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  1. #1
    jay1601's Avatar
    5th Gear

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    random misfire/judder

    car has started to play up over the last 2 days

    it will randomly judder. feels like a light misfire. when i come onto boost it will judder then after about 4/5 seconds it will be fine. no fault codes/EML

    going to start with replacing the plugs (done about 12K on current plugs bosch super 4's)

    engine: AGU

    with it being xmas haven't got a massive amount of spare cash at the moment. so don't want to go replacing random bits for the sake of it.

    been looking around online seems like the ignition amplifier seems like this comes up alot when searching for misfires on the 1.8T lump. would this be a good place to start after plugs ?
    Audi A3 8L 1.8T breaking.
    front bumper, impact bar, slam panel, full engine and loom sold.
    everything else for sale.

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  3. #2
    jay1601's Avatar
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    stuck new plugs in made no difference.

    tested the ignition amp using this guide
    AudiWorld Tech Articles

    got around 200 ohms on all 4. so doesn't look like its that.

    coils ?
    Audi A3 8L 1.8T breaking.
    front bumper, impact bar, slam panel, full engine and loom sold.
    everything else for sale.

  4. #3
    Gops's Avatar
    6th gear @7000rpm

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    Coilpacks are the most common issue if a misfire on the engines. Coilpacks can be tempremental so advice is to change them.
    Quote Originally Posted by <tuffty/> View Post
    its either mapped or broken...

  5. #4
    Oke Phill's Avatar
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    Quote Originally Posted by Gops View Post
    Coilpacks are the most common issue if a misfire on the engines. Coilpacks can be tempremental so advice is to change them.
    +1 for sure!

  6. #5
    Vex182's Avatar
    Guess what I drive...

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    Agree with coilpacks, you did not use Super 4s again did you? NGK all the way! I melted a set of super 4s and Badger5 say they don't get on well with those plugs too.
    Silver 2002 Audi S3 225 (BAM) since March 2011.

    Mods: Badger5 2.2 TIP, Jetex filter, PCV delete, 710 DV, N249 bypass, R-Tech Stage 1 TiV Remap, Audi TT Pedals, Red Dogbone, Polybushed tie arms. All silicone boost pipes, Michelin PS3s, Red V6 coil packs, MK4 flat blade conversion, retrofited cruise control.
    Currently: 254bhp - 276lb/ft (174bhp/ton) as of 11/02/2013 On V-Power

  7. #6
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    With misfire issues start with coilpacks
    if they are fine (tested by swapping them around to see if the misfire changes cylinder), then check spark plugs and the coil pack loom.
    If its spark plugs they will be coaked up with black soot or have evidence of arcing between points. Dirty brown colour is fine and normal.
    Loom is easy - if you have splits and can see exposed wire its either knackered or will be giving you more issues soon. You'll need to keep tracing back along the loom until the splits stop, and then solder a replacement loom in. Sounds scarey but its easy if you take your time.

    If all above is fine check vacuum lines - youll hear a hissing noice while engine is running. Thats a vacuum leak.
    Check boost pipes

    If its none of them and vagcom isnt helping the you'll need to check your compression.
    It going to be either be piston rings (blue smoke from exhaust?) or head gasket (white smoke from exhaust, mayo like substance on oil filler cap/dipstick, coolant level going down).

    A compression test will help you here (search youtube) and a sniff test on expansion tank for head gasket (goto a garage)

    Following that above should help you solve an misfire issue.
    Audi S3 [AMK 1.8T]

    Mods:
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    Revo STG 1
    Rota Grid Drift 9.5J alloys
    AP coilovers
    PCV oil catch can (to atmosphere)

 

 

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