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A3 1.8T misfiring...

Discussion in 'A3/S3 Forum (8L Chassis)' started by Tiger, Apr 15, 2009.

  1. Tiger
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    Tiger New Member

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    A couple of occassions now i've noticed my car only firing on 3 cylinders, usually not for more than a couple of seconds every couple of weeks maybe.

    I just started her up today (first time since last friday) and she was horribly misfiring along the motorway with the engine both cold and warm.

    As I came off the motorway she was ok again and rocketed along at full power. The idle has been a little lumpy for a while but mainly when running cold. I have no warning lights on and the car hasnt been modded and like I say, when the car is running fine there's no loss of power at all and the turbo is winding up fine.

    Any ideas before I change HT leads and check plugs?

    Cheers.

    Ben.
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  2. SnoopS3
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    SnoopS3 You cant beat German

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    Hey,

    It could be the coil pack, main reason i say this is that its a common issue. Also it seems one of mine has just failed me!

    Not 100% its the same problem as me as you say its misfiring now and again? whereas mine was bouncing between 3 and 4 cylinders constantly.

    Maybe one is on the way out...
    #2
  3. abdus
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    abdus Top Gear

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    what engine is it?
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  4. ash_pearce
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    ash_pearce Member

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    been covered many times, search function will be your best friend on here, people get fed up saying the same old thing.

    However.. get it check on vagcom for any faults first. You can swap plugs coil packs all day long and still have a missfire. Also if you have a agu engine you will have a ignition amp on the side of the airbox, prone for failure. Mine has been missfiring recently turned out to be the maf plug wasn't plugged in correctly.
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  5. HTC
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    HTC Active Member

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    Also check wiring to the packs.
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  6. VAGary
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    VAGary New Member

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    check your hoses! i had a split hose and it had same symptoms
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  7. Tiger
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    Tiger New Member

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    Well, its not done it again for a few days now apart from a 3 second spell of misfire when cold the other morning.

    I looked at coil packs on GSF and they were showing up at up to 40 odd quid depending on my engine code which I havent found out yet, this seems to be a good starting point (from other posts i've read anyway) then the ignition amp (should my engine have this) then i'll look at MAF. After that point i'll take it to the local Audi specialist round the corner.

    Any idea of prices of MAF? and Ignition Amps?

    Where exactly do I find my engine code?
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  8. abdus
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    abdus Top Gear

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    MAF- I paid £68 iirc on exchange
    Ignition Amp- £72 from murraysdirect
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  9. abdus
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    abdus Top Gear

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  10. HTC
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    HTC Active Member

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    If it says "AGU" then it won't be the coil packs as they never fail, but it could be the ignition amp on the airbox. If it says anything else then it could be the coil packs. On all types, check the wiring for cracks and breaks. Give the plugs to the coil packs a wiggle.

    To rule out the MAF, unplug it and drive around to see if it missfires again. The engine will be a bit down on power when unplugged, but that's normal.

    Lumpy idle might suggest a vacuum leak. Common place is at the breather pipes under the inlet manifold. Look for oily marks in that area and around the pipes. Also wiggle the injectors with the engine running and listen to the engine note. Injector O rings can leak.
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  11. Tiger
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    Tiger New Member

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    I had a look and i've got the ignition amp on the airbox, at the top and to the rear held on by 2 hex head bolts. I'll look at getting another and replacing it and i'll keep you posted. The only thing i'm worried about is the fact that the fault is so intermittant, I would have thought that if it was my Ignition Amp then it would just go and that would be it but i guess its as good a place to start as any.

    Cheers.
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  12. abdus
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    abdus Top Gear

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  13. Tiger
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    Tiger New Member

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    I had just looked at that actually. Again though, If its intermittant it might not show up a fault anyway though, this is why I hate intermittant faults. I'm a electrical engineer by trade and intermittant faults are a real scurge :lol:
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  14. abdus
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    abdus Top Gear

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    mine had the same problem as yours and it was intermittent. When I tested it, it showed the fault. It finally died..lol
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  15. Tiger
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    Tiger New Member

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    Any idea of the part number? Going to give Murrays Direct a call.
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  16. abdus
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    abdus Top Gear

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    ask for this:

    VW & Audi 2nd Stage Power Output Ignition Unit
    #16

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