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Revving the M42 to it's redline, then boom stuttering/sputtering

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    Revving the M42 to it's redline, then boom stuttering/sputtering

    My M42 seems to be pretty healthy, but when I get too close to redline/actually at redline to shift, the car doesn't hit it's rev limiter, it instead begins to sputter and have basically no power until I put the clutch in and wait for it to idle. It's fine after that, but does anyone know why this is happening?
    91 318iS - aluminum M52B28 + ZF320 + 3.15 Torsen

    #2
    Could be anything, but i would start by inspecting the spark plugs and the fuel filter (replace both if you dont know the history)

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      #3
      Originally posted by e30davie View Post
      Could be anything, but i would start by inspecting the spark plugs and the fuel filter (replace both if you dont know the history)
      I suppose I should have put this in the original post, but spark plugs have been changed recently, along with coils and wires. Fuel filter has been changed as well.

      Could it be something to do with the engine ground or a camshaft sensor?
      91 318iS - aluminum M52B28 + ZF320 + 3.15 Torsen

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        #4
        What RPM exactly, and is it very consistent or intermittent?

        Comment


          #5
          crank sensor maybe
          89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

          new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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            #6
            Check this vid, are these symptoms similar to yours? If so, it's crankshaft position sensor.

            https://www.youtube.com/watch?v=bPNIZQ5kn3w
            My 1991 318is Progression Thread

            Comment


              #7
              Originally posted by bmwman91 View Post
              What RPM exactly, and is it very consistent or intermittent?
              It happens right before redline, although sometimes it will let me hit redline and it won't bounce, instead it'll just retard the revving and start stuttering/sputtering. So probably around 6500-7000 every single time.

              Originally posted by digger View Post
              crank sensor maybe
              That's highly possible as I had a problem with it before...
              91 318iS - aluminum M52B28 + ZF320 + 3.15 Torsen

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                #8
                Yeah, crank sensor, or maybe an ignition coil on its way out. Also if the fuel filter is plugged up you might be dealing with intermittent fuel starvation at higher flows.

                Pull the spark plugs and check to see if any of them look odd, either sooted/rich or white/lean.

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                  #9
                  Check fuel pressure first.

                  Then, in addition to what everyone else said, make sure the AFM tests OK.

                  t
                  now, sometimes I just mess with people. It's more entertaining that way. george graves

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                    #10
                    Originally posted by TobyB View Post
                    Check fuel pressure first.

                    Then, in addition to what everyone else said, make sure the AFM tests OK.

                    t
                    You mean to tell me that this OP shouldn't convert to dual side drafts?

                    Comment


                      #11
                      Originally posted by TobyB View Post
                      make sure the AFM tests OK.
                      Is the AFM referenced during WOT?

                      Comment


                        #12
                        Originally posted by Victell View Post
                        Is the AFM referenced during WOT?

                        Yes, it is still used as the primary input for calculating a base load value. The O2 sensor is ignored.

                        Comment


                          #13
                          Revving the M42 to it's redline, then boom stuttering/sputtering

                          CPS most likely. Had to replace mine 2x, once with aftermarket and finally with OEM. Hasn’t done it since. Exact same symptoms as the video. OEM was fuck-all expensive iirc.


                          Ezekiel 25:17
                          Current flame: E30 318iS Alpinweiss II slicktop / LSD - Joanne
                          The old man: 1970 2002 Polaris(ish) slicktop / rat rod - Wallace
                          The ex: E92 335i 6MT M-Sport - Betty
                          The heavy: 2001 4Runner SR5 Sport (3rd Gen) - Fred

                          Comment


                            #14
                            majmodo I agree 100% on that.. I also got the Bosch part first and my car was no-start whatsoever after that. Once I got the OEM it was 100% back to normal. Unfortunately it has jumped in price, but if you want good reliable performance from your car it's necessary. Worth it for these great old cars.

                            CPS on ecs 19Mar2019: $232
                            https://www.ecstuning.com/b-genuine-...r/12141721504/
                            Last edited by Nairb; 03-19-2019, 08:13 AM.
                            My 1991 318is Progression Thread

                            Comment


                              #15
                              Originally posted by Nairb View Post
                              majmodo I agree 100% on that.. I also got the Bosch part first and my car was no-start whatsoever after that. Once I got the OEM it was 100% back to normal. Unfortunately it has jumped in price, but if you want good reliable performance from your car it's necessary. Worth it for these great old cars.

                              CPS on ecs 19Mar2019: $232
                              https://www.ecstuning.com/b-genuine-...r/12141721504/


                              Right on - wish I’d done this repair myself, but ended up paying the mechanic to hunt down the problem. Almost paid him to replace a perfectly functioning cat, thought it was a blockage in the exhaust.


                              Ezekiel 25:17
                              Current flame: E30 318iS Alpinweiss II slicktop / LSD - Joanne
                              The old man: 1970 2002 Polaris(ish) slicktop / rat rod - Wallace
                              The ex: E92 335i 6MT M-Sport - Betty
                              The heavy: 2001 4Runner SR5 Sport (3rd Gen) - Fred

                              Comment

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