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1.8T misfire - can anyone help?

MikeA3 Nov 27, 2007

  1. MikeA3

    MikeA3 Active Member VCDS Map User

    Sorry for the rather long post but i thought it best to give the whole history of this problem so far:

    My S3 has a misfire on cylinder 1 which is causing the CEL light to come on, When i scan it with vag.com it reports codes 016684 & 016685

    016684 (as i understand it) is the general misfire code which occurs whenever any cylinder misfires

    016685 is the code showing the particular cylinder that is misfiring (cylinder 1 in my case).

    It's really noticeable if the engine is cold, when i first start the car, the revs are at 1200rpm and it's not too bad, as soon as it drops to it's normal idle of 800rpm you can feel the vibration through the car, to prevent this, I'm giving it a couple of hundred extra revs when stationary which seems to smooth it out. When driving, the power delivery is smooth and there are no noticeable "jumps" when i put my foot down, it just seems like I'm a bit down on power and the car isn't ticking over properly at idle.

    If I have the engine running and the bonnet open, I can hear a ticking noise coming from within the engine bay, (I'll take a video of it and post it a bit later on, If anyone could anyone tell me if this is normal noise it'd be appreciated)

    So far I've done the following to get to try and solve the problem:

    Replaced all 4 original coil packs, I've also tried swapping coil packs over but the fault doesn't move cylinders so I replaced cylinder 1's again but this didn't solve the problem, also the coil pack doesn't seem to be popping up which could cause it to "miss" the spark plug. so I'm pretty sure the coil pack isn't at fault.

    Replaced the spark plugs twice - The original plugs were replaced with OEM ones at a service some 3 months back, the problem continued so I took the car back and the garage replaced the OEM plugs with heat range colder ones to in case the plugs were overheating causing the coil pack to fail.

    They also did a compression test - no problems found

    I've also put some injector cleaner into the fuel tank just in case it was a sticking injector causing the problem, and I cleaned the MAF sensor as per wak-tt's guide but it's not solved the problem

    So - what's next to check, i was thinking it could be an electrical problem, perhaps a damaged wire somewhere in the loom but i can't seem to work out how to get the silver heat shield off without damaging it - does anyone know?

    or - perhaps a fuel pump problem - But i would have thought if this was knackered it's cause all the cylinders to misfire not just one

    If anyone has had similar problem or could point me in the direction of what to check next it'd be very appreciated.


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  3. petewon

    petewon Registered User

    Perhaps a problem with the ignition controll module or the cable between that and the coilpacks??

    Heres a tutorial for testing the ignition module on other models. It may point you in the right direction http://forums.audiworld.com/a4/msgs/1594531.phtml

    Just a thought.
  4. enda1

    enda1 Registered User

    Whats the engine code. 2 things to look for
    The timing of the inlet camshaft is controlled according to engine load and engine speed. The electrically operated solenoid valve for camshaft adjustment transmits oil pressure to the mechanical camshaft adjuster as required.
    The hall sender reads the position of cylinder 1 and sets timing accordingly, but if this fails it goes into a safe mode. You might want to check out this hall sender as well. If you need to change the camshaft adjuster valve then you need a special tool to hold the timing chain but if you get to this stage send me a mail and I’ll forward you the procedure.
  5. MikeA3

    MikeA3 Active Member VCDS Map User

    Thanks for the reply, The engine code is AMK - it's the 210bhp lump


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