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M20B27 Inconsistent power band, help!

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    M20B27 Inconsistent power band, help!

    My 1987 eta is doing something that I'm not quite sure how to explain, so bear with me.

    It feels like a turbo lag would except it happens over and over during acceleration. Like mini power boosts 4-5 times to redline. Like maybe all the injectors were clogged and then suddenly they're not. I hope that makes some kind of sense.

    When this has been a problem before it would go away after the initial "lag" during acceleration. But now it's over and over throughout.

    I have the Miller chip installed but it did it as well with the OEM chip so I'm ruling that as non-suspect.

    My thoughts are maybe bad o2, fuel pressure regulator, vac leak somewhere on the intake, or perhaps a rusty barn door on my AFM.

    I'm going to send my AFM to Bav Rest here soon, but before I do that and spend a lot of money narrowing it down I thought maybe someone knew right off the bat that could save me the time and money.

    It's worth noting that this is my first post because when ever I have a problem it's already been answered on here 10x over. There is such a wealth of knowledge here and this is the first time search has let me down.

    THANKS in advance!

    -John

    Relevant things I've recently (within last 2 months) replaced:
    • Air filter
      Fuel Filter
      Plugs
      Plug wires
      Every engine gasket/seal/plug except head
      Catalytic converter
      Injectors were replaced a year ago

    #2
    Check fuel pressure. Pumps might be dying/dead(in tank) or fpr isn't functioning.

    Sent from my VS985 4G using Tapatalk

    Comment


      #3
      Thanks for the reply, where is the best place to put a T in?

      Comment


        #4
        Right before the fuel rail. Get a short piece of fuel line from autozone/advance and T in like that.
        AWD > RWD

        Comment


          #5
          smoke test... or double check every vacuum line. My m20b25 has the same issue at times and I'm trying to hunt down vacuum leaks

          Comment


            #6
            Disconnect the O2 sensor in the passenger side engine bay. Run it with out the O2 sensor to use the stock maps. Hesitation should go away and will indicate bad O2 sensor. I ran my car like this for a few months before I could get under it and replace it in the sub-zero temps in the winter.

            If it is the O2 sensor you can buy this one and splice it in to the old harness with crimps (not solder). This is the same Bosch "Mustang" sensor with a non-bmw plug. Got to love the BMW tax.

            sigpic
            1987 325e Lachssilber w/ MarkD chip and late bumpers, Zender EVO spoiler, s3.25 LSD

            Originally posted by nando
            I don't think there's really strong evidence that ZDDP harms cats.

            Comment

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