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  • Throttle Cable or Coils or MAF?

    Been looking round the forum for an idea on this one.

    Has anyone else experienced what I can only describe missing, surging or grabbing (in other words it is hard to describe) when at high speed, motorway driving, then a little lift off, power on again?

    There is the sensation of a pause or a really slight surge when you lift off followed by a grabbing feel.

    Tried different fuels (this was all on the continent so Texaco 98 and Shell v power), same effect - full tank.

    Recent oil change (Friday!) and diff has been rebuilt recently so power delivery is smooth. Pads are not sticking either.

    Feel is through the pedal and only for a split second before normal service is resumed.

    Any ideas?

  • #2
    sounds like a misfire to me, which could be anything......injectors, plugs, ignition, various sensors in the fuel system (MAF included), vacuum leak

    maybe the Z3m is new enough to tell you something in the codes ?

    if not I can only suggest plodding through it starting with the cheaper / simpler tests ......

    Comment


    • #3
      Originally posted by Bruski_11 View Post
      Been looking round the forum for an idea on this one.

      Has anyone else experienced what I can only describe missing, surging or grabbing (in other words it is hard to describe) when at high speed, motorway driving, then a little lift off, power on again?

      There is the sensation of a pause or a really slight surge when you lift off followed by a grabbing feel.

      Tried different fuels (this was all on the continent so Texaco 98 and Shell v power), same effect - full tank.

      Recent oil change (Friday!) and diff has been rebuilt recently so power delivery is smooth. Pads are not sticking either.

      Feel is through the pedal and only for a split second before normal service is resumed.

      Any ideas?

      don't think it would be cable related

      Comment


      • #4
        Thanks guys, diagnostic sounds like a good start. Cable was a bit much to hope for. Misfire is as good a description as anything.

        Comment


        • #5
          Originally posted by Bruski_11 View Post
          Thanks guys, diagnostic sounds like a good start. Cable was a bit much to hope for. Misfire is as good a description as anything.
          Had a similar issue with my coupe. I cleaned the maf sensor with electrical contact cleaner and it cured the problem. Be careful if you attempt to do this as the maf is delicate and is easily broken.

          Comment


          • #6
            Originally posted by David z coupe View Post
            Had a similar issue with my coupe. I cleaned the maf sensor with electrical contact cleaner and it cured the problem. Be careful if you attempt to do this as the maf is delicate and is easily broken.
            There's a tutorial on YouTube with a guy doing it on a e36 from memory

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            • #7
              thanks guys

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              • #8
                I am sure I have a similar mis-fire? but replaced MAF with new and its still happens albeit very occasionally

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                • #9
                  misfire

                  had similar problem with my car had random misfire
                  I removed spark plugs to check all were firing noticed no 5 second from bulkhead had unburned fuel at tip. I replaced all spark plugs but problem still continued.I then replaced ignition coil on no5 cylinder 95% cure still had very slight misfire finally traced it to the large concertina hose between the maf sensor and the engine the hose had degraded underneath and was starting to split.This could only be seen with the removal of the hose .
                  No more misfire
                  hope this helps
                  regards
                  alan

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                  • #10
                    I would in this order.

                    Clean the MAF with an electrical cleaner fluid. Halfords will have the one.
                    Clean throttle body
                    Check breather hoses.
                    Try a fuel cleaner
                    Use diagnostic machine
                    Change spark plugs
                    Change one coil pack, and keep swapping over to see if it resolves.

                    Comment


                    • #11
                      I would personally avoid touching the MAF sensor as a last resort, only because they are very sensitive (but also very reliable) and trying to clean them can sometimes cause more problems than you are trying to solve. If the car's always had a decent air filter in, it shouldn't ever get dirty.

                      Ensure the throttle cable is free as it may just have a slight grab from the cable when releaseing. Also check the throttle bodies and return springs are snapping back nicely to rest positon.

                      The throttle switch/potentiometer can wear and on my car it caused a feeling of misfire at cruise part throttle as that is where it wears the most. Really easy to swap as it sits at the end of throttle rail.

                      Other than that could it be a vanos issue?

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                      • #12
                        I think I had this same issue and did as Chris says and changed the TPS. My memory is a bit hazy as I had a couple of others things done around the same time but pretty sure I remember changing it myself, only 1 plug and 2 bolts if I remember correctly.

                        Symptoms were that the car was fine everywhere apart from when sitting at motorway speeds where it would seem to misfire. Going 10-15mph faster or slower seemed to cure it (but not very practical) which makes sense as pointed out in the post above.

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                        • #13
                          It is an odd one, power is smooth but then, as others have described, only on slight lift off, does the "misfire" occur. I think I need to take it for a motorway drive and see if I can recreate consistently.

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                          • #14
                            As c_w has said, I wouldn't advise cleaning the MAF with an electrical cleaner, best left alone.
                            I'm not sure of the cost to replace the MAF on an M Coupe but I recently used this company for another car to refurbish the AFM as replacement new cost was £1,200.00 vs a few hundred to refurb:
                            https://www.atpelectronics.co.uk/

                            That's of course if you think it is linked to the MAF...

                            Comment


                            • #15
                              Really easy to clean MAF as long as you are careful , I replaced MAF and throttle switch with new and still have a similar problem with no fault codes. I think mine is coil related so will try swapping these for new and seeing if that cures it.

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