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2008 a4 2.0tdi cab misfire

s3_stu_260 Jun 21, 2012

  1. s3_stu_260

    s3_stu_260 New Member

    hi guys
    any advice on what might be wrong with my car would be much appreciated
    to start at the beginning
    car = 2008 "58" audi a4 2.0 tdi cab engine code BPW less than 50k miles
    faults :-
    1, DPF light on dash, loss of power ( dpf removed and software adapted to allow for this)
    2, misfire ( there has been no good period between dpf issue and misfire)

    work done so far :-
    1, diagnostics with vag.com ( no fault codes )
    2, all 4 injectors removed and tested by specialist with no faults found ( replaced with new seals )
    3, live data showed no.4 injector to be considerably different to other 3
    4, injectors swapped no.1 & no.4, problem still at no.4
    5, wiring loom for injectors replaced
    6, compression test showed all equal and good
    7, egr valve removed and checked ( all working when compared to a new one )

    the injectors have been installed and set as per autodata
    please if i have missed something or you have any thoughts on the matter as its doing my head in
  2. murran

    murran Well-Known Member

    well from what youve said your problem obviously lies with cyl.4. the comparison reading being out. how out was it? what were the figures?

    and the compression test was all ok and even across all cylinders? even 40 psi lower in one cylinder will cause problems.

    you say youve swapped injector 4 and 1 around? and the "out" comparison figure stayed at cyl. 4?
  3. s3_stu_260

    s3_stu_260 New Member

    yes compression showed the same across all 4 cylinders
    the problem lies with cylinder 4 as which ever injector you put in no4 shows on live data being vastly different to other 3.
    i have removed vacuum pump from end of head to check fuel line, when its back together i'll get figures
  4. murran

    murran Well-Known Member

    the comparison figures are meerly the ecu trying to balance out variations in the power created in each cylinder. ie; say all cylinders were equally down on power the comparisons wouldnt look out. but one cylinder down on power youd see a minus figure for example...
    1) 0.9
    2) 1.4
    3) 1.1
    4) -2.8

    have you double checked the compressions? how are you checking them?
    should be roughly 80-100 psi on the first and 340/360psi after 8 cranks.

    if this checks out id go back to whoever mapped out the dpf for you, get them to look at it.

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