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Fuel System Too Lean - Bank 1 and Cylinder 3 misfire.

Discussion in 'A3/S3 Forum (8L Chassis)' started by TDIQ, Jul 9, 2010.

  1. TDIQ
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    TDIQ 8L > 8P > 8V

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    My car's been acting up with a misfire.

    I've changed the coilpack for a brand new one, and cleaned the MAF this morning, but I'm still getting an error with Vag-Com saying bank 1 fuel system too lean, and that cylinder 3 is still misfiring.

    The car's down on power and running rough. What could it be? I was told it could be the spark plugs have been fouled from the misfire and also to change the leads.

    Any other ideas?

    Thanks
    #1
  2. TDIQ
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    TDIQ 8L > 8P > 8V

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    Changed spark plugs, cleaned the thottlebody and MAF. Still same problem.

    Thinking it could be the HT lead but I've also heard it could be lambda sensor, but I don't see why this would give me a misfire on cylinder 3 only. Any thoughts, anyone?
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  3. badger5
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    badger5 RIP S3dave Site Sponsor

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    what airflow does it log
    maf under reading also causes apparent lean condition
    block 032 will be +25% i guess

    what figures do you have?
    #3
  4. TDIQ
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    TDIQ 8L > 8P > 8V

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    Thanks for the reply.

    What's the best way to log airflow? Just drive about logging the MAF readings?
    The thing is, as it's only cylinder 3 misfiring, would it be something like the MAF as surely that would make all cylinders misfire?
    #4
  5. hharry100
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    hharry100 Member

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    Hey aaron It sounds like you may have a clogged/fault injector, this is the same problem i had and i bought a new bosch injector from euro***parts dont forget you should also change the seals when you remove the injector rail, i think the seals are only available from audi.
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  6. TDIQ
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    TDIQ 8L > 8P > 8V

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    Thanks for the reply Harry. I'll have to check if it's a fuel injector, but I've done a log in third gear up to pretty much the redline that could perhaps rule something out.

    [​IMG]
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  7. TDIQ
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    TDIQ 8L > 8P > 8V

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    Bill your last post isn't coming up on my phone, would you mind posting it again?
    #7
  8. fran-s3
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    fran-s3 Active Member

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    have you considered the fuel pump may be on it's way out? when mine was doing this the engine bay was roasting to. (more than usual)
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  9. big_mo
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    big_mo MOSES

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    I also have the same.... bank 1 fuel system too lean. I have been to my mate and changed the air maf is well as cheacked all hoses. Still no joy
    #9
  10. TDIQ
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    TDIQ 8L > 8P > 8V

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    The thing is, if it were the fuel pump surely it wouldn't affect just a single cylinder? It's only cyl. 3 that's the problem, so I guess it could be the HT lead or injector, which are the next things for me to try. The MAF readings seem ok, and surely that would affect all cylinders as opposed to one. I've changed the plugs and coilpack, so that's no worry either.
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  11. fran-s3
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    fran-s3 Active Member

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    True it effected all my cylinders! Ok cool well it's not that then lol. Yeah HT leads coil pack or spark plug would be my next bet...
    #11
  12. TDIQ
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    TDIQ 8L > 8P > 8V

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    Finally got a set of HT leads after ECP 'lost' them in the warehouse. Turned out it was the leads, which is nice as an injector from ECP or Audi was about £120.

    Thanks for the help everyone :D
    #12
  13. jimmp
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    jimmp Member

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    sorry to bring this up again as it has now gone down the list-

    Conversely, I get "system too rich bank 1" fault codes every month or so. Anybody any idea what this could be...?

    Thanks

    JimP
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  14. big_mo
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    big_mo MOSES

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    I have the same problem mate.
    Changed the air maf and cleaned the throttle body and realigned it deleted the code. Lasted a week till it poped up as i was going down the M40 at 80mph.

    Back to the drawing bored for me.
    Some one told me maybe a lambda probe
    #14
  15. Matt82
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    Matt82 Active Member

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    do you have a misfire with that too?
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  16. big_mo
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    big_mo MOSES

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    No i only get bank 1 fuel system too lean
    No misfire
    #16
  17. Matt82
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    Matt82 Active Member

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    bank one is lambda 1. its trying to lean the mixture and cannot lean it any further

    basically the exaust is too rich... i think you have a boost leak richening up your mixture
    #17
  18. jimmp
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    jimmp Member

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    Thanks Matt82,

    where should we look for that...?

    Thanks

    JimP
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  19. Matt82
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    Matt82 Active Member

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    almost any boost leak will have oil/gunge sprayed out from the leak

    prime suspect is the breather hose under the inlet manifold

    second id look at the connections into and out of the intercooler

    then around the compressor side of the dv.

    anywhere that sees boost really.

    lots to check tbh
    #19
  20. jimmp
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    jimmp Member

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    Thanks for that- I'll have a look tonight.

    JimP
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  21. badger5
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    badger5 RIP S3dave Site Sponsor

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    can you get it logged?
    cleaning a tired MAF rarely rejuvinates it
    a low g/s reading would confirm whilst logging.

    i would get this done first before you spend hours chasing other things where this is the most common cause
    #21
  22. s3dave
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    s3dave TFSI Hybrid

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    Whats happening on this site? loads of old posts coming up??
    EDIT: just read spammer.....:gun2:
    Last edited: Nov 25, 2010
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