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

[rjames]

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?

[timothy_nd28]

What was your AFR last year?

[rjames]

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.

[BeatNavy]

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?

[rjames]

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.

[BeatNavy]

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...

[StarBear]

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.

[rjames]

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?

[rjames]

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.

[dr914@autoatlanta.com]

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?

[rhodyguy]

2.0 Djet. I think a 123 distr.

[914_teener]

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?

[rjames]

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

[914_teener]

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

[rjames]

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

[rjames]

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.

[BeatNavy]

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.

[rjames]

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.

[rjames]

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?

[BeatNavy]

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 (IMG:style_emoticons/default/sad.gif)