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3.0 misfire problem - running out of ideas...

amiller001 Dec 28, 2007

  1. amiller001

    amiller001 New Member

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    Hi, I have a 2002 A4 quattro sport 3.0. It has had problems with misfires. Coil packs have been changed, so has the ignition wiring loom, as the coil pack connectors were cracked. This has improved it considerably, but still there are occasional random misfires. Not enough to trip the warning light, but on vagcom I can watch the counters on all cylinders go up, and you can feel the car twitch at idle as the misfires happen. I am wondering if this is a vacuum fault? If I open the oil filler cap, it creates the same symptoms.

    Also, when I am driving hard, the red BRAKE can come on for just a few seconds. I can't believe I emptied the resevoir. Is this a related vacuum fault?

    Please let me know any thoughts that could help me!
    Cheers
    Andrew
     
  2. RGBArgee

    RGBArgee Guest

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    I have know replacement Coil pcks to be faulty, had problem on my 52 V6 Cabriolet, and mate recently experienced with 1.8 225 TT. (He had 4x new ones and one failed almost straight away!)
     
  3. dan_b

    dan_b Member

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    I've also heard of the wrong coilpacks being installed - the 3.0v6 packs are not the same as the 1.8T packs, or indeed the later 3.2v6 packs...

    Does sound odd though with the brake warning coming on; I don't believe in coincidences, so could well be a related vacuum fault.
     
  4. amiller001

    amiller001 New Member

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    Thanks for the suggestions.
    I have checked the coil packs and they seem OK. They were were fitted by Audi Camberley, and they look the same as the ones that came off, so I think they are right. Its just had its 80000 service too and that didn't highlight anything.
    The thing that puzzles me is that the misfires are random across all 6 cylinders, so it must be a fault not local to one cylinder, which seems to rule out the normal injectors/coils/plugs. Any other ideas?
    I had one suggestion that the BRAKE dash warning could just be the fluid in the resevoir moving under heavy turns/braking so that the fluid warning light came on. Is this realistic, anyone else had this? If it wasn't new year, I'd just go and get some and top it up a bit to see!

    Still puzzled......
     
  5. dan_b

    dan_b Member

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    Are any fault codes are being logged? Does the misfire get worse under load?
     
  6. Administrators

    Administrators Administrator Staff Member Administrator Audi A4 TDi

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    Almost happy new year (21.17pm)

    Yes the brake light is more than likely the fluid level MK4 golfs seem to get this quite a lots.

    As for the misfire how many miles has the car done? I have not see it on the 3.0 but the 2.7T can get misfires due to cylinder leakage. The problem normally only appears and idle and low rpm. Logging is only going to show you the misfire at low rpm as it turns off at higher.

    Might be worth doing a Cylinder leak check (not compression test, it would be pointless)

    Best of luck

    A
     
  7. amiller001

    amiller001 New Member

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    I can see the misfire count going up on vagcom, but it doesn't go high enough to trip the misfire code, so no code is stored. It happens on all 6 cylinders.
     
  8. amiller001

    amiller001 New Member

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    Its got 85000 on it. You are right about it being a low rpm issue. I will see if I can test the leakage.
    Thanks
    Andrew
     
  9. dan_b

    dan_b Member

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    A couple more thoughts - what fuel are you running?
    Does the misfire only happen when the engine is cold?
     
  10. amiller001

    amiller001 New Member

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    Hi Dan,
    I have tried it with 95 and 98 octane - no difference. Going to chnge the plugs this w/end, and see if that helps.
    Cheers
    Andrew
     

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