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Help me cure a random miss fire/rough tick over on idle please.

Discussion in 'A3/S3/Sportback (8P Chassis)' started by AidenUK, Feb 12, 2012.

  1. AidenUK
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    AidenUK Well-Known Member

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    [Feb 12, 2012]
    I'm almost at my wits end with this now, my car has been suffering from this for months.

    When you cold start the car it starts and runs perfect, if you get the car up to temperature then that's when this rough idle/misfire intermittently occurs. I can pop the bonnet and you can hear and see the engine shaking/missing.

    When cold and warm the car drives perfect but just to give you an example of when this happens, I'll be coming back from Wakefield on the M1/M62/M606, I'll get the end of the 606 and waiting at the lights on the slip road and it will start to shake and miss, once I set off its perfect again, the car drives perfect whether hot or cold but only idles rough when warm.

    I have replaced the injector seals, replaced the fuel filter and temporarily blanked off the EGR valve, timing is correct, injectors have been checking in VCDS to see if they are firing correctly and the car still does it!

    What else is there to try now? The car is throwing NO errors up on the ECU, I wish it would but it's not. I'm getting close to taking a can of petrol and a newspaper to it.

    The car is a 2.0L TDI 140, manual, 57K.

    What can I try now? Please help.
    Last edited: Feb 12, 2012
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  3. tdi-man
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    tdi-man Well-Known Member

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    [Feb 12, 2012]
    need to make sure timing is 100% set up by some one that knows what there doing .

    also fueling on idle might be low so will need to be mapped to turn the fuel up on idle .
    #2
  4. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 12, 2012]
    You need to record the blocks when its doing it with VCDS. Ideally you need someone who knows what they are doing in the passenger seat with their lap top to read the live data while the fault occurs. this will enable you to see which cylinder is not firing or losing compression etc or if its multiple cylinders. It should also show if there is any imbalance in the data which will point you in the right direction.
    #3
  5. AidenUK
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    AidenUK Well-Known Member

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    [Feb 12, 2012]
    The timing is spot on mate, forgot to say that it's just had it's cambelt changed, the lad that's done it used to work at VW Crosshills near Skipton in West Yorkshire.

    I don't want to remap the car as i don't want to pop the turbo, surely this isn't the only solution? I can up the idle if needs be as a good chap on here named Mike Foster would do this for me (Thanks Mike :beerchug:..)
    #4
  6. AidenUK
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    AidenUK Well-Known Member

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    [Feb 12, 2012]
    These have been checked and are firing correctly Paddy (so i'm told anyway).
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  7. Charlie Ford
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    Charlie Ford Member

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    [Feb 12, 2012]
    The timing only needs to be out ever so slightly to have this issue I spoke to the stealer tech and mine does the same and is slightly out and was timed by an Audi specialist
    #6
  8. AidenUK
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    AidenUK Well-Known Member

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    [Feb 12, 2012]
    It did this before the cambelt change and hasn't improved after it. The timing is correct pal.
    #7
  9. AidenUK
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    AidenUK Well-Known Member

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    [Feb 12, 2012]
    Probably a noobish question but would a faulty DMF cause a missfire or just a violent shake?
    #8
  10. mike foster
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    mike foster Fossie VCDS Map User

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    [Feb 12, 2012]
    Aiden - will up the tickover with pleasure but one thing that has cropped up in the past and which does not show up on VCDS is the injector wiring loom breaking down internally under load. For some reason or other this seems to be worse when stationary on an incline.

    £82 for a new one !
    #9
  11. AidenUK
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    AidenUK Well-Known Member

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    [Feb 12, 2012]
    That would explain why it's worse on incline mate, I'll have suggest this to the mechanic on Monday when he un blanks my EGR valve.

    So it's 82 for the loom only Mike?
    #10
  12. mike foster
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    mike foster Fossie VCDS Map User

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    [Feb 12, 2012]
    Yes - £82 including VAT from Audi.

    I'll get you the part number if you give me the year

    Edit : don't need the year it's 03G 971 033 L
    Last edited: Feb 12, 2012
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  13. AidenUK
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    AidenUK Well-Known Member

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    [Feb 12, 2012]
    Have you had yours changed on yours Mike?
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  14. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 12, 2012]
    Wasnt the loom a recall issue Mike ?
    #13
  15. mike foster
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    mike foster Fossie VCDS Map User

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    [Feb 12, 2012]
    No - doesn't need it although sometimes it vibrates a bit.
    #14
  16. mike foster
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    mike foster Fossie VCDS Map User

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    [Feb 12, 2012]
    Not sure Paddy - not like the injector issue with the 170 !
    #15
  17. AidenUK
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    AidenUK Well-Known Member

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    [Feb 12, 2012]
    Does it actually missfire or just vibrate though Mike?

    Mine missfires, you can hear the engine knocking!

    Can of petrol is coming out soon.
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  18. mike foster
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    mike foster Fossie VCDS Map User

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    [Feb 12, 2012]
    Just shakes a bit sometimes - no apparent misfire.

    You could try petrol but I wouldn't really recommend it !!!!!!!!!!! lol
    #17
  19. AidenUK
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    AidenUK Well-Known Member

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    [Feb 13, 2012]
    UPDATE: Mike has lowered the idle limit to 800rpm and it's been perfect since (touching wood as i say this as i don't want to jinx it).

    Thanks again Mike!
    #18

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