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Thread: 1.8t misfire

  1. #1
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    1.8t misfire

    Well the car survived the 8 hour drive home after I bought it and driven a few times since then but having problems now

    Drove to shops in town earlier, all was fine but when came back and turned ignition I noticed rough shaky idle. Same when driving but no warning lights so I just limped it gently 10 mins up the road home.

    I'd already ordered vgcom lead but likely won't deliver until Wednesday next week. From what I've read I assume most likely guesses at this stage would be coils or ICM? Maybe?

    Anything more I can check without vagcom/replacement parts just now to narrow it down?

    Thanks

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  3. #2
    "Stick a V8 in it!"

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    Does it sound a bit like a scooby?

    If so its running on three and its ICM or Coils, if not it could be an airleak somewhere?

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
    2000 A4 1.8T Sport Quattro Saloon, Black-ish
    1997 S4 - PPC £999 Challenge Track Car Build
    TD5 Land Rover Defender build


  4. #3
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    Yup, definite scooby sound.

    Checked it again an hour after home and was still running rough, just been out again and is now idling and revving as normal??!

    Left it to heat up and tried again but all still ok. Car hasn't moved and I didn't find anything loose or disconnected when I first checked so nothing really should have been fixed?

    Would the coils or ICM suffer from intermittent fault or does this suggest wiring issue maybe?

  5. #4
    "Stick a V8 in it!"

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    Ye they can be intermittant to begin with, usually get worse when hot.

    Might be worth dropping a new set of spark plugs in, and when you do it look to see if any cylinder is obvisouly different to others.

    The ICM's apparently seem to like dropping Cyl2 first,

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
    2000 A4 1.8T Sport Quattro Saloon, Black-ish
    1997 S4 - PPC £999 Challenge Track Car Build
    TD5 Land Rover Defender build


  6. #5
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    I'm sure the seller said he had just done new plugs and coils but won't hurt to swap and like you say I can have a check of cylinder 2 also.

    Going to head out for another run now to get temps up and see if it goes again.

    Cheers for the help.

    I see you're in Bo'ness, I'm just over in Falkirk

  7. #6
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    Hi, I have had a coil pack and ICM go on my 1.8t in the last 3 months !. Unfortunatley neither of these issues showed up on VAG COM.

    The difference between the 2 in my experience was that the coil pack was more intermittent and quite a severe misfire under load. So at idle it wasnt so noticeable but under acceleration it would lurch and misfire, much worse below 4000 rpm. The only way I managed to identify the faulty coil was to change each one in turn with a known good one. There was no significant difference in spark plug appearance.

    The ICM fault on the otherhand was there all the time and not a quite so severe misfire. I found an article on Audiworld on how to test the ICM :-
    http://forums.audiworld.com/showthread.php?p=1535031
    and found the problem on mine (No 3 cylinder). I managed to find a genuine one at GSF for 55.

    Good luck

  8. #7
    "Stick a V8 in it!"

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    Vagcom (well the ECU) cant really tell theres a fault with these components, as the ICM effectively "hides" the coils from the ECU.

    The early cars also cant do any missfire detection, so you get nothing at all on vagcom.

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
    2000 A4 1.8T Sport Quattro Saloon, Black-ish
    1997 S4 - PPC £999 Challenge Track Car Build
    TD5 Land Rover Defender build


  9. #8
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    Yeah spotted that ICM test page earlier n bookmarked it lol.

    It's obviously worse under acceleration but even at idle I could feel it as soon as I started the motor, rough and a noticable car shake. Read in another post a good description of it when driving, there's a lack of power like it's "hunting for revs" and the shake gets worse while accelerating.

    Had the car out to get some temp up, stopped and restarted but it's running totally smooth again. I'll obviously need to get hold of a few spare bits to swap out for next time it goes though.

    Cheers.

 

 

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