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  • low idle and stalls

    Have just serviced and fitted a new fan on the coupe and decided to take it for a good run. Goes like a Stabbed rat :) sounds like a proper M car at the higher end of the rev range.

    However the new problem is when pulling up at junctions it wants to idle around 5-600 rpm and then might slightly raise to more like 800 or just drop and stall, or it might bounce upto 1200 and slowly drop to 800.

    It seems worse from a warm start, if I drive it from cold and dont trun it off it seems ok, or better. Once you do turn it off, at maybe a petrol station, it will probably want to cut out as you leave and maybe again at the next junction.

    I was thinking about checking under the plenum for air leaks. Checking for the "t" piece bung, and maybe try and get to the ICV, and give that a clean. I was going to do this myself, do I need any specific tools to remove the Plenum? There doesnt seem to be much on line for the Euro spec s50.

    Do the symptoms above sound like ICV or air leak as sometimes it idles ok? was thinking it could be Throttle position sensor. I havnt been able to access the codes on the car as my indie carnt get into the dme to read them, he managed to delete them but they came back straight away.

    I guess I realise the idle problems could be from numerous issues and wondering if you guys had any views on where to start? Thanks Dave

  • #2
    Removing the plenum(airbox) only requires basic tools, not sure if you can get to the bung with it in place but if you want to clean the icv then it will need to be removed. There's loads of info on the forum regarding idle issues but without codes it will be a case of elimination. Worth also checking condition of throttle cable and also oiling and checking return of throttle bodies which can give high rpm at idle, but S50B32 engines when running correctly should idle low so 600/700 isn't a problem if it doesn't stall. Where are you in the Country?

    idle tags,

    https://www.z3mcoupe.com/forum/tags.php?tag=idle

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    • #3
      Idle

      Hi Dave, thanks for that, I guess it's a matter of elimination, I,m in Nottingham, I believe you can see if there is a bung on the T piece by removing the air box, as per a post I read on here.

      I think you are right, in terms of get the codes read, could be something like a cam sensor, but not sure if these even have them! Could be vanos solenoids but the codes might point to something.

      I might take airbox off and see if there is a bung on T piece as this should be a start to explore the mysteries of the right side of the engine and all those old bits of rubber pipes :0

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      • #4
        The plenum is a bit of a pain to remove but I have done it a few times and I am no mechanic, I removed the air filter housing assembly and the chrome nuts on the air intakes, remove bracket with throttle cable, the worst part is removing the nuts from the bottom bracket of the plenum and the two? hose clips on the base of the plenum. Not a guide as cant remember all the stages but the main problem is access as its pretty tight getting your hand or hands around the base of the plenum. With the plenum removed you can get a good look at the many rubber hoses some of which have be known to break down over time and removal of the idle control valve.

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        • #5
          Plenum removed showing Y shaped bracket,

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          • #6
            There are three? hoses that need to be removed, one on top off plenum and two below, also a electrical connector on bottom of plenum



            Last edited by Dave P; 01-10-2019, 10:18 AM.

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            • #7
              Thanks Dave

              Hi Dave, thanks for that, I will have a look, if my engine bay looks anything like as clean as yours I will be very shocked, it looks brand new! The photos will help me to work out what is what, so thank you. Thanks again, Dave

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              • #8
                Here's a picture showing the underneath of the plenum, (one of the mounts is missing from the left side)

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                • #9
                  Yes the two 13mm nuts can be tricky to undo (and refasten) but can be done. I also find that undoing the smaller vac hose (the one that goes down to a y-piece) is easier to detached at the bottom and leave it attached to the manifold.

                  Other tricky one is the horiztonal pipe (around 30mm diameter) that sits at the top in centre.

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                  • #10
                    Thanks

                    Thanks for advice, was also going to ask what would you guys recommend for giving things a bit of a clean, am not going to compete with Daves engine bay, but just a good wipe.. I believe carb cleaner for the ICV, not sure what to use to clean the inlet butterflys or the other hoses and mechanical s I will uncover, any suggestions. Was thinking WD40? Thanks, Dave

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                    • #11
                      I use Meguiars all purpose cleaner for the oily jobs (Halfords sell it) but I would think the carb cleaner on a clean cloth would work on the inlets and butterflies. Never tried wd40 so would be interested in the results.

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