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Thread: Misfire - not Coils or Plugs

  1. #1
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    Misfire - not Coils or Plugs

    I have a 2012 VW Golf GTI, and the past couple months it's been running rough, particularly when cold.

    My Ross-Tech cable shows it missing on cylinder 3, usually around 1,000rpm - 1,100rpm.

    I've tried:
    * Installing new spark plugs
    * Swapping coils (2 & 3, and 1 & 3 just to be sure).

    It's fine under heavy throttle and generally only misfires when I'm gently on the throttle. The car runs better once warmed up or if I after I drive it hard. Cold weather seems to make it worse.

    Any ideas what to check for next?

    [90,000 kms / 5 speed manual / no mods]

  2. #2
    Super Moderator Lucas_R's Avatar
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    Misfire - not Coils or Plugs

    Probably an injector thats clogged with carbon buildup given the km's on your engine.

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    Took it to VW village - they diagnosed a faulty injector (which has been replaced) and did an injector service. I also asked for carbon to be cleaned in the air intake after doing some reading (all up $1k in repairs).

    It's now running far, far worse than before, even after a long hard drive out of the city.

    Their mechanic thinks it might be fouled plugs from the service but I'm skeptical given it's the same symptoms... I'm wondering what else it could be (boost leak, faulty sensor etc.).

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    Super Moderator VADERR's Avatar
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    If it's spark/ignition cutting, it's usually only Spark Plugs, Coilpacks, or Injectors. Replace the cheap bits first. I've had issues with all 3 and misfiring on my GTI. Every time it was one of those 3.
    Driver Motorsport Tuned | Melbourne Car Meets | Insta: @RefrigerVADERR

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    Super Moderator Lucas_R's Avatar
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    If you still have the original ignition coils at 90,000km then i would definitely replace those. $150 will get you a full set from BMR Autowerks in Auburn. http://www.bmraw.com/r8-coil-pack-oe-genuine-4-pack/

    And when were your spark plugs changed? Were they done at the 60,000km service? If they have not previously been replaced, then it might be well worth your while to spend the $80 or so to get 4x new platinum spark plugs.

  6. #6
    Super Moderator VADERR's Avatar
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    Quote Originally Posted by Lucas_R View Post
    If you still have the original ignition coils at 90,000km then i would definitely replace those. $150 will get you a full set from BMR Autowerks in Auburn. http://www.bmraw.com/r8-coil-pack-oe-genuine-4-pack/

    And when were your spark plugs changed? Were they done at the 60,000km service? If they have not previously been replaced, then it might be well worth your while to spend the $80 or so to get 4x new platinum spark plugs.
    ^ This

    The Mk5 GTI also had a silent recall for Coilpacks.
    Driver Motorsport Tuned | Melbourne Car Meets | Insta: @RefrigerVADERR

  7. #7
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    Plugs were changed two weeks ago (>200kms); NGK Platinums. If I'd known they could be fouled from the injector service I could have put the old ones in beforehand.

    Thanks for the Coils link - cheaper than i was expecting so I might give them a go.

    I'm anxious of replacing everything and not solving the underlying issue though, which is why I took it in to to be diagnosed / repaired in the first place.

    One last symptom I didn't mention: if I rev and hold the throttle in a single position (like at 1,500 rpm), the revs won't hold still (i.e. they'll vary ~100 RPM either side erratically). Throttle sensors look fine in VCDS.

  8. #8
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    Have you solved this problem? Pull the sump off and check for metal or do a compression test on the miss firing cylinder. Sounds like you might have a dud piston.

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