignition and FI harnesses, but I haven't driven it that much either.
The idle surges are intermittent too. The last time I took it out, the idle was stready at 1000 RPMs after warmup. After driving it a bit, the idle crept up to 1200, but was steady. More driving led to the idle surging from 600-1200rpm. Got back home and the idle surge range changed to 1000-1200rpm.
Seems like if it was a compression issue it would be constant and the engine would be lacking power, which doesn't seem to be an issue. But maybe that's not always the case?
Posted by: euro911 Nov 6 2020, 02:02 PM
110, 110, 130, 131
Which cylinders have the low compression #s. 1. ____ 2. ____ 3. ____ 4. ____
Have you performed a valve adjustment? If not, do so, then check compression again.
I had a hunting idle on the '71 (1.7L) when I first acquired the car. I replaced all the vacuum lines, adjusted points, set ignition timing, etc., but after adjusting the valves (right bank valves were too tight, not completely seating), the hunting stopped
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Posted by: rjames Nov 6 2020, 06:12 PM
110, 110, 130, 131
Which cylinders have the low compression #s. 1. ____ 2. ____ 3. ____ 4. ____
Have you performed a valve adjustment? If not, do so, then check compression again.
I had a hunting idle on the '71 (1.7L) when I first acquired the car. I replaced all the vacuum lines, adjusted points, set ignition timing, etc., but after adjusting the valves (right bank valves were too tight, not completely seating), the hunting stopped
No points lost for not reading through the whole thread. It's a lot to go through. I thought about starting a new post that starts off with everything I've tried, but then I'd have to re-read it myself.
Valves have been adjusted.
Compression check on warm engine: cyls 1 & 2: 110, cyls 3 & 4: 131
Posted by: bzettner May 16 2021, 01:14 PM
I'm on pins and needles! What is the latest on your intense diagnosis? I'm dealing with something similar and have read all of this thru a search and I'm listening to all of it.
Posted by: rjames May 16 2021, 04:42 PM
I'm on pins and needles! What is the latest on your intense diagnosis? I'm dealing with something similar and have read all of this thru a search and I'm listening to all of it.
Good timing. I just started a new thread on this with some updated information. Spoiler alert: It's still not fixed.
New thread: http://www.914world.com/bbs2/index.php?showtopic=353502
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