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Thread: m20 spark plug gap

  1. #1
    Join Date
    Nov 2004
    Posts
    205

    Default m20 spark plug gap

    what gap do u guys use?

    im reading and it says .28 to .32
    however, when im at .29... the engine idles rough and dies once in while
    while idling and on drive
    im trying it at .30 now... so far its better but its still kinda rough... died only
    once while in traffic and on drive ( didnt bother trying it again)
    will opening it up to .31 or .32 be better?

    thanks!
    (m20 525i)

  2. #2
    Join Date
    Jan 2007
    Location
    San Jose, CA
    Posts
    267

    Default

    I use .28, but have tried up to .32! Pretty safe to say that your idling problems are not caused by that tiny difference in gap; you have some other problem such as a vacuum leak.

  3. #3
    Join Date
    Nov 2004
    Posts
    205

    Default

    with the term idling rough... it is at 500rpm with aircon and gear...
    without the gear, its at 750 and its ok.
    without the aircon, at 800-850 and idle is good

    with the old gap... the plugs seem to be burnt when i removed them

    with the change in the gap for me... the engine does not die a lot often...

  4. #4
    Join Date
    Feb 2008
    Posts
    370

    Default

    Quote Originally Posted by pong
    what gap do u guys use?
    i'm really interested to hear what the wise-men do here...

    i only stalled once - was having alternator troubles and i still think it was something to do with that.

    but i have the same funny idle only when it's in a (auto)gear not park or N.

    i have changed the plugs twice since i bought it last summer - they were toast then and when i changed them again in december they were getting pretty toasted already - probably something to do with my many disasters or because fuel-system cleaners were used on it for the first time in 20 years -but i'm pretty sure they are gapped at .28 and if that can cause problems i'd like to change it.

  5. #5
    Join Date
    Jan 2007
    Location
    San Jose, CA
    Posts
    267

    Default

    That tiny difference in gap should not make that sort of difference. I would open it up to .32 and see if it runs okay. If it does, your coil is probably fine. If it runs fine at .32 and .28, but didn't at something in-between, it was just coincidence.

    When was the last time you changed your plugs, wired and rotor?

    Also, a slight brown color to the plugs is normal burn.

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