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Thread: Random miss at idle

  1. #1
    Join Date
    Jan 2004
    Location
    Lexington, Kentucky
    Posts
    2,561

    Default Random miss at idle

    I was idling the car (with air on ) for about 10 minutes today after a drive and noticed somthing new. every once in a while it seems to randomally miss/falter at idle. Never noticed it while driving. no miss noticible when it revs from idle. All maintainace is up to date. PLugs filters/oil etc.

    Anyone? TIA
    Thanks,

    1995 525i Auto, M50TU 2.5L, EAT chip, 1/95 build, USA, 205/65/15 tires, ASC+T, HID, lumbar, EC Mirror, BMW Alpine 5 radio with BMW-Pioneer CD Changer, abt 236k miles, Oxford Green/Parchment

  2. #2
    Join Date
    May 2004
    Location
    Japan
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    9,270

    Default

    Check the distributor cap and the rotor, even if the maintenance is up to date.
    Quickly done.

  3. #3
    Join Date
    Jan 2004
    Location
    NC
    Posts
    755

    Default M50tu uses coil-on-plug ignition

    Quote Originally Posted by shogun
    Check the distributor cap and the rotor, even if the maintenance is up to date.
    Quickly done.
    probably not that
    Bill B.
    95 525i


  4. #4
    Join Date
    Jan 2004
    Location
    NC
    Posts
    755

    Default You sure it's not when the compressor cycles off and on?

    Quote Originally Posted by Russell
    I was idling the car (with air on ) for about 10 minutes today after a drive and noticed somthing new. every once in a while it seems to randomally miss/falter at idle. Never noticed it while driving. no miss noticible when it revs from idle. All maintainace is up to date. PLugs filters/oil etc.

    Anyone? TIA
    My wife's does that too with the A/C on, when the clutch kicks in and the revs drop momentarily.
    Bill B.
    95 525i


  5. #5
    Join Date
    Nov 2004
    Location
    Winston-Salem, NC
    Posts
    603

    Default

    Quote Originally Posted by Russell
    I was idling the car (with air on ) for about 10 minutes today after a drive and noticed somthing new. every once in a while it seems to randomally miss/falter at idle. Never noticed it while driving. no miss noticible when it revs from idle. All maintainace is up to date. PLugs filters/oil etc.

    Anyone? TIA
    Russell,

    Shogun's on it but you don't have a cap. You have direct fire coils on top of the plugs. It sounds like one of those is going or gone. The tell-tale sign (I found out this weekend) is the presence of flaky brown residue, like dried out caramel on the end of the plug connector. That means the coil has fried the insulation and it's going way bad.
    New Bremi coils can be found from BMA Autoparts for around $45.
    -ashley


    '92 525iA / 179k miles / Born 3.92 / ABS / No ASC / stock / North Carolina



    Paper Gaskets Suck!

  6. #6
    Join Date
    Jan 2005
    Location
    Scotland
    Posts
    119

    Default

    Might also be oil down at the plug (from a slightly leaky gasket)...

  7. #7
    Join Date
    Jan 2004
    Location
    Lexington, Kentucky
    Posts
    2,561

    Default Bit of update

    New plugs about month ago. tiny bit of oil in bottom of wells. Valve cover gasket about 16 months old. I do question coils as I had two of them with a bit of "candy" on the top surfaces of the original Bremi coils. BTW, previous plugs all burned very clean.

    Do not believe a vacumn leak. Even so I replaced the charcoal canister about a month ago. Will check out in more detail this evening or this weekend.

    Do believe AC compressor kicking in as if "felt" different, not a drag but a cutout for a split second.
    Thanks,

    1995 525i Auto, M50TU 2.5L, EAT chip, 1/95 build, USA, 205/65/15 tires, ASC+T, HID, lumbar, EC Mirror, BMW Alpine 5 radio with BMW-Pioneer CD Changer, abt 236k miles, Oxford Green/Parchment

  8. #8
    Join Date
    Jan 2004
    Location
    Benneton (United Colors of)
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    3,067

    Default

    id bet money its the leaking valve cover gasket. having the "candy" doesn't help. take the coils off, and put a q-tip in the end of a set of needle nose pliers. remove the oil. clean the ends of the boot ends with the qtip until no residue remains. use some contact cleaner up in them if you have it and you think the boot would survive the solvent. pull the plugs and wipe the ceramic and top parts off. remember, the valve cover gasket sits pretty high up on the spark plug well. if its leaking oil, its spraying it pretty high up, which means a decent amount had to spray into there befoire it dried or dripped to the bottom, if there is an accumulation. im almost certain its that, and doing this costs nothing except your time.
    "..Torchinski v. Peterson that it is legal to carry a concealed weapon, so long the weapon is totally slick like a huge ass machine gun that you carry under a trench coat, like in the Matrix."


  9. #9
    Join Date
    Jan 2004
    Location
    Lexington, Kentucky
    Posts
    2,561

    Default Thanks-No miss this evening?

    Even though the temperature was 101 and the air was on in heavy traffic. I may just need to wait until it "gets broke enough to fix". I just may have had some bad gas. I added BP 93 the other day. I normally use either Chevron or V-Power 93. Will watch for a few days

    Quote Originally Posted by ryan roopnarine
    id bet money its the leaking valve cover gasket. having the "candy" doesn't help. take the coils off, and put a q-tip in the end of a set of needle nose pliers. remove the oil. clean the ends of the boot ends with the qtip until no residue remains. use some contact cleaner up in them if you have it and you think the boot would survive the solvent. pull the plugs and wipe the ceramic and top parts off. remember, the valve cover gasket sits pretty high up on the spark plug well. if its leaking oil, its spraying it pretty high up, which means a decent amount had to spray into there befoire it dried or dripped to the bottom, if there is an accumulation. im almost certain its that, and doing this costs nothing except your time.
    Thanks,

    1995 525i Auto, M50TU 2.5L, EAT chip, 1/95 build, USA, 205/65/15 tires, ASC+T, HID, lumbar, EC Mirror, BMW Alpine 5 radio with BMW-Pioneer CD Changer, abt 236k miles, Oxford Green/Parchment

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