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

[Mark Henry]

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.

[Rand]

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.

[rjames]

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.

[rjames]

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.

[rjames]

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?

[rjames]

Bumping the thread to break the silence of the crickets.

[iankarr]

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.

[rjames]

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.

[mepstein]

Fuel filter or tank screen?

[rjames]

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.


.

[bzettner]

I read thru this yesterday but can't remember if you've rechecked the fuel pressure recently?

[JOEPROPER]

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.

[rjames]

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?

[BeatNavy]

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...

[DRPHIL914]

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.

[rjames]

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.

[914_teener]

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.

[rjames]

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.

[BeatNavy]

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.

[JOEPROPER]

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.