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Thread: Oscillating Idle and Cold Start - 1983 635CSI Euro

  1. #1
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    M5,328i,3.0csi,635csi

    Oscillating Idle and Cold Start - 1983 635CSI Euro

    Hello guys,

    Have had bimmers for quite some time but new to e24s and the M30.

    I've searched the forum for likely answers but can't be sure so I would like to ask:

    My M30 has a constant oscillating idle per the video below. ICV seems to be fine and there doesn't seem to be any leaks from the vacuum hoses, according to my mechanic. I'm thinking it's either AFM or injectors. Does anything else come to mind or has anyone had similar issues?

    https://m.youtube.com/watch?v=8Ewi0HuwmlY

    Another thing is cold starting. The engine will crank and turn on but can't maintain idle. It'll stall if I don't help with the gas pedal: both on cranking and when the engine is on, for the first 40 seconds, until it is warm enough to maintain idle. I've read about the cold start valve and temperature sensor being the culprit but it seems like they only work during key turn, right?

    https://m.youtube.com/watch?v=T0ATygHeC2g

    Appreciate any advice.
    thanks!

  2. #2
    Join Date
    Jul 2009
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    St. Louis, MO
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    '84 635 Euro/'14 328i GT
    Have you checked your Aux Air Slide Valve [part #13631284414]? Late '82-'84 Euros have this part, some discussion towards the end of this old thread here: https://www.bimmerforums.com/forum/s...ir+slide+valve

    More visuals in this thread (the '80-'81 E12 part is the same as in our cars): http://www.firstfives.org/faq/aux_ai...air_valve.html

    This fixed my issue when I was having similar symptoms. I'm a little confused when you say ICV seems to be fine as this generation of Euro doesn't technically have one (they arrived in '85).

  3. #3
    Join Date
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    Hi Lapis,
    Thanks for your reply. I'll look into buiyng the air slide valve, if I can find it within the online stores. Given it's for a Euro motor, none of the traditional stores in the US carry it (Pelican, FCP, Turner, etc.)

    When I mention "idle control valve", I'm referring to part #13411286065.

    While I'm at it, might as well look into a new cold start valve and temperature switch, I guess.

    THanks again,
    Best,
    Pedro

  4. #4
    Join Date
    Dec 2007
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    6/83 1984 745i
    The cold start is a huge whore to change JFYI. Maximillian should be able to order the slide valve.
    alpinweiß on anthrazit buffalo 1984 745i, 2014 Fiesta ST, 1984 635csi 1986 635csi 1987 L6 1999 M coupe 2002 M3 1995 325i 1976 200​2, 2001 996 TT 1994 850 T5 wagon 1998 GTi VR6 1983 scirocco

  5. #5
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    Hi Freshbread,
    Thanks for the info. Sorry but who is Maximillian? a member of the group here?

    Also, if you or any of the viewers have any comments on the oscillating idle issue, per my original post, I'm all ears!!!
    Best,
    Pedro

  6. #6
    Join Date
    May 2009
    Location
    Camas, WA
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    1,167
    My Cars
    Euro '85 635csi
    Maximillian is a website that you can puchase from. They can get a lot of euro parts. I've ordered from them before.

  7. #7
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    EXOTICS
    Classic intake leak symptoms.
    By that age, rubber intake boots and all vacuum hoses have deteriorated, if they've never been replaced.
    Remove and carefully inspect all rubber boots and miscellaneous engine vacuum hoses,
    Replace all with any sign of cracks.
    Also, remove and inspect all tune-up parts:
    Sparkplugs & gap, along with wires
    Distributor cap, especially inside contacts condition

  8. #8
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    Got it.
    Thanks dmac156 and Mikyzzz4!

  9. #9
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    EXOTICS
    Report back with your results.

  10. #10
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    Been a while but better late than never, also for future reference for those with similar problems. Air slide valve was the culprit. Thanks again for all the help given.

  11. #11
    Join Date
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    '84 635 Euro/'14 328i GT
    Quote Originally Posted by parlant View Post
    Been a while but better late than never, also for future reference for those with similar problems. Air slide valve was the culprit. Thanks again for all the help given.
    Good to hear, this definitely cured my issue a few years ago and there isn't much written about it because it only applies to such a narrow window of Euro models.

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