Sputtering off idle

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  • Zreberlcoe
    E30 Mastermind
    • Jan 2012
    • 1555

    #1

    Sputtering off idle

    Okay so when the car is at Idle and you flick the accelerator the motor drops in RPM before it goes up. I was thinking it was the TPS, but I checked the Ohms and it seems to be fine. I have been searching for a vacuum leak but I haven't had any luck! I checked the intake L boot, the ICV, and other vacuum lines. Also when you pull through second gear, throttle fully open, from about 4000-5500 RPM the motor seems to lag and pick back up again just slightly.

    Here's a video:
    https://flic.kr/p/nGjHkA
    1991 325i Calypso Coupe

    Like Grandfather, Like Father, Like Son
    BMW

  • jlevie
    R3V OG
    • Nov 2006
    • 13530

    #2
    The only way to find intake leaks is to have a shop run a smoke test. Other things are possible, but rule out intake leaks first.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

    Comment

    • Zreberlcoe
      E30 Mastermind
      • Jan 2012
      • 1555

      #3
      Originally posted by jlevie
      The only way to find intake leaks is to have a shop run a smoke test. Other things are possible, but rule out intake leaks first.

      Is there a smoke test I can do at home?
      1991 325i Calypso Coupe

      Like Grandfather, Like Father, Like Son
      BMW

      Comment

      • dnguyen1963
        R3VLimited
        • Nov 2011
        • 2648

        #4
        yes, there are lots of DIYs out there. Google is your friend. You have to remember to keep the pressure between 2-4 psi by plugging both intake and exhaust to find all the leaks.

        Comment

        • jlevie
          R3V OG
          • Nov 2006
          • 13530

          #5
          Originally posted by dnguyen1963
          yes, there are lots of DIYs out there. Google is your friend. You have to remember to keep the pressure between 2-4 psi by plugging both intake and exhaust to find all the leaks.
          And you must use oil smoke.
          The car makes it possible, but the driver makes it happen.
          Jim Levie, Huntsville, AL

          Comment

          • b1mm3r
            Advanced Member
            • Apr 2014
            • 184

            #6
            Try running some seafoam also. Could be fuel related, have you checked fuel pressure? What about spark plugs, checked those?
            sigpic
            87 325e DD--93 318is s50--07 3.0 X5 wifes

            Comment

            • Zreberlcoe
              E30 Mastermind
              • Jan 2012
              • 1555

              #7
              I replaced spark plugs with Bosch super plus. Replaced air filter. I don't know about fuel pressure or the last time the fuel filter was done. I just sprayed all the intake anything and vacuum lines with a full can of carb cleaner and found no change in idle. And I unplugged my ICV for a couple of seconds and plugged it back in and nothing changed, is that bad?
              1991 325i Calypso Coupe

              Like Grandfather, Like Father, Like Son
              BMW

              Comment

              • mpowerful
                E30 Fanatic
                • Jul 2013
                • 1273

                #8
                Your car shouldnt run at idle with iacv unplugged. Perhaps iacv is stuck open.

                Comment

                • Zreberlcoe
                  E30 Mastermind
                  • Jan 2012
                  • 1555

                  #9
                  Originally posted by mpowerful
                  Your car shouldnt run at idle with iacv unplugged. Perhaps iacv is stuck open.

                  Suggest replacement?
                  1991 325i Calypso Coupe

                  Like Grandfather, Like Father, Like Son
                  BMW

                  Comment

                  • jlevie
                    R3V OG
                    • Nov 2006
                    • 13530

                    #10
                    Originally posted by mpowerful
                    Your car shouldnt run at idle with iacv unplugged. Perhaps iacv is stuck open.
                    Actually it will and should idle at a slightly higher speed.
                    The car makes it possible, but the driver makes it happen.
                    Jim Levie, Huntsville, AL

                    Comment

                    • E30Gus
                      Mod Crazy
                      • Jun 2008
                      • 781

                      #11
                      Mine does this off throttle and have narrowed it down to the AFM trace degradation. You can swap with a known good AFM and see if it goes away.

                      Comment

                      • pandaiswong
                        Advanced Member
                        • Apr 2014
                        • 112

                        #12
                        Maybe your AFM just needs adjustment?
                        1992 Daihatsu Rocky SE
                        1988 BMW 325 SETA

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