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  • Rough idle

    The recent outbreak of good weather in Scotland caused me to go out and buy a z3m roadster to complement the coupe. When you consider they are half the price of the coupe they are still a bargain.

    I have had it serviced plugs filters etc but it still has a "lumpy tickover". It is fine when cold, but when hot it gets rough. It is totally smooth when you raise revs to over 1k.

    It feels just as powerful as the coupe and engine is totally smooth otherwise. Vanos kicking in and revving freely.

    It has done 85k miles and is the s50

    Any ideas of what I should look at?

    As for how it compares to the coupe- I think it is a "softer" version. Slightly smoother and actually an easier drive.

    When I bought it the gearbox/clutch was distinctly Massey ferguson. Replacing the clutch hose with a reinforced flexi transformed it.

    Nice to have the option of the two, although I still have the Toyota mr2 mk1 in the background for when I want something that will out handle either of them.

  • #2
    Since buying mine I've had three lumpy idles. Both sets of solenoids have needed re-soldering in the VANOS and the idle control valve / oil separator vavle pipework not being as fresh as it once was didn't help either.

    If you've got no loss of power I'd suggest whipping the plenum off and checking the pipes.

    Good luck, after all my hard troubles mine idles beautifully now!

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    • #3
      I would agree with Max, there are loads of pipes under the plenum that are prone to perishing and I have found one or two but still beed to get my plenum off to check the rest.
      Aceman

      Arctic Silver Z3MR

      Rocking seats ? You need seat bushes click HERE
      ///M Badge Refurb available HERE

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      • #4
        I would check the plugs first !

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        • #5
          The vacuum pipes under the plenum is what was preventing mine from passing its MOT

          Build thread: https://www.z3mcoupe.com/forum/showthread.php?t=19347

          Comment


          • #6
            I will try pipes first

            Replaced all the plugs at the service.

            I will check pipe work as a first pass

            By the way, when I open the coupe doors the windows drop fractionally to let air pressure equalise. It doesn't on the roadster. Difference or fault?

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            • #7
              Roadsters don't drop the windows as there is no need with the soft top.
              Aceman

              Arctic Silver Z3MR

              Rocking seats ? You need seat bushes click HERE
              ///M Badge Refurb available HERE

              Comment


              • #8
                Yea the Roadster doors just butt up to the door seals, on the coupe they drop and go up when the window is closed to fit under the door seal as they are frameless doors (it's not an air pressure thing). Essentially the Roadster's seals are compromised as it's a frameless door AND the door just closes on to them so are more prone to leaks/wind noise.

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                • #9
                  Originally posted by langlands View Post
                  The recent outbreak of good weather in Scotland caused me to go out and buy a z3m roadster to complement the coupe. When you consider they are half the price of the coupe they are still a bargain.

                  I have had it serviced plugs filters etc but it still has a "lumpy tickover". It is fine when cold, but when hot it gets rough. It is totally smooth when you raise revs to over 1k.

                  It feels just as powerful as the coupe and engine is totally smooth otherwise. Vanos kicking in and revving freely.

                  It has done 85k miles and is the s50

                  Any ideas of what I should look at?

                  As for how it compares to the coupe- I think it is a "softer" version. Slightly smoother and actually an easier drive.

                  When I bought it the gearbox/clutch was distinctly Massey ferguson. Replacing the clutch hose with a reinforced flexi transformed it.

                  Nice to have the option of the two, although I still have the Toyota mr2 mk1 in the background for when I want something that will out handle either of them.

                  Is it the same with/without your air con on?

                  Its still early days with me and my coupe (learning what's right and wrong), but noticed my idle was up and down while out for a drive while stopped at lights etc

                  It would go up to about 1300 rpm then drop to about 600 (which I think is about normal for idle) then back up to 1300, then repeat.

                  Turned the A/C off (as it does very little - another job to fix) and the idle yo-yo'ing stopped and went back to normal.

                  Not sure if this normal or not or even the same problem you've experienced. Just throwing it out there...

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                  • #10
                    Idle with aircon does raise very slightly but stays rock steady - should not swing to 1300rpm and down to 600rpm. Sounds like a problem with your idle control valve.

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                    • #11
                      I had the same problem with the variable idle - up to 1300, back down to 500/600, then repeat. From memory, is was something that just needed cleaning - maybe the throttle cable, or something through which it passes. It was a while back, so apologies for the lack of certainty.

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                      • #12
                        That'll be the idle control valve

                        Build thread: https://www.z3mcoupe.com/forum/showthread.php?t=19347

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