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Thread: very rough idle

  1. #1
    Join Date
    Nov 2004
    Posts
    205

    Default very rough idle

    525i
    m20
    1990

    the idle is really really rough...

    it jumps from 1000 to 1500 rpm...

    when i drive it...

    u can really feel the idle jumping...

    the speed of the car varies as it jumps... but when im
    on the accelerator... maintaining 2000... its normal
    except that i feel that there is a lack of power.

    any help will be highly appreciated.

    thanks!

  2. #2
    Join Date
    Dec 2003
    Location
    Eastern Tennessee USi
    Posts
    14,788

    Default

    as usual I cant help but have a suggestion. Reboot the computer and get a code after error from the stomp test, rebooting first should zero out on the problem at hand, most other errors fix them selves unless its a vacume related deal.

    post results
    Last edited by 632 Regal; 04-18-2007 at 09:30 PM.
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  3. #3
    Join Date
    May 2004
    Location
    Japan
    Posts
    9,175

    Default

    He cannot make a stomp test, as far as I know pong does not live in USA, so no US spec. car.

  4. #4
    Join Date
    Nov 2004
    Posts
    205

    Default

    thanks so much...

    i think this is a us spec car (imported frm guam)...

    but for some reason i couldn't make the stomp test
    to work...

    talked to friends who know stuff about engines...
    all of us think there is a air intake leak somewhere...

    the problem is i couldnt find one...

    im fearing that the leak might be from the manifold or
    something that drastic...

    this afternoon... besides the super rough idle
    temp started to climb to the red zone.

    then driving it tonight... the temp was jsut a bit above the
    middle... pretty much normal...

    i dunno if the heat (37 deg C this afternoon) and traffic did contribute
    a big part of this... but this is the first time it has happened...
    ( the overheating and the rough idle)
    thanks

  5. #5
    Join Date
    Nov 2004
    Location
    Gateshead,UK
    Posts
    926

    Default

    It sounds like a vacuum leak to me too. Even a leaking rocker cover gasket will make the rpm buck. Is there any oil clogging the inlet pipes/ICV/AFM? Try removing all of the intake side of the engine, give it all a good clean up and re-assembling it with new gaskets, seals etc.

    HTH,

    Shaun M

  6. #6
    Join Date
    Nov 2004
    Posts
    205

    Default

    ok... did a part by part diagnosis...

    it seems that it is the idle regulating valve

    T-SHAPE IDLE REGULATING VALVE BOSCH / 3 POL 1 11/1988 13411433626

    i tried removing the plug under it... it was supposed to increase idle speed if i do that... but the thing is... nothing changed... removed the hose going to it... tried to control the air using my hand... idle turned out to be ok.

    so this is most probably the culprit.

    is there a proper way of testing it?

  7. #7
    Join Date
    May 2004
    Location
    Japan
    Posts
    9,175

    Default

    Pong,
    my car does not have an ICV, all is controlled by the EML, so I am not sure how to check. But it looks like it is sticking
    http://www.realoem.com/bmw/showparts...13&fg=15&hl=13
    Did you clean it already?
    Here some comments from Shayne
    http://www.bimmerboard.com/forums/posts/247714/
    http://www.bimmerboard.com/forums/posts/216810/

  8. #8
    Join Date
    Nov 2004
    Posts
    205

    Default

    i think i cleaned it thoroughly already...

    soaked it in wd40... a lot of dirt came out...

    the flap or whatever ur calling it freely moves...

    but the thing is... i think its supposed to be spring
    operated... but there is no tension...

    it just stays in the position that i push it to...

  9. #9
    Join Date
    May 2006
    Location
    Antwerp, Belgium
    Posts
    552

    Default

    Quote Originally Posted by pong
    i think i cleaned it thoroughly already...

    soaked it in wd40... a lot of dirt came out...

    the flap or whatever ur calling it freely moves...

    but the thing is... i think its supposed to be spring
    operated... but there is no tension...

    it just stays in the position that i push it to...
    When I cleaned mine that happened too. Don't think it's a problem though. Unless someone disagrees and I turn out to be driving around with a shot ICV
    2008 audi A3 1.9tdi
    (former 1991 520i LPG)

  10. #10
    Join Date
    Oct 2006
    Location
    Reading, UK
    Posts
    1,853

    Default

    Quote Originally Posted by Morgenster
    When I cleaned mine that happened too. Don't think it's a problem though. Unless someone disagrees and I turn out to be driving around with a shot ICV
    If I remember correctly, the ICV is an adjust device - IE it has a signal to open more or open less instead of being open x% and closing automatically when there's no signal from the ecu...

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