fresh tune-up, weird idle

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  • crash n' burn
    Wrencher
    • Nov 2014
    • 211

    #1

    fresh tune-up, weird idle

    So yesterday I adjusted my valves, cleaned my ICV, and I threw in a new set of plugs as well as a new O2. The rest of the ignition system has been replaced, along with a new coolant sensor. My car has been running decently, although a little rich. She started right up and driving around I was averaging 11L/100km; down from 13.8L/100km.

    Runs great, revs very smooth, pulls well throughout the acceleration; noticeable gains back on the low-mid range power(Butt dyno). My problem is that now I have a wandering idle. I had a slight issue prior but it only would do it 2 or 3 times, then settle out. Could I have messed up my ICV?

    Or is this the typical case of fix one thing, discover another? Haha
    -89' 320iT, Brilliantrot
    -15' 320i, Glacier Silver Metallic

  • 3vilE30
    Grease Monkey
    • Jan 2013
    • 344

    #2
    Unplug the 02 sensor to force it to run open loop and see if your idle improves.
    If it does then you can rule out ignition problems, ICV and focus on sensors specifically the 02 and temp sensors. New parts can often be bad, also a smoke test wouldnt hurt.

    Did you make sure the plugs were gapped to spec?

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    • crash n' burn
      Wrencher
      • Nov 2014
      • 211

      #3
      Absolutely. Hell, replacing the temp sensor alone made the car drive 100x better. I'd hope the new O2 wouldnt be bad, it's really cut down on how rich the car has been running. Getting ~21mpg now as well.

      Could be vacuum related?
      -89' 320iT, Brilliantrot
      -15' 320i, Glacier Silver Metallic

      Comment

      • 3vilE30
        Grease Monkey
        • Jan 2013
        • 344

        #4
        The 02 shouldn't be bad, but they are known to have defects on some batches.

        How would you describe the problem?
        Is it hunting between 600-1500 rpm or around that?
        It could possibly be just the ICV.

        Comment

        • crash n' burn
          Wrencher
          • Nov 2014
          • 211

          #5
          More like 800-400. I'm only guessing since the tacho is inop. Idles down far enough that the lights dim from the voltage drop.
          -89' 320iT, Brilliantrot
          -15' 320i, Glacier Silver Metallic

          Comment

          • 3vilE30
            Grease Monkey
            • Jan 2013
            • 344

            #6


            Follow this guide.

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