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AGU Misfire, only when hot and under 10psi boost or more.... Coilpacks?

Discussion in 'A3/S3 Forum (8L Chassis)' started by Prawn, Feb 22, 2010.

  1. Prawn
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    Prawn My other car is a MINI!!!!

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    guys, I've been ahving problems now for a few months with a misfire.

    Strangely, when warming up, and for a few minutes when it's up to temperature, it's absolutely fine, but it seems that when it's been warm for more than a few minutes, the problem starts.

    Driving around slowly, the car is 100% fine, and drives normally, even at part throttle, provided boost doesn't exceed about 8-10 psi, it'll pull right through the revs problem free.

    The problem is, when i floor it, and it boosts over 10-12 psi, it starts to misfire VERY badly.

    i first thought this was due to old plugs, so replaced the plugs with brand new iridium densos. No change.

    I then thought, much like Welly, that it might be the coil pack wiring insulation breaking up, allowing the wires to short. I stripped it all back this weekend, to find all the wiring still perfectly intact, and still very flexible. I retaped it all, and the problem is unchanged.

    This leaves me to think it's the coilpacks breaking down under heat/high load.

    Has anyone ever heard of AGU coilpacks blowing before? under heat and load only?

    id there anyway to tell which coilpack is blown on an AGU?

    Am I able to scan for misfires in VAGcom on an AGU>? module 1 shows no faults at all.

    Any ideas would be much appreciated, I'm off to the ring in 6 weeks, and really need to get this sorted!

    Cheers

    Nick
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  2. 16Klappe
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    16Klappe Princess Slayer

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    Sounds fubar'd to me, best bet would be to try and find somebody to sell it to. Preferably somebody who's close so you can keep an eye on it and make sure its getting looked after...
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  3. Prawn
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    Prawn My other car is a MINI!!!!

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    Feck orf Jardo, I'm not selling you my car! (yet)
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  4. HTC
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    HTC Active Member

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    Hitachi colis are pretty much bomb proof, but you can't rule it out if you haven't swapped them. Can you borrow a set anywhere? I'd let you borrow mind but I'm away at the moment.

    Can't remember which fuel pump you have, but I'd check that and also your fuel filter.
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  5. Prawn
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    Prawn My other car is a MINI!!!!

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    I'll see if I can borrow a set of Coils from a mate kev, I'm hoping it's the problem.

    the fuel filter was new about 30k ago, the pump is a 4 bar LCR pump. I think it's unlikely to be the fuelling, as when it's just got up to temp, it pulls perfectly, and records 188g/s maf readings, suggesting around 235bhp. I can't work out how the fuel pump would be effected by engine temperature.

    I did find another very old thread suggesting it could be the ignition amp mounted in the airbox. I guess I need to find a friendly mate with an AGU who doesn't mind me testing out a bit bits.....
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  6. badger5
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    badger5 RIP S3dave Site Sponsor

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    hitachi are'nt fail proof.. better than most but fail just the same in the conditions they have to operate at
    seems most likely coil pack being under boost relatred misfire.
    ign tcs unti might be on the fritz perhaps.. the one which heatsinks into the stock airbox
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  7. Prawn
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    Prawn My other car is a MINI!!!!

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    Thanks Bill. I'm going to try and ask a friend nicely if I can pop his parts onto mine to see if it cures the issue.

    If it is the ignition module, what's it's proper name? I've always thought it's an ignition amplifier, but to be honest I'm not sure if that's correct.
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  8. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    The ICM tends to fail on cyl 2 fisrt for some reason. I had a similar issue with coils and ended up playing musical coilpacks on the side of the road till on boost missfire had gone. IE change no1 for a known ghood one, blast a bit, prob exists stil so put pack removed from one into cyl 2 and so on and so forth.
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  9. Prawn
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    Prawn My other car is a MINI!!!!

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    Interesting Mark, I'll find out at the weekend hopefully what's the cause!

    the lovely custard has offered the use of his AGU powered A3 for parts donation. I'll start by swapping over the coilpacks and see if that cures it, and if it doesn't, I'll try the ICM. If that doesn't fix it, I'll scrap the bastard and buy an S3 instead!

    this HAS to be sorted before I head to the ring at easter! Not worth going otherwise.....
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  10. Welly
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    Welly VX220 SC Driver :)

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    Power Output Stage Module N122. Part number 4D0 905 351
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  11. Prawn
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    Prawn My other car is a MINI!!!!

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    What a legend.........
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  12. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    Show off :lmfao:
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  13. 16Klappe
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    16Klappe Princess Slayer

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    Awesome, I wonder how much he would want to sabotage one of his coil-packs...
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  14. sportstractor
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    sportstractor Chugger

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    probably do it for a bowl of custard or a peice of cake mate:icon_thumright:
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  15. Custard
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    Custard New Member

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    Hey i never agreed to this ?!?! Prawn just said his guna come round and buy me loads of Custard! i knew it was too good to be true!!!


