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Uneven Idle with aircon switched on

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  • Uneven Idle with aircon switched on

    I picked up my S50 last Saturday and on the way back I switched the aircon on as we actually had some sun. This caused the engine to bounce between 600 -1200 rev when idling. If I switched off the aircon it went back to normal.

    I test drove a couple of other S50's and one of them was on a hot day and it did exactly the same. Is this common or normal? Mine has a brand new Vanos so I know it's not that.

    I love the car and have been waiting a year to buy one.
    Ex 2000 S50 - Oxford Green II

  • #2
    If anything there should be a slight increase in idle speed when the aircon is switched on, you can also feel it when driving at low speeds; when you switch it on it feels on mine that it seems to drive itself at low speeds if that makes sense. As though there is extra throttle automatically added, probably via the idle control valve.

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    • #3
      I don't know how the aircon pump is activated, but if it's an electronic/magnetic clutch on the aircon pulley, could this or the aircon belt be slipping?

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      • #4
        Dirty or faulty idle control valve

        hi mate,

        congrats on the new car!!!

        I had the same issue just over a year ago due to the idle control valve being too dirty... the control valve is located under those 6 intake trumpets and you can pull it out and clean the unit up a bit with some WD-40.... I actually bought a clean used one and swap it straight in (just in case my was broken, and also I have a spare one)... the idle has been steady ever since with/without the A/C

        hope it helps!

        cheers,

        richie
        M Coupe from Australia

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        • #5
          Thank you all for your prompt replies. it sounds like a simple solution. I will investigate the idle control valve

          Thanks Glyn
          Ex 2000 S50 - Oxford Green II

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          • #6
            Originally posted by c_w View Post
            If anything there should be a slight increase in idle speed when the aircon is switched on, you can also feel it when driving at low speeds; when you switch it on it feels on mine that it seems to drive itself at low speeds if that makes sense. As though there is extra throttle automatically added, probably via the idle control valve.
            I turned the AC on yesterday for pretty much the first time and was surprised when in traffic the car seemed more lively without any right foot. Exactly as you described.

            Jez
            1998 Cosmos Black - Not quite standard ...

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            • #7
              Originally posted by glynmar View Post
              Thank you all for your prompt replies. it sounds like a simple solution. I will investigate the idle control valve

              Thanks Glyn
              Did this cure it? I ask, as mine is now doing *EXACTLY* the same. 600-1,200 with aircon on. 800 with aircon off.

              If you've cured it, I'm going to come back and ask (with my stupid hat on) *EXACTLY* which piece I need to clean. With pictures or something (looks sheepish).

              Jez
              1998 Cosmos Black - Not quite standard ...

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              • #8
                Originally posted by wadh0070 View Post
                Did this cure it? I ask, as mine is now doing *EXACTLY* the same. 600-1,200 with aircon on. 800 with aircon off.

                If you've cured it, I'm going to come back and ask (with my stupid hat on) *EXACTLY* which piece I need to clean. With pictures or something (looks sheepish).

                Jez
                If you end up looking for the ICV I posted a few pictures in this thread about where it is.

                http://www.z3mcoupe.com/forum/showthread.php?t=5116

                It's a bit of a bitch to get to but if you have small hands and a gymnasts flexibility then you should be fine ;)

                Comment


                • #9
                  Another pic:

                  http://www.z3mcoupe.com/forum/showth...?t=4254&page=4

                  Out: 99 S50 Titan Silver V876 KKO
                  In: 98 S50 Estoril.......

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                  • #10
                    Sorry for the delay in posting a reply. The problem was sorted out today. Turned out to be the AIRCON needed regassing. As on my car a dye can be put in the system so that if you use a ultra violet light it will show up any leaks on the system.

                    Ex 2000 S50 - Oxford Green II

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                    • #11
                      Update: went out in the coupe today one week on from the regas and aircon not working at all now. This time it's not affecting the idle speed. I guess there may be a leak in the system. Phew! that was hot today.
                      Ex 2000 S50 - Oxford Green II

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                      • #12
                        Did they put dye in when they regassed it. They should have, and that will tell where the leak is (if there is one).

                        Scuse any speeling mistakes. Few ales and all that

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                        • #13
                          I don't know whether or not a dye was added. Munich Legends recharged it last week but I am not sure if it is really covered by their warranty on the car, as they said it would only cover the engine and drivetrain. It is also a 3 hour round trip for me to keep going back to them.

                          Do you guys think I would be better off going to a aircon specialist rather than the BMW dealer/independant route?

                          Any suggestions who to go to in the Reading area rather than Cooper Reading at something like £135 an hour would be helpful?

                          Thanks

                          Glyn
                          Ex 2000 S50 - Oxford Green II

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                          • #14
                            If it worked after the regas then stopped working then I'm 99% sure it'll need a new condensor (which is the "radiator" at the front of the car) as they can get hit by small stones etc.

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                            • #15
                              Originally posted by c_w View Post
                              If it worked after the regas then stopped working then I'm 99% sure it'll need a new condensor (which is the "radiator" at the front of the car) as they can get hit by small stones etc.
                              It could also be a fucked compressor as well but more likely the condensor.

                              If you are in Berkshire, try K&M Autotechnik in Maidenhead, tell them Rags with the Red MC sent ya.

                              These guys are really helpful.

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