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Stalling at cold start, Erratic Idle RPM fluctuation

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    Stalling at cold start, Erratic Idle RPM fluctuation

    Hello All,

    I have been having this issue for over a year on my wife's M3. It spends most of its time in the garage, mostly because I cannot solve this issue.

    Symptoms:
    Cold start - car turns on, revs up to 1000rpm.
    Idle begins to hunt form 500-1000 rpm immediately.
    After maybe 2 cycles car shuts off. Upon restart same issue happens again.
    This will continue until I hold throttle open to about 1500 RPM for a minute or two. Once the car feels like it exits open loop and enters closed look it will idle fine.
    If car is warm, restarts without issue. This only occurs during cold starts.
    I have noticed that unplugging the MAF does make this issue slightly less frequent, but not 100%

    Car has a custom Epic tune for Euro headers. I have tried re-installing OEM tune and nothing changes. No codes are thrown at all.

    I have used INPA to check an other hidden codes or non-present codes. I have read you need DIS or ISTA-D for a vanos test, but I am not 100% sure if there is anything I can check with INPA since that is the only diagnostic tool I posses currently.

    Most of the better content was on the old site, but I cannot access any of the bookmarked pages since the site was taken down.

    Any updated info anyone can share on how I can trouble shoot thing going forward? This has really gotten my stumped and I don't use the car because of it.

    Thanks all in advance!

    #2
    Maybe your MAF might be going out. I read somewhere that the MAF won’t throw codes when it goes bad

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      #3
      Interesting you mention that. I had previously unplugged the MAF and cleaned it, and forgot to plug it back in. The car idled great and I thought I had fixed it, only to realize after plugging it back in that the idle hunt returned.

      car only has 47k on it I guess I wouldn’t have expected it to fail.

      Comment


        #4
        I hve aZ4M and it stopped doing it after a thorough clean of the ITB’s and ICV, i also cleaned the air rail.

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