Cold Start Issue: Wont hold idle after ~30sec SOLVED

[M-technik-3]

I had an issue with my car where it would die at idle (when warm).

I was thinking I was getting it going with starter fluid, but my mechanic swapped the sensors on the bell housing (one for tach, and one for spark timing) and haven't had the issue since.

Can you verify if your issue is fuel, or spark?
(I thought I was getting spark, but that was still the issue.)

You have an Eta, i's don't have these but the E30 M3 does. Older system, i's use the reference sensor on the front of the crank vs the flywheel sensors.

[Tinkerer007]

I had an issue with my car where it would die at idle (when warm).

I was thinking I was getting it going with starter fluid, but my mechanic swapped the sensors on the bell housing (one for tach, and one for spark timing) and haven't had the issue since.

Can you verify if your issue is fuel, or spark?
(I thought I was getting spark, but that was still the issue.)

[2mAn]

Bump

Went home and it fired up in the afternoon and didnt give me much of a headache and drove fine to work today. It still had the hiccup, but I was able to power past it. She didnt die and got up to temp. It seems to be an occasional serious issue, but its an issue nonetheless, so I want to get it done sooner than later. Its only going to get colder from here, so Im assuming this will only get harder until its fixed

[2mAn]

If it was me personally I'd start with replacing fuel filter since its cheap enough and testing the fuel pump to make sure its pushing the correct amount of fuel. Id also check the regulator. It does definitely sound like a fueling issue.

Yea the Fuel Filter and fuel lines are good maintenance parts and wouldnt be a waste, but I doubt this will fix the problem.

There has been a rash of these types of issues lately (including on our ETA) and in many cases its the CPS so that has become my goto suggestion.

Really?... a Crank Position Sensor? never thought of that one.

Are there any other sensors I should look at replacing?

[jeffnhiscars]

There has been a rash of these types of issues lately (including on our ETA) and in many cases its the CPS so that has become my goto suggestion.

[ThatOneEuroE30]

If it was me personally I'd start with replacing fuel filter since its cheap enough and testing the fuel pump to make sure its pushing the correct amount of fuel. Id also check the regulator. It does definitely sound like a fueling issue.

[2mAn]

Hey all, bought my 325i a few weeks ago and its been good overall, but Ive been having a cold start issue.

Symptoms: At initial start-up it fires up immediately and purrs at ~700rpms. No bouncing or hunting at all. Then it will just die. It will have some trouble starting after this, but eventually when the car is warm the issue goes away. My temp solution was to hold the "idle" at ~1500rpms initially, then 2500-3000rpms more recently to speed up the time to get it to operating temp. Also, if it tries to die, sometimes I can power through it. This seemed to be work while I tried to chip away at it, but today it got the best of me and now Im asking for R3Vs help...


What Ive done so far: When it first happened I did some searching and asking around and the consensus was to change the Coolant Temp Sensors. I ordered both the one for the cluster (Brown) and the DME (Blue) since they were cheap and a 5 minute job to change. I got them through Blunt and we decided of the many options to use a Bosch sensor for the DME. This seemed to slightly change the "attitude" of the issue. Prior to the change it would be a softer stumble and ultimate death. After it seemed like it was a stronger death and I couldnt recover it. This is where I increased the rpms from ~1500 -> ~2500 and I could basically warm the car up faster and I had a better chance at fighting off the death.

Today, it wasnt cooperating at all. The car was parked for 3 days while I was gone for the long weekend. Same story, it fired up immediately, I held idle at 2500 then after ~30seconds: death. typically it comes back to life soon after a few tries. Today it didnt want to, and even when it would finally come to life, it would almost immediately die and there was nothing I could do to save it. I wasnt able to warm up the car and eventually threw in the towel and took the Roadster to work.

My guess I strongly feel this is fuel related. The starter looks new and she cranks over hard and consistently. All the ignition related parts look new too, but the fuel injectors look old and are dirty. I was planning on doing the 4-pintle Mustang injector + Sssquid Chip soon, and Im tempted to do this ASAP, but I also dont want to throw parts at it and hide the true problem.

So where should I start?