Car stalling AGAIN, Updates- none of them good. Options

[rjames]

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. (IMG:style_emoticons/default/rolleyes.gif)

[BeatNavy]

No problem, Robert. Boy I hope that wiring harness improves things. Definitely check ignition harness while you’re at it.

Good luck! (IMG:style_emoticons/default/beer.gif)

[logica]

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.

[bgconsul]

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.

[rjames]

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? (IMG:style_emoticons/default/confused24.gif)

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. (IMG:style_emoticons/default/smile.gif)

[second wind]

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

[rjames]

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. (IMG:style_emoticons/default/WTF.gif)

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).

[yellowporky]

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.

[rjames]

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.

[yellowporky]

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

[rjames]

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.

[BeatNavy]

Robert I have a new-ish FI wiring harness and 043 ECU I can loan you for testing. Which ECU do you need?

[914_teener]

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. (IMG:style_emoticons/default/WTF.gif)

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

[rjames]

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!

[Rand]

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!
(IMG:style_emoticons/default/beerchug.gif)

[iankarr]

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...

[rjames]

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.

[rjames]

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!
(IMG:style_emoticons/default/beerchug.gif)

(IMG:style_emoticons/default/beerchug.gif)

[rjames]

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. (IMG:style_emoticons/default/confused24.gif)

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?

[rjames]

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?