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Thread: Idle speed adjustment - solved

  1. #1
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    Idle speed adjustment - solved

    I've made some progress with my newly acquired 88 735i, manual transmission.... now I am ready to tackle another issue: My car idles high at about 1100 RPM. The idling is constant, not surging or oscillating ( engine hot). How do I adjust idling?
    Thank you,
    Jean
    Last edited by jeanro; 07-18-2018 at 08:15 PM.

  2. #2
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    here is some info for testing some parts https://www.bimmerforums.com/forum/s...-set-correctly
    Paul also has some good info on engine sensors http://paulaxford.com/html/bmw730i/index.htm
    already cleaned the Idle Control Valve (ICV) ?
    Check all vacuum hoses
    check temperature sensors
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
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    Also make sure that the throttle position switch (TPS) is correctly adjusted:
    a) between pins 2 and 18 of the TPS you must have continuity when the throttle butterfly is closed, and infinite Ohm when the throttle is partially open. You should hear a "click" and the resistance should chance from 0 to infinite as soon as the throttle turns just a little bit from fully closed position. If this doesn't happen, then adjust the TPS by loosening the screws and turning the TPS a little bit. Then test again.
    b) between pins 3 and 18 of the TPS you must have continuity when the throttle is fully open (actually it's continuity on a range from almost fully open to fully open), and infinite resistance with the throttle is in any other position.
    If, no matter how much you try adjusting, you cannot find a position of the TPS where both conditions "a" and "b" above are met, then most likely your TPS is defective.

    If pins 2 and 18 don't have continuity when the throttle is fully closed, then the engine may idle high.
    --
    1994 E32 730i M30 manual
    ex- 2006 E86 Z4M Coupe
    ex- 1986 E28 535i

  4. #4
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    So you don't have to hunt around for the vacuum hose diagram. Look here. Remember, one vacuum hose comes off of the top of the fuel regulator and the other comes off of a little T connection coming out of the boot. Both go to the bottom of the intake manifold. Check the picture. I would replace them anyway since if they're original they could be leaking somewhere along the line. Very inexpensive.







    Also check hose from Idle control Valve to intake manifold. If it's not solid and or leaking it can make a mess of your idle.

    Last edited by CroughtonE32; 07-17-2018 at 04:24 PM.
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
    https://www.youtube.com/watch?v=2d4tHoHGaJo
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  5. #5
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    Guys,
    Thanks a lot for all the info : I'll get busy now...
    Tha car sat for about 18 yrs now, and is very probable that some vacuum lines are toast.Shogun, I did not check the ICV valve, nor any other hoses.I'll report back...
    Thanks again

  6. #6
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    Just in case you're not sure.......this is the idle control valve. Good luck.
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
    https://www.youtube.com/watch?v=2d4tHoHGaJo
    https://1drv.ms/v/s!Av20xCMMocSsyEpl...h_oOk?e=ekIcAT







  7. #7
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    Ok, I am back with some test results: Car started at 1100 RPM and kept running at same the value disregarding engine temperature. I pulled the ICV and cleaned it : sprayed some AFM fluid inside, shook it well and reinstalled it....nothing different after starting the engine as it ran at the same 1100 RPM. Pulled the ICV connector while running and I've got no response, nor when I plugged it back in...I pulled the TPM sensor connector with the engine running, and the motor started revving up. Pulled the oil dipstick, and the RPMs dropped to 1000. All the vacuum hoses seem OK.
    Is there a way to test the ICV valve ? Is it normal to have no RPM reaction with it out of the circuit? As a matter of fact, one time the engine almost stalled when I plugged the connector back in, after that....nothing.
    I will go ahead and do the resistivity test for the TPM as Robert is suggesting....
    Any ideas?

  8. #8
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    Quote Originally Posted by jeanro View Post
    I will go ahead and do the resistivity test for the TPM as Robert is suggesting....
    Yes, it is still worth testing the TPS, in order to make sure that it is all right. However, based on your report above, I expect it to check out OK. You said that you unplugged the TPS connector while the engine was running, and immediately the engine revved up. That behavior suggests the TPS may be OK.

    Another easy thing worth checking is the throttle butterfly position. When the throttle is fully closed, the gap between the throttle butterfly and housing should be about 0 (meaning, in real life, not larger than 0.03mm).
    Use a feeler gauge (0.02mm or 0.03mm), insert it between the butterfly and the housing when the butterfly is partially open (otherwise you may break the gauge), the let the butterfly close gently, and check the gap. If you cannot move the feeler gauge, or you can move it with some drag, then most likely the throttle butterfly is correctly set. On the other hand, if the feeler gauge moves with very little drag or no drag at all, then you must adjust the butterfly.
    There's an adjustment screw on the throttle housing.

    Notes:
    1. If you don't have such a thin feeler gauge, then just set the throttle to zero gap (= no tension on the adjustment screw), and test the idle. Then re-set the adjustment screw in order to have some tension on it, so that the butterfly barely pushes on the adjustment screw instead of on the housing, in the fully closed position.
    2. Use this occasion to clean the inside of throttle body and the throttle butterfly, including the edges of the butterfly. A lint free rag soaked with some carburetor cleaner or gasoline would do.
    Last edited by RobertRO; 07-18-2018 at 05:22 AM.
    --
    1994 E32 730i M30 manual
    ex- 2006 E86 Z4M Coupe
    ex- 1986 E28 535i

  9. #9
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    Well, You guys are awesome!!!
    Robert, I did have to adjust the TPM a bit, but it did not make a big difference untill I have discovered that my ICV valve was actually stuck. Last night, after my first unsuccesful attempt to lower the RPM at idle, I went on line and I wached a video with a guy testing the ICV valve by rotating it fast along the long axle, left and right about 90 degrees each direction : the ICV valve was actually clicking which led me to the conclusion that the valve is actually mechanically closing and opening function of "something". Anyway, back to the garage, took the valve off, shook it....nothing. Pulled the best mechanic from the shelf (WD-40) sprayed it good, let it sit for 10 min, shook it again, and it clicked!!. Installed it in the car, and... VICTORY!! The car idles steady at about 700-750 RPM with a hot engine.
    Thank you guys!!!

  10. #10
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  11. #11
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    Shogun tricks and tips for the E32 series are HERE!

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