iX ... weird revving pattern

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  • EA8
    Grease Monkey
    • Oct 2008
    • 328

    #1

    iX ... weird revving pattern

    Just within the past couple of days I have noticed the engine revving around 1500-1700 when the car is in neutral, but once I shift into gears, the revs drop down to around 800 or so (which is normal). this all happened after I did some maintenance (oil change, fuel filter and cleaned out my ICV).

    Before any of this, my idle revs would jump around between 700 & 1200, which is why I decided to clean out the ICV and it seems to have cured the jumping around issue, but now I am lost as to why the revs are the way they are.

    Any assistance? Ideas of what the hell is happening?

    Cheers
  • jlevie
    R3V OG
    • Nov 2006
    • 13530

    #2
    My first suspicion would be an intake leak.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

    Comment

    • gearheadE30
      No R3VLimiter
      • Jun 2007
      • 3734

      #3
      Yeah, probly a vacuum leak. Check everything that you touched while you were in there first, but the leak may have been the cause of your idle issues in the first place.

      Project M42 Turbo

      Comment

      • EA8
        Grease Monkey
        • Oct 2008
        • 328

        #4
        I have already went through and checked all the intake parts from before and nothing so far ... is there anything else it could be??

        thanks fellas

        Comment

        • JGood
          R3V OG
          • Jan 2004
          • 7959

          #5
          Is the car automatic?

          Sounds like the ICV may still be bad. Do you have access to a known-good part to try?
          85 325e m60b44 6 speed / 89 535i
          e30 restoration and V8 swap
          24 Hours of Lemons e30 build

          Comment

          • EA8
            Grease Monkey
            • Oct 2008
            • 328

            #6
            Originally posted by JGood
            Is the car automatic?

            Sounds like the ICV may still be bad. Do you have access to a known-good part to try?

            car is a manual ... I will go through and double check everything once more. Maybe I'll even take everything apart and put it back together carefully.

            the thing that is confusing is that this intermittent.

            I'll keep you guys posted

            Comment

            • EA8
              Grease Monkey
              • Oct 2008
              • 328

              #7
              I just went through and took it all apart and tightened everything back together carefully with new hose clamps and still same issue. I am going to run some fuel injector cleaner through it over the next couple of days and see if that helps at all.

              Comment

              • JGood
                R3V OG
                • Jan 2004
                • 7959

                #8
                When you shift gears, how do the revs drop? The Motronic system does not interface with the trans... Actually nothing interfaces with the trans, there is no way rpm's would drop when you put it in gear (as long as the clutch is depressed).
                85 325e m60b44 6 speed / 89 535i
                e30 restoration and V8 swap
                24 Hours of Lemons e30 build

                Comment

                • EA8
                  Grease Monkey
                  • Oct 2008
                  • 328

                  #9
                  Originally posted by JGood
                  When you shift gears, how do the revs drop? The Motronic system does not interface with the trans... Actually nothing interfaces with the trans, there is no way rpm's would drop when you put it in gear (as long as the clutch is depressed).
                  true ...

                  the drop in rpms from 1500 to the normal 700-800 comes right after pressing the gas pedal slightly, when in gear. I should have been a little more clear on that. sorry for the confusion.

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