1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Misfire at 3-4k. How to find and resolve?

Discussion in 'A3/S3 Forum (8L Chassis)' started by Bad Sir Culation, Jan 12, 2014.

  1. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
    As mentioned in my fault codes thread, the injectors are all showing an pen circuit. Could this affect the car enough to cause a misfire at 3-4k at around 3/4 throttle or above?

    Also, I found a melted connector plug for my N249 and the N249 itself has vanished. Unfortunately it's been left hanging at the back of the engine as I have obviously forgotten to cable tie it up and it's sat right against the block by the looks of it.

    Would the N249 not being connected be a possible cause of either the misfire or the charge pressure exceeded faults?

    I can't think of anything else, unless the map on the car is dodgy, but I have no way of knowing that. It definitely doesn't misfire at anything up to half throttle though. It can be quite severe too. I need to find the root cause of this issue. I feel like we are finally making some headway now.
     
  2. Advert Guest Advertisement


  3. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
    Staff Member Moderator Audi S3

    Joined:
    Sep 14, 2008
    Messages:
    20,281
    Likes Received:
    3,474
    The ECU needs to see something connected to the N249 plug else adaption and fuel trims won't work... this can lead to over fuelling on idle as the ECU won't compensate correctly


    The fact that you have misfires and open circuit fault codes on the injectors suggests this is related... I would be starting by tracking down your electrical gremlins before worrying about anything else... the codes are thrown for a reason... open circuit is effectively switching the injector off... injector off = no fuel, no fuel = misfire...


    Once you are fault code free then revisit the misfire issue but I suspect fixing the electrical gremkins will sort this out

    <tuffty/>
     
  4. JudderMan

    JudderMan Well-Known Member

    Joined:
    Nov 29, 2012
    Messages:
    1,003
    Likes Received:
    164
    But the N249 is usually at the front of the engine....or am I missing something here?
     
  5. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
    It isn't on the APY. It's nearer the top.
     
    JudderMan likes this.
  6. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
    Thanks Tufty, this is a nightmare!

    Actually, there is a fault for the N249 (obviously!) but there is also one listed as:

    17925 - Power Supply Relay for ECU (J271 or J363)
    P1517 - 35 - 10 - Electrical Malfunction - Intermittent

    I need to find out what that is and whether it's also related.
     
  7. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
    Really struggling to find out where this J271 relay is, or what the part number is to buy a replacement......

    I also can't find anything on ECP for an oil temp sensor, another item which threw a code.
     
  8. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
    Staff Member Moderator Audi S3

    Joined:
    Sep 14, 2008
    Messages:
    20,281
    Likes Received:
    3,474
    Engine control relay... its in the little black box on the passenger side of the bulkhead next to the trunking that goes into the scuttle..

    I still think you have wiring issues rather than loads of stuff actually wrong... have you checked the earths under the battery tray?

    I have a wiring diagram for an APY ECU... pm me...

    <tuffty/>
     
  9. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
  10. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
    I haven't yet checked those earths. Might be next weekend now. I can't see the one for the coils either.
     
  11. s3dave

    s3dave TFSI Hybrid
    Supporter

    Joined:
    Nov 11, 2009
    Messages:
    10,110
    Likes Received:
    736
    Also check the coil pack loom, they are well known to go brittle and crack the insulation off under the black tape, Awesome do a replacement loom for this and is well worth doing if in doubt..
     
  12. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
    Staff Member Moderator Audi S3

    Joined:
    Sep 14, 2008
    Messages:
    20,281
    Likes Received:
    3,474
    In this picture... the earth point is between cyls 1 and 2

    [​IMG]

    <tuffty/>
     
  13. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
    Does it include the earth? Any link at all?

    Tufty, almost certain that's missing.
     
  14. s3dave

    s3dave TFSI Hybrid
    Supporter

    Joined:
    Nov 11, 2009
    Messages:
    10,110
    Likes Received:
    736
  15. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
    Thanks Dave. It says that it's unsuitable for the 210bhp engine though.

    I presume my car does have an oil level sensor?
     
  16. vroomtshh

    vroomtshh Active Member
    VCDS Map User

    Joined:
    Jan 12, 2012
    Messages:
    362
    Likes Received:
    47
  17. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
    I might be being a dumbass, but I don't know if I have the oil level sensor? VCDS gave a code for an oil temp sensor at the last scan. Must therefore have one of those, but couldn't find one on ECP.

    Do you know of a loom for the APY engine?
     
  18. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
    Staff Member Moderator Audi S3

    Joined:
    Sep 14, 2008
    Messages:
    20,281
    Likes Received:
    3,474
    APY comes with an oil sensor in the sump... its used for temp and oil condition for AVS servicing

    As I have said to you on this and the other threads mate... your problems are not sensor related they are wiring related... you need to start tracking back the loom as there will be a common fault for all these sensors... a broken supply wire, earth or even the engine management relay...

    Don't buy any new sensors etc until you have tracked down your wiring gremlins... there are a few cars being broken in the classifieds and no doubt a few on eBay... see if you can grab a complete engine loom if its cheap enough

    <tuffty/>
     
  19. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
    Doh, yes I remember that now from having the sump off.

    Whole loom seems excessive but I think you're right and it's probably the best move.
     
  20. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
    Bought an APY engine loom. £60 posted. Fitting that will take some research!

    Not even sure where ECU etc are or exactly where all of the earth points are besides the ones I've recently been told about on here.
     
  21. vroomtshh

    vroomtshh Active Member
    VCDS Map User

    Joined:
    Jan 12, 2012
    Messages:
    362
    Likes Received:
    47
    ECU is under the scuttle panel.

    Earths are under the battery and on the gearbox mounting, plus some smaller ones dotted around
     
  22. Advert Guest Advertisement



    to hide this advert.
  23. Bad Sir Culation

    Joined:
    Nov 9, 2011
    Messages:
    287
    Likes Received:
    17
    Fitting the loom will be fun with very little clue!

    On a brighter note, since putting an N249 back on (just electrically) and putting some Redex in the car, the misfire seems to have gone!
     

Share This Page