    :p
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  16. frenchman
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    frenchman Member

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    Remember to stock up for the Ring Dave, no custard in Krautland!!
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  17. Custard
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    Custard New Member

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    Yeah i was saying to james earlier, looking forward to some custard with kissen nugat!

    sorry Nick back on topic
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  18. Welly
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    Welly VX220 SC Driver :)

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    I only know because I thought mine was dicky and I did a bit of research..... lol :)
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  19. feville
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    feville Frank

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    My ignition amp went last month (similar symptoms), i changed plugs + packs + had loom all over the place looking for breaks before i changed it....

    Got mine from GSF for £55 + vat :icon_thumright:
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  20. Prawn
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    Prawn My other car is a MINI!!!!

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    cheers dude, the way it feels when it does it, its as if it's more of a general ignition issue than a coilpack problem, which is making me think it's the ignition module and not coils.

    Today it practically created it's own antilag system, started popping at about 2200rpm and the turbo spooled up despite me not accelerating at all :S most bizzare!
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  21. Prawn
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    Prawn My other car is a MINI!!!!

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    Decided I'm sick of this misfire I've been having, and as it only happens on boost, I decided to unplug the N75 to limit boost to actuator pressure only, so 5psi. following something Bill said in Wellys thread.

    The drive is really smooth on 5psi, although obviously it's much slower as there's no mid range torque, the misfire is totally gone, so I can live with it being slow!

    Dyno style plots from VAGCOM are interesting though....

    Here's the plot before the misfire, running around 18psi boost:

    [​IMG]

    Then here's the plot from this morning, with the N75 unplugged, running 5psi from the actuator, with a tiny bit of creep top end to 6-7psi

    [​IMG]

    Such a flat curve, with a bizzare almost vtec like kick when the wastegate starts to creep. Drives totally like an n/a car, although still makes impressive top end power.
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  22. Welly
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    Welly VX220 SC Driver :)

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    In which case, why not buy an MBC and drop the boost to 15.5 PSI. Mine used to do exactly what you describe under full load boost, but it wasn't a misfire.

    Turns out the ECU was calculating MAP pressure via an algorithm and cutting the spark to the coils when it saw too much. This is why it feel sooooo violent when it does it, you almost hit the steering wheel! It only did it at 16 PSI or over.

    I installed an MBC and fiddled with it until it was about right. 15.5 PSI is the charm.
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  23. Matt82
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    Matt82 Active Member

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    i cant see the damn pics, but without the massive slug of 20vt torque in the mid range, sounds like a more usable power delivery!
    #23
  24. HTC
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    HTC Active Member

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    As mentioned last time we met ... Standalone programmable EBC :icon_thumright:

    IMO a must have for the AGU engine. Hope you get the miss fire sorted though.
    #24
  25. Prawn
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    Prawn My other car is a MINI!!!!

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    Interesting Welly, but I can't see why it would start doing it after 2 years of running OK! When first mapped it ran at 22psi with no trouble at all, and was proper quick. The turbo has since seen better days, and has a few cracks in the housing now, but up until recently it still ran 18-19psi just fine, and it still does now every morning when it first warms up, it's only when it's been hot for 10 minutes or more that it becomes a real problem.

    Kev: I know an EBC is the future, but I just don't want to spend the money on this shed any more. I'll be looking to move it on towards the end of the year anyway, assuming I don't stack it at the ring sometime in summer.... The mini project is much more important these days
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  26. Welly
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    Welly VX220 SC Driver :)

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    In which case mate, disregard. I can't see why it would just 'start' doing it either! Bloody cars!!
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  27. Prawn
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    Prawn My other car is a MINI!!!!

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    Mine did exactly what you describe on the ko3S when it had a revo KO3 map.....

    Was fine for 2 years on the custard code phase 2 though
    #27
  28. Welly
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    Welly VX220 SC Driver :)

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    Yeah, she's on REVO Stage 1 so that sounds about right. Used to drive me spastic! You'd be mid-overtaking something and the power would just die!
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  29. Prawn
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    Prawn My other car is a MINI!!!!

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    What are your thoughts on the benefits of gear specific boost and the gain settings Kev?

    I'm tempted to try an EBC, as I'll need one for the Mini anywaym, but I'm not prepared to spend £400 on an AVCR. I've been looking at the Gizzmo EBC, which costs £200, and has 6 programmable settings, but doesn't have the gear specific boost option, or gain control, it just controls the upper limit
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  30. badger5
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    badger5 RIP S3dave Site Sponsor

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    if its flowing "too much air" as far as the MAf's concerned... then some folks try using a 4v7 zener diode across the maf sensor output so it cannot hit the 5v (or close to) threshold where it throws a wobbler

    misfire wise.. new, correct type plugs been tried? I know its stating the obvious, but for me, I chased a similar thing, not imagining it was the plugs (they were'nt old) and bugger me, it cured my then misfire under boost.
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  31. Prawn
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    Prawn My other car is a MINI!!!!

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    I had been running denso IK22's for 2 years Bill when the problem started, having covered some mileage, i decided to change them again. I went down to my local eurocar parts, who recommended me IK20's for my car, so i fitted them 2 weeks ago, brand new of course...
    #31
  32. Welly
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    Welly VX220 SC Driver :)

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    Bit of a billy bodge though isn't it really? Surely if the MAF doesn't report correct air flow you will never get correct fuelling....?
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