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    Cold start rough idle

    E46 M3 with Carbon airbox, CSL camshafts and CSL code in the DME on a 188k miles.

    The car has been sitting on the drive overnight. The outside temp was 5°C / 21°F

    The start up engine idle is rough as hell. The engine hardly responds to throttle pedal input and has to be coaxed into speeding up, as can be seen here: https://youtu.be/Vnb-RJRhBQ8

    DIS reports error codes misfires on cylinders 1 and 2 both without and later with 'cutout'.
    Eventually multiple cylinder misfire will be recorded if i don't turn the engine off. The DIS misfire counter shows around 57 misfires for cylinder one and 7 for cylinder 2.


    If i turn the engine off and back on, the idle is much better as shown here: https://youtu.be/XMD-CYYB_4c​

    Quickly jabbing the throttle pedal produces an immediate response unlike before. However, it does take a short while to settle back to idle.


    Once the engine had warmed up, i did a DIS Vanos test which passed -


    Apologies for the audio quality. It's the first time i have used my phone to take a video.

    I did have the cylinders compression tested several months back anmd was told they were ok. I've purchased a decent compression tester to verify this though.

    I have moved the coil packs and fuel injectors around to see if the fault moved but it hasn't.

    Has anyone experienced a similar issue?
    Last edited by ac427; 02-15-2025, 07:51 AM.

    #2
    Was the compression test done with all the spark plugs out?

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      #3
      Fuel trims fine?
      http://www.natehasslerphoto.com
      '99 M3, Hellrot/Sand Beige, slicktop
      '01 M3, Imola/black

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        #4
        Originally posted by Slideways View Post
        Was the compression test done with all the spark plugs out?
        It was done a by a BMW specialist so i woul dhave thought so. I can ask.

        Comment


          #5
          Originally posted by Nate047 View Post
          Fuel trims fine?
          I'll double check but they were near 1.0 when i have looked previously.

          Could this issue be vacuum related?

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            #6
            spark plugs and/or coils. try to switch the coils with other cylinders and see if the misfire moves to these.
            2003 AW/BLK 6MT - Instagram

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