1990 e30 325i vert choking - only first 15 minutes

[tdennehy]

I have been driving e30s since 1990. First time I have ever had this issue, and never come across anyone else on any other forum that has found the answer.
Six months ago, my e30 developed a problem where in the first 15 minutes the car would choke. If feels as if the car shuts off and comes back, like someone quickly flicking a light switch. Recent change is I replaced ICV as car was not idling properly. ICV fixed bad idle. Yes, it is properly sealed.
Choking problem persisted. Replaced plugs - they were nasty. Took her to BMW specialist (he drives my same e30, as do others in his shop) and problem never showed itself all week when I left car with him. He is at higher altitude - unsure if that makes a difference. Bring car home. Car stalls within first minute or two in morning. Restart car. Car runs, but will "choke" a few times, for ONLY first 15 minutes of operation. Car is fine after that for the rest of the day. Can park and restart multiple times without issue. Park car in garage, and the next morning, the entire scenario starts all over again. One time I started car in and left in driveway idling for 15 minutes. Car drove fine. Weather isn't cold in Sacramento.
Replaced air filter. No change. Bottle of injector cleaner in tank. No change.
Everyone tells me it sounds like fuel problem. Does this sound like a fuel pump?

[E30 Wagen]

Fuel filter would be a cheap thing to try.

[MukeM3]

DME relay, or the ignition switch electrical base.

[Pigs]

Not sure if you're still looking for answers, but maybe my experience can help.

I have an 87 vert just over the border from you. Occasionally, it will have similar symptoms to yours, but only once per day or so. I highly suspect the transfer pump inside the fuel tank. I replaced my filter and high pressure pump (they're actually pretty easy to replace), and didn't see an improvement.

I'd start there if I were you. Post the solution when you find it.

[dnguyen1963]

Tee in a pressure gauge and monitor the fuel pressure when it is acting up.

[AndrewBird]

Could also be a crank position sensor going out. What about the cap and rotor? Contacts could be corroded. Maybe a bad coil?

[usualdeviant]

This is the issue I am having. Very intermittent. But it is a loss of spark for about 1 second. Tried new BMW CPS, BMW plug wires, Bremi cap & rotor, known good Bosch coil, wiggled my positive battery cable without seeing the trunk light flicker. I'm leaning toward the ignition switch. It is not fuel related. I have all new fuel pumps, filter. When it happens, you will see a cloud of rich exhaust behind you. That tells me fuel doesn't have a problem making its way to the cylinders. I suppose power to the fuel components may get cut for a second but there is still plenty of fuel pressure in the rail. There has to be. It only happens for about a second! It's not like it's running rough it's just a random complete loss of power. Feels like the car throws you forward in your seat for just a second. Been pissing me off. Seems like I replaced everything ignition related but the ignition switch. Oh and I also tried a reman. ECU just to be on the safe side. Also BMW main relay. Also new plugs. No dice! Anyone else had this problem? Something else I thought of is the check engine light flickers when it happens.

[jeffnhiscars]

my money is on cts

[usualdeviant]

One more thing I also have a new CTS and reman. AFM. Still no change. I suspect my wiring is all good, I've been poking around with this thing since 2010, not for this particular issue, but poking around nonetheless. All grounds are tight, even cleaned the junction block connections. Not seeing any messed up wires.

[jeffnhiscars]

you "suspect" your wires are good ?

It has to be temperature related based on your description

[usualdeviant]

Yeah I suspect my wires are ok because I've wiggled all of them connecting to the main players and I've looked at them where they are unwrapped. Maybe the thread starter but my issue happens randomly - at any temperature. Not just in the first 15 minutes. I could hook up a voltmeter to one of the wires coming off the ignition switch or wherever but I do like having spare parts for my E30. In any case I'll be trying a BMW ignition switch this weekend and we'll see what happens.

[usualdeviant]

The dealer screwed up and I won't be getting it until Monday. Just sitting here scratching my head thinking my driver's door seal definitely lets in a good amount of rain. Definitely in the vicinity of the ignition switch. One more thing I should add is the symptom is kind of like rough running now. Surprisingly the rough running is more when cold. But I still get the random complete loss of power even after warmed up. Anyone think it's my O'Reilly AGM battery?

[usualdeviant]

Well I put a new ignition switch in, the old one looked a little baked, and one of the solder joints came apart. Not sure if that was before or after I started grabbing things. But at least my left turn signal works, econometer works, and speedometer is steady now. May or may not have had anything to do with me tightening grounds behind the steering wheel.

That did not solve my problem. I removed a fuel magnet that I clamped around my fuel hose many years ago. I heard on the internet somewhere they can be good for breaking apart fuel molecules and helping it burn easier. I thought maybe it is interfering with something. Well it turns out it was interfering with something - crankshaft position sensor wiring or who knows? Because I have changed my problem. It does not happen when cold and it does not happen randomly. Now it only happens around 5k RPM at WOT. I can rev it up sky high under light throttle and it never happens. So... CPS? FPR? Fuel delivery? Fuel injectors (mine are from a Mustang)? I guess I'll be testing fuel pressure...

[punnzzells]

Dme

[usualdeviant]

DME... Not so sure since I am using my reman. one. First one, same issue. Still could be though. Tested fuel pressure today. Seems to be fine. Then I hooked up a scanner. By the way it does still act up when cold. Then I was monitoring things one at a time like engine speed, air flow, etc. It cut out at 5k rpm and it would loose communication with the scanner. It gave me a fuel pump relay code. Then later I was idling and monitoring coolant temp. It was quite erratic. The CTS on my car has a connector that does not even lock down and the wires are ones I soldered in from a Mustang lots of years ago. I know I was a crappier mechanic then than I am now so who knows about those solder joints? I did not think to wiggle the wires while monitoring the coolant temp. but I will tomorrow. Pretty new sensor though. I was watching it change from 168 to 188 in a second's time and then back again. Bled system too. Could that be my demon? Damn thing stopped cutting out at 5k. OBC relay... I just realized that was a thing. Might want to test that since it can apparently cut power to DME...