Inconsistent Stall at Idle

[nadodude111]

Hey everyone,

Ya boy is back with a new mysterious condition and I need some help narrowing down the possibilities. The car will die when I come to a stop (traffic or stop light). All the lights in the cluster illuminate at this time as if putting the key to ACC without turning over. I can put the car in neutral and restart the car and it drives away just fine. Happens about once or twice a day and then will idle just fine at stops other times. Car is an automatic and drives great up to redline and WOT.

I just completed a 3500 mile road trip and the car developed an issue where it would cut power rapidly and the CE light would illuminate and then quickly return back to normal driving speed on the freeway. Was getting code 1262 which had something to do with the ICV so I cleaned it with carb cleaner and that fixed the power cut issue as that hasn’t happened in days, but now this idle issue has emerged. No check engine codes to diagnose. Perhaps I clean the ICV and AFM again?

thank you,

[82eye]

i'm thinking first check vac leaks or iacv is at fault.

[nadodude111]

Hi 82eye,

Thanks for your help. I went and thoroughly cleaned the ICV and AFM again then reset the ECU. I also “taught” the ECU to idle by idling for 10 minutes, turning the car off then going for a long drive at various speeds to teach it driving styles. While it idled, I unplugged the ICV and the revs lowered to about 500. Reconnecting the ICV brings the idle back to 700 RPM so I think the ICV works. We’ll see if this cleaning and reset works this time.

Unplugging the AFM while idling just turns the car off. And disconnecting the TPS does nothing to the car while idling or giving it gas. Not sure if these matter.

[82eye]

Hi 82eye,

Thanks for your help. I went and thoroughly cleaned the ICV and AFM again then reset the ECU. I also “taught” the ECU to idle by idling for 10 minutes, turning the car off then going for a long drive at various speeds to teach it driving styles. While it idled, I unplugged the ICV and the revs lowered to about 500. Reconnecting the ICV brings the idle back to 700 RPM so I think the ICV works. We’ll see if this cleaning and reset works this time.

Unplugging the AFM while idling just turns the car off. And disconnecting the TPS does nothing to the car while idling or giving it gas. Not sure if these matter.

it's kind of back to the beginning. check for vac leaks, a smoke test would be a good idea. icv, afm, fpr could all have something to do with it. we are seeing more and more issues traced back to icv and afm as these cars age, often they seem to be operating normally but are in various states of failure.

as far as resetting the ecu - obd1 is not near as adaptive as later versions of obd2. it doesn't actually "learn" so much as it falls back on predetermined set values as conditions change.

edit: have you experienced any hard cold or hot starting issues ?

[nadodude111]

Yep, that makes sense. I’m sure I gotta replace something, but the issue I’m having makes it hard to know what to replace. It starts, runs and drives perfectly cold or hot. The stall when coming to a stop is random. I’m prone to think (and probably wrong) that if it were a vacuum leak, which is always there, that the car would always stall at idle. The inconsistency of the stall and it’s development after a long road trip drives me to think it might be electrical and that’s something I really can’t repair as that’s beyond my skill and experience level. And since it runs and drives just fine, a mechanic won’t believe me and/or would have to daily it to finally see what I’m talking about… But yes, if the car stalls again, then the first thing I’ll do is get a smoke test.

Not ideal, but could the transmission be failing to keep the engine engaged when coming to a stop? Imagine a scenario where the constant is a perfect working car and the variable is a new driver learning to drive a manual car and incorrectly timing the clutch with the gas when coming to a stop- the car just dies but then starts right up and continues on after a restart and correct cutch use. That’s exactly what this feels like.

I do have an another AFM that I took from that ETA I found in the junkyard. Are AFMs interchangeable between early and late E and I cars?

Fuel pump relay is definitely a possibility, but I think it has something to do with the ICV. Cleaning it resolved that weird loss of power issue it developed on the road trip and all that’s left is the idle issue. So that means I’m getting hot in finding the cause…

[82eye]

stalling while coming to a rolling stop is most closely associated with a bad iacv. it might not be that but if you go through the threads you will find that is the most common cause in that scenario.

edit : stumbling or having trouble coming off throttle is often iacv as well.

[82eye]

. Are AFMs interchangeable between early and late E and I cars?

no. not supposed to be, but they will work to a degree. e and i afm part numbers are different. part numbers for the 323i and 318i are also different from the others.

[nadodude111]

stalling while coming to a rolling stop is most closely associated with a bad iacv. it might not be that but if you go through the threads you will find that is the most common cause in that scenario.

edit : stumbling or having trouble coming off throttle is often iacv as well.

If it’s the ICV then this will be the easiest repair in the world! I’ll order a new one if it keeps acting up.

THANK YOU so much for you help. You really should be charging for all this valuable knowledge.

[82eye]

If it’s the ICV then this will be the easiest repair in the world! I’ll order a new one if it keeps acting up.

THANK YOU so much for you help. You really should be charging for all this valuable knowledge.

see if you can borrow a good one to try rule it out.

only know what was taught to me here and on other forums and applied on my own car. i'd be sunk if others hadn't helped me along. we all need to keep the knowledge going.

[nadodude111]

Update: cleaning the ICV and the AFM again thoroughly cured the random stalling. I’m sure eventually I’ll need a new ICV but that seems to have fixed the issue entirely. Thank you for the help!