Ideas on a random no-start condition?

[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.

[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]

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?

[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]

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]

I found a new VDO for $177. Rebuilts are about $150, so...

I'm confused by that, because the first thing everyone says is spray it with carb or contact cleaner, clean out the gunk, get it to rattle, yada yada.....

We were making good progress until school and homework and HS soccer changed everything. He doesn't want me to work on it without him so things have slowed. And now the garage is pretty damn cold! We'll rig up a heater and work on weekends when we can.

Suspension next - I want it to run perfectly first.

[bddog]

ICV. They are a little spendy , just keep the carburetor cleaner away from them. Tends to melt the insides. You can buy rebuilt AFM most anywhere these days. The penny goes next to the ICV on the intake side.
This car has been sitting this long waiting on a penny?

[LateFan]

Went ahead and ordered a new ICV. It passed all tests but it's obviously not working right.

[LateFan]

Bump for update and some more questions.

As we said earlier, we have a new lift pump installed. We put a fuel pressure gauge on the driver's side shock tower. It reads about 39 psi when jumping the relay to run the pumps. Same psi at start-up. It held pressure for several weeks, say 35 psi for a week or two, then slowly dropped off.

The fuel pressure regulator was a working used one from a r3v member. I assume it's good.

We replaced the main, fuel pressure, and o2 sensor relays with new.

I pulled the AFM to clean and test. As part of that process I learned about member Gregs///M and his rebuilding service, and the very limited testing you can do with a DMM. We did check the temp sensor and got normal resistance readings.

The AFM flap is quiet and smooth. (Should we hear the wiper arm dragging on the track at all?)

So - tonight we put it back together and it started right up in a cold (20 degree) garage. Some stumbling from being cold and not running for several weeks, but it warmed right up. No idle cycling, smooth idle, starting at 900 rpm. Fuel pressure about 36.

Temp gauge straight up normal.

Idle began to climb steadily, eventually hitting 1200 to 1300. We ran it for a good 15 minutes or more, looking for vac leaks etc. Fuel pressure about 31 to 32.

After a long time, the idle began to cycle (ICV should probably just go). When the idle drops, it seems more like the engine is shutting off, then catches itself and surges up again. The mileage gauge on the dash shoots across like the engine is off, then catches.

Since we figure the ICV needs to be replaced anyway, what the hell, let's fiddle with the adjustment screw! I turned up to 2 turns out, and the cycling became faster. From zero, I went 2 turns in, and the cycling stopped. Idle still at 1200. Interesting - what does that mean?

At about 20 minutes, it just shut off. It's like turning the key off, no stumble or anything, it just shuts off. Wouldn't restart. Fuel pressure stayed at 36-ish. I wasn't watching it when it died.

I also have some AFM questions - the seal / plug on the adjustment screw is gone. Does it seem likely that someone has been messing with it, trying to make it idle correctly? I checked the tension on the screw and it's loose - no resistance at all. I turned it a couple of turns while idling with no change. Set it back where it was.

Thanks for your patience - is this simple and I'm not doing something basic?

[603Racing]

You may save yourself time/money by checking fuel pressure. The gauges are usually very cheap or free to rent.

[LateFan]

Fuel lines mostly new - just the few by the in-line pump to do.

New filter. In-line pump was intermittently noisy, likely working too hard due to in-tank pump failure. May change it soon as well to be safe.

Have not checked power to pump yet, nor fussed with DME. (Maybe I'm avoiding DME issues..)

Early on, we checked for free movement at AFM, but now I've read about the track causing problems, so we'd better recheck that.

Thanks -

[Holland]

Check your AFM. I've been having similar symptoms on my M10. Entire fuel system is new, and now I believe I have tracked the problem to a malfunctioning AFM.

[Scallywagon]

Fuel lines clogged up?
In-line filter/pump deleted?
How's power reading to your pump?
What does the multimeter say at the DME pins?

[dsphil]

I had the same problem before. I replaced the coil as well, but didn't help. The last thing I did was giggle the harness around trying to reinstall the ecu. after that, I haven't had this issue since. the second last thing I did was the main relay but that didn't solve the problem. So I think the harness might be bad. I electrical taped the harness like mad so it won't move. So give that a try. good luck.

[LateFan]

Yes, we did - the main relay (white) and the fuel pump relay next to it.

My coil numbers are:

.9 to 1.2 ohms from + to - (it cycles up and down as far as .7 to 1.5)

5470 ohms from center post to +

Bentley says .5 ohms and 5000 ohms, and to replace if higher primary or secondary resistance.