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1.8T drop in MPG and misfire

Discussion in 'A4/S4 forum(B5 Chassis)' started by A4Chris, Mar 17, 2009.

  1. A4Chris
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    A4Chris New Member

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    [Mar 17, 2009]
    Whilst I know this will be a case of running a diagnostics (which I don't have easy access to) I'm just wondering if anyone has any 'starters for 10'?

    My average MPG on my 1.8T (AEB) has dropped from 35 to 26, idle is rough and misfires when under power (especially in 3rd gear for some reason). Also, low down torque seems to have gone and top end punch dissappeared. Basically running rubbish!

    MAF was replaced with an OEM replacement 16 months ago so don't think it's that. Thinking it could be an ignition coil? Also, worth noting that passed MOT whilst running like this so presumably emissions (and therefore Lamda sensor?) okay??

    HELP??
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  3. Sandip
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    Sandip Well-Known Member

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    [Mar 17, 2009]
    Could be the ignition amplifier module, its on the top of the airbox, has two plugs going on to it
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  4. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Mar 17, 2009]
    Either gnition module, in which case its usualy cyl 2 that goes first.

    I recently had much the same, my car would idle fine, and miss on high boost, turned out to be a coilpack for me. I am sad and actually carry spare coils and an ICM in the boot
    #3
  5. A4Chris
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    A4Chris New Member

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    [Mar 17, 2009]
    Thanks guys - I'll look into this further at the weekend. Might go down the route of replacing all 4 coil packs to rule coil packs out if nothing else - or hopefully fix the problem (looks like the coil packs are the original ones so at 145,000 miles old can't do any harm to replace them!)

    Thanks for the quick responses.

    Cheers

    Chris
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  6. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Mar 17, 2009]
    I would certainly do all four if you can, but i would play swappsies and find the culprit so you can keep the 3 "good" ones for spares, you never know....
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  7. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Mar 17, 2009]
    might want to check your spark plugs before changing any of the expensive parts...
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  8. richie_jones
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    richie_jones Member

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    [Mar 18, 2009]
    whats the best way to test if a coil pack is faulty, would this show in VAGCOM
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  9. g60leigh
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    g60leigh Well-Known Member

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    [Mar 18, 2009]
    anyone know how much a ignition amplifier module is ?
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  10. Spunker
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    Spunker New Member

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    [Aug 5, 2009]
    Sounds very similar to the problem i had, the garages i went to see did a few things that never worked like the MAF. In the end i got myself 1 coil pack and swapped it around all 4 of the old 1s, it turned out to be the last one i tried!
    #9
  11. mwarrey
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    mwarrey Member

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    [Aug 5, 2009]
    As far as I know, swapping each in turn with a known good one is the only way. The fault doesnt register in the ecu even with a major misfire. There is a way of testing the ignition module with a simple test rig you can make yourself. It shows you how here :- http://forums.audiworld.com/showthread.php?p=1535031
    #10

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