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Black smoker - no faults found :( YET!

Discussion in 'A6/S6/Allroad forum (C6 Chassis)' started by Audime, Nov 2, 2012.

  1. Audime
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    Audime New Member

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    [Nov 2, 2012]
    Hi,
    I have a 2008 A6 C6 Avant 2.0 TDI 113k miles which is chucking out black smoke from stand still/pulling off.
    I cover 60 miles daily (pretty much and mainly motorway).
    Ran VAGCOM and found no faults.

    Checked four injectors and found no faults. They are also running within spec values (according to Vagcom measured values). SMIC and pipes have been checked for leaks and found none (by garage). EGR gate reported (by garage) to be clear, although not sure if it is chocked up. MAF reports well too.
    So far, I have given 2 hours labour to one garage who cannot find any faults, but agree that the car is giving out excessive black smoke when moving from Idle and are none the wiser. No loss in power though!
    I thought I might take the EGR off and see if it's blocked with