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Random misfire a3 1.8t agu

Discussion in 'A3/S3 Forum (8L Chassis)' started by AGU-TURBO, May 21, 2011.

  1. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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    [May 21, 2011]
    got my head the other day off mush and eveyrthing is running sweet apart from a random misfire, started up yesteeday morning and tryed to set off and started misfiring and cut out, started it back up and came home and eventualy stopped misfiring. switched it off and made sure all pipes were connected properly and leads to coil packs were connected properly. everything seemed fine and took it round block and was spot on, so desciede to take it for a good run and did 60 mile with not hitch apart from it not boosting properly, normaly boosts to 1 bar and is only boosting to 0.7-0.8. anyway got up this morning and did about 7 mile and was coming to end of dual carriage way and started missing again then cleared again as i was going round the round about then did it a further 4 times till i got home (4 mile)

    anybody got any sugestions, i have changed the spark plugs tonight for some denso one's and still does it, have disconected n75 which oviously drops it to actuator preasure which seems to be about 0.4 - 0.5 bar so i no that is doing somthing lol, i have also pluged into vag-com and doesn't bring any faults up at all, i would of thought that if one of my coil packs were down it would throw a fault code what do you think?

    RANDOM MISFIRING

    LOW BOOST NORM 1 BAR NOW 0.7 - 0.8 BAR

    any help would be most appreciated, thanks
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  3. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [May 21, 2011]
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  4. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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    [May 21, 2011]
    Thanks i will look into that
    the plugs that i had in were bosch super 4's and the car was misfiring about every 5 seconds on idle, put my old denso's in and this stopped.
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  5. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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  6. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [May 22, 2011]
    Not that I am aware of, misfires will show but no actual fault code that I know of...

    AGU has the ignition amplifier doesn't it? it could be faulty... I have no personal experience of these but there are a few threads describing similar issues IIRC... the ignition amplifier is normally bolted onto the air box..

    <tuffty/>
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  7. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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    [May 22, 2011]
    Thanks tuffty yeh it has a ign amp, im pretty sure if that would fale it would misfire on all 4 cylinders's, but could be wrong. i will keep investigating, any ideas on the low boost
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  8. Prawn
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    Prawn My other car is a MINI!!!!

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    [May 22, 2011]
    The ignition amp going won't cause all 4 to miss for some reason, mine didn't!

    Bin the densis big time though, I had the same issues, replaced my old densos for new ones and it did it didn't solve it. Spent a fortune on other bits because i ignored everyone who told me it was plugs, and in the end, it WAS the evil densos. Never using them again!
    #7
  9. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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    [May 22, 2011]
    Hi prawn how was the car behaving when you'r ign amp failed. Was it randomly misfiring? Yeh ive binned the denso's and put my Bosch 4's in.
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  10. s3dave
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    s3dave TFSI Hybrid

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    [May 22, 2011]
    Yep ignition amp...
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  11. Prawn
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    Prawn My other car is a MINI!!!!

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    [May 22, 2011]
    Just really random, sometimes it'd misfire, so sometimes it'd be fine, often started to fail when hot, and usually fixed itself for a while.

    Now run standard NGK plugs and they're great
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  12. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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  13. Welly
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    Welly VX220 SC Driver :)

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    [May 22, 2011]
    Won't normally throw a code, no. I can't remember the exact amount.

    It is actually called the Power Output Stage module N122. Part numbers are 8D0 905 351 or 4D0 905 351.
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  14. Welly
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    Welly VX220 SC Driver :)

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    [May 22, 2011]
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  15. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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    [May 22, 2011]
    Thanks welly, ive just been out to check to make sure everything is connected properly and i noticed that the pipe that comes from actuator has a t-piece and splits off to tb and charcoal canister well..... i put them back the wrong way round - what a dum ass mistake. i put the pipe with the 1 way valve to charcoal canister and the other to tb lol :keule:. So oviosly the charcoal canister couldnt vent fumes back to tb but tb would of kept preasurising the charcoal canister and - fuel line i think, but i was wondering if this could be somthing to do with any of the problems if been having?
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  16. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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  17. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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  18. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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  19. Welly
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    Welly VX220 SC Driver :)

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    [May 23, 2011]
    Hmmmm, not sure what the effect of that would be, but I can't see it causing misfires. That's not to say it wouldn't though...
    #18
  20. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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    [May 23, 2011]
    ok, i presume i carn't log boost with vag-com be been that i don't have a map sensor with it being agu, anyone confirm this, thanks
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  21. Welly
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    Welly VX220 SC Driver :)

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    [May 23, 2011]
    Confirmed.

    Fit a boost gauge.
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  22. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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    [May 23, 2011]
    Yeh ive got a boost gauge and it used to boost to 1bar but only reaches 0.7-.08 bar now. i just wanted to see what requested boost was vs actual. but thanks confirming that. cheers welly
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  23. Welly
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    Welly VX220 SC Driver :)

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    [May 23, 2011]
    No probs. I remember what a pain that was when I had my AGU in an A3. No block 115. No block 118.

    The key to the AGU engine is the MAF. EVERYTHING is calculated from the MAF, it tells the ECU 99% of what it needs to know.

    Everything on the AGU is worked out via airflow. The ECU does know what boost there is as it has an algorithm to calculate boost from air flow vs TB angle.

    Any problems with an AGU engine, check the MAF! lol
    #22

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