Ideas on a random no-start condition?

[LateFan]

New ICV installed a few days ago. Runs much much better. The old one rattles when shaken, but not near as freely as the new one.

Still has some idle issues :

Once it's warm, it idles very low, like 600 or less.
You can't rev and drop the throttle - it will die every time.
If you lower the throttle verrry slowly you can get it back down to idle (low).
As it warms up, the idle sometimes cycles a bit, say from 900-1000 (but this could be a searching idle if the throttle plate isn't shut yet)
Restarting is very difficult or you have to leave it sit for awhile before trying again.
It stalled three times last night - had to drive it home feathering the brake and gas pedals together (auto trans).
Fuel pressure starts out higher when cold, about 40psi. When warm, it's at 31.5 to 32 when idling. When you rev it, the psi drops - when revs come back down, pressure goes back up.

Where do we look next?
AFM worn? (175k miles)
AFM idle air screw? (cap seal is missing)
Idle Control Module? (but the ICV works, and it's downstream of ICM)
Adjust valves? (head was replaced 5k ago by PO, so I didn't do it - they seem quiet to me, no sewing machine.

I'm getting a bit over my head and I hate to just replace parts randomly - ideas?

[LateFan]

Saturday BUMP!

Any ideas on what to check next? It is -6 and very windy outside, so nothing is happening this weekend! A college football playoff game is about to start 8 blocks away - can you imagine sitting on aluminum bleachers?

I'm thinking about sending our AFM to Greg to rework it - maybe that's just to eliminate another possibility.

I have not adjusted the valves yet, since I figured they were just done when the head was replaced. But they're fairly quiet - what is the effect of valves too tight?

[LateFan]

With a new ICV and Greg's rebuilt AFM, it started and ran beautifully on Xmas day. Felt like we had finally solved it.

Another day we started it and it stumbled, missed, blew black smoke, and stalled. Wouldn't re-start.

Yesterday we finally adjusted the valves to .010 cold, and put some black RTV on the (new) rocker plugs as they seemed to be hissing in a smoke test. Cleaned the sooty plugs (again). Left the battery unhooked to make sure it had re-set.

If this is a clue, the fuel pressure had dropped off to almost nothing over a few days.

Today we tried again to start it. Started up but ran poorly right off the bat. Missing, stumbling, black smoke. A bit of throttle made it stumble worse. Smoke alarms went off with the garage door open.

Out of curiosity about air leaks, I pulled the oil cap....zero change in idle (?) Isn't that pretty odd? It usually nearly kills it. So then I pulled the brake booster hose off the intake as I suspect the booster grommet as well. As soon as the hose came off the nipple, the idle shot up. When I plugged the hole with my thumb, it stalled. Didn't try to re-start.

Fuel pressure when cranking was 40, it ran at about 32, and it showed 35 after shut-down. An hour later, it's at 15. Visually checked the DME and ICM for obvious problems - it's all original and untouched, the cover's never been off, harness looks fine, ICM doesn't smell burned.

So what's going on? Correct me if I don't have this right - mixture can be affected by air leaks, incorrect 02 signals, incorrect temp sensor signal, fuel pressure regulator leaking into the manifold, bad AFM, bad DME (random?),.... what else?

What am I doing wrong? Air + Fuel + Fire, right? We have spark, we have air, we seem to have too much fuel. Could the 02 sensor be bad right out of the box? Would it do all this?

[TC Baur MD]

Your hard start issue might be caused by intermitant leaky injectors. I had a similiar problem with my 325i and ended up replacing my injectors with newly rebuilt E36 injectors. Problem solved. Don't know if that's an option with the 325es.

[LateFan]

Yes, possible cause. These were rebuilt and tested by r3v member MEPEH recently. It has since run perfectly, and then barely at all.

I've ordered a new fuel pressure regulator to replace the used "worked fine when removed" FPR I put on earlier. If the pressure is dropping to zero after a short time, that's either the FPR or the fuel pump check valve as far as I understand.

I think I'll test the brand new Bosch o2 sensor we put on - does that make sense as a cause for a lot of this? Intermittent bad signals from the o2? I also just bought a spare DME with 110k miles to try, but only one fix at a time so we know what did it.

There could be an air leak we missed somehow - not sure where, every hose and fitting was replaced and I did two (home-made) smoke tests. That's how I heard the valve cover rocker plugs hissing.

< EDIT > - TC, I just read your thread about the OBC wiring causing a no-start. Interesting and freak problem if you ask me, amazing you found that. Does anyone know if the '86 ES has this same wiring for the OBC?
Thanks -

< Edit the EDIT > This OBC relay will cut off both fuel and spark it sounds like. We have plenty of fuel.

[LateFan]

Update..

Installed a new FPR. Started instantly - smooth idle, warms up fairly fast and drops to about 700 rpm. Re-started just fine.

Two days in a row, so maybe we've finally beat the odd day / even day thing.

Running fuel pressure is about 31-32 psi. Stayed in the 30s after shut-off, then started dropping after an hour. Next morning it was at 5 psi. Rebuilt injectors, no external leaks, new FPR........looks like I'm ordering a new pressure pump.

[///M42 sport]

no start no crank 325i '92

So this happened suddenly at a intersection. started with a irractic idle and loss of power. Limped it over to parking lot and died. Tried restarting car but then no crank. Disconnected battery and got engine to crank but then irractic idle and died again.

