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  1. #1
    Geeman's Avatar
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    VAG COM fault code readings... possible coil pack gone down?

    I've had some REALLY strange problems with my A4 today.

    Been on a mammoth road trip (11hr round trip) and everything was going fine until I got to my second stop. Did what I needed to do, but when I came back to the car it wouldn't rev, then revs kept dying, the it would cut out. This carried on for about 2 minutes... It idled fine... but as soon as you touched the trottle it would rev for a split secind, then just die.

    Managed to get it rolling on minimal revs, slowly built the speed up and then it was okay! Fine for the rest of the journey till I got to my next stop, then the same happened again. Rinse and repeat for about 5 more times.

    So, got home and hooked up fault code reader.

    17834 - tank ventilation valve - open cricuit - ALWAYS got this fault. Still trying to remedy that.
    16486 - MAF (G70) : signal too low - ALWAYS got this too... (since the engine bay fire) trying to trace the wiring back to the ECU from the MAF tomorrow to check for continuity.
    17964 - change pressure control : negative deviation - Limp mode (had this a few times before as well)
    18010 - power supply (B+) terminal 30 - low voltage - caused by me removing connectors to re-set TB as I thought it might have something to do with it.

    From those 4 codes, I can't see anything that would casue what happened today.

    What are the symptoms of a coil pack going down? Anything like i've described?

    Could the fuel pump relay (J17) be the problem? Apparently that's a possible solution to fixing code 17834

    Any of your thoughts would be greatly appreciated.

    P.S. - car is sat on my drive with EXACTLY 100,000 miles on the clock. Gutted. lol
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  3. #2
    "Stick a V8 in it!"

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    Dead maf is probably causing your Charge pressure code.

    Unlike the S4 chaps, yours says "Negative deviation" ie your not getting enough boost, rather than too much.

    You need to sort the wiring to the MAF and the Tank vent valve, and go from there.

    18010 appears on craigs S4 a lot, its related to battery voltage, but if the engine kept dying and you kept having to start it again, you were probably just draining the battery down.

    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
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  4. #3
    Geeman's Avatar
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    I disconnected the battery terminals to re-set the TB (thinking that was the problem) so I know that caused the 18010 code... no worries!

    You're right... I need to sort the MAF wiring out then. It's defo not the MAF itself (I hope) as the new one displays the same problem as the old one. It can only be the wiring I think.

    Just strange that I got the really weird symptoms I got today though. Will see if it still does it tomorrow when it's cooled down...

    Think I might have to buy a new N80 valve, as the replacement I put on it was second hand and could be faulty itself! The 17834 code has been with the car ever since I bought it... (Mark and Lee looked at it for me at International last year and it was there then (pre-fire).
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  5. #4
    mwarrey's Avatar
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    Doesnt sound like a coil pack, these tend to give problems under load rather than at idle.

  6. #5
    Geeman's Avatar
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    It idles fine... it's when you rev it or try to set off it struggles and the revs die.

    Mind you, even at idle, you can hear it slightly popping from the exhaust...
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  7. #6
    Geeman's Avatar
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    Update... disconnect MAF, started the car and it's running exactly as it was before. So I've effectively been running without a MAF for 6 months.

    Checking wiring now... Got the ECU out, disconnected... just got to find the right pins to check continuity.

    Anyone wanna talk me through it, my number's 07764 576659... LOL
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  8. #7
    "Stick a V8 in it!"

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    The diagram i posted the other day has all the ECU pin numbers on it, so you should be able to get everything from that.

    How you getting on?

    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
    Geeman's Avatar
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    I've done it!

    WOO HOO!

    Thank you for your continued support on this fella. It was (and still is) very much appreciated!

    It's running like a dream now. I've laid it up for the next week to give it a well-earned rest while I put my newly built Mk3 through its paces so that I can put it up for sale knowing there's nothing wrong with it.

    Again... thank you very much for your help and advice.
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