Tried stomp test 1444 = which equals no issues.

I'm think its a combination of problems right now. But weird that would not even crank

[Milehigh30]

Latefan any updates. I've had almost the same issue and its time i need get to figuring it out. did the fpr fix it?

[LateFan]

Not much to report - the car is up on jacks - we're rebuilding the suspension and replacing brake hoses.

I think the ICV AND the FPR were bad or failing, which was part of it. The fuel pressure still drops overnight, which makes me think the main fuel pump check valve isn't working. We have a new pump to go on when we have the back up to flush brake lines.

I still think we have some kind of intermittent vacuum leak somewhere - most symptoms point that way. Maybe the brake booster or o-ring, maybe the vapor canister hose system... My home-made smoke tester may have missed something.

[LateFan]

Update -

We finished installing the suspension, and it's beginning to warm up outside so we can get some work done.

The car ran perfectly for a week. Like a new car. The smoothest idle, everything fine. Drove it 20 miles one day - perfect.

BUT, we never really fixed the problems, so we don't trust it yet.

Today we were taking it in for an alignment, and it wouldn't start. Same issue - black smoke, sputtering, barely idles. He took off the oil cap, and there was no idle change - doesn't that tell us something?

I'm thinking there's an intermittent big air leak somewhere -
Brake booster / vac check valve / o-ring at master cylinder?
Charcoal canister system?
Intake manifold gasket? (PO had a new head put on 5000 mi ago)

Bad o2 sensor?? (Brand new Bosch)

Would a cold start valve just decide to spray fuel when it's not supposed to? We replaced the temp-time switch.

We're taking it in for a "professional" smoke test Monday - maybe we're missing something. But if it's running well, how will they find the vac leak?!


To help others, the ICV was a big fix for idle problems, as well as a fuel pressure regulator and Air Flow Meter. We clearly had several things going on at once, and a lack of maintenance by POs.

[LateFan]

Put a new main fuel pump in last night. Fuel pressure now in the 36 range, which seems good. Started fine this morning, went for a short drive and it crapped out again. Wouldn't re-start. It almost kicked, but sputtered and blew clouds of black smoke.....?

I looked at realoem, and our brake booster vac line and fittings look totally different than those diagrams. We have a simple threaded fitting on the intake manifold forward of the throttle body, and a vac hose to a (new) 90 degree check valve at the booster.

Also - If the fuel vapor canister purge valve isn't functioning, isn't that sucking air right through the canister into the intake?

"Real" smoke test monday.

[Frankus12]

my idle creeps all over when cold, im led to believe its my ICV, which cant be adjusted in to spec, to which bentley says that means its broken. I wish you had not said you got the AFM rebuilt, because that would have been my guess. a worn afm could send an abrupt high air volume signal to the dme, causing the very rich condition it seems youre experiencing..building off that though, it certainly seems to me like a rich condition, or just timing that completely shifts for some reason. You got the timing sensors changed, ICV (have you adjusted it per bentley procedures with ampmeter?), AFM, everything physically seems good. So heres my guess,

Sorry if this was mentioned already; You said you did all the temp sensors but the dash one, so you should have replaced a total of three. The ETA has two thermotime switches (they have different names cant remember tho) one controls timing and injection, the other controls the cold start injector. On mine, the one that does timing has two visible male/female connections, no bosch connector. if you have not replaced the one that does timing, I would immediately check on that, and the wiring all around that area as well. When the problem is occurring, (or not) take those connectors and put them together to simulate a closed switch, and see if that does anything and vice versa. This switch has made my car incredibly dificult to start when warm and sometimes cold. I know how unlikely it is, but I wouldnt rule out a bad DME or icm yet, seeing youve practically done everything else. Are you in PA? A red flag here should be the way it just shuts off sometimes, to me thats an electrical failure or a sensor grounding when it shouldnt or something, bad wiring or grounds somewhere perhaps. jiggle all your wires everywhere lol, you might be surprised, i know i was when I got mine running by slapping the relays under the dash cover.

[LateFan]

Good ideas.

I believe we changed all 4 temp sensors - I'll check the receipts to make sure. Your sensor test makes sense.

My son is just now putting in a spare DME with 115k on it from a r3v member who did a swap.

He's also cleaning the plugs as I'm sure they're badly fouled, before we try another start. He just came in - first one is wet, sooty, and smells of gas. Have not touched the new ICV - idles really smoothly now when it's not doing the flooded thing.

PA 'cuz you want to come save us, or because your cars all rust and short out?! It's a dry N Calif car, now in dry Montana.

Sorry I'm so frustrated with this thing - I promised him we were buying a really reliable German car..... I have a '67 Alfa that always starts...what is up with this thing?!

[Frankus12]

Yes, sorry I understand. Just wondering Pa because if you were close I wouldn't have minded swapping dmes as I barely drive while at school.

[LateFan]

Well, that's nice of you - thanks! (but my wife's parents were both from Lancaster County / Lititz / Kutztown)

We checked the temp sensors. Three have been replaced. The fourth I believe is the dash gauge sender, which works fine so far. It has only one contact in the plug connector.

Plugs cleaned, spare DME installed. Supposed to be warmer tomorrow - we'll lift it up and pull the o2 sensor and check the wires, try the torch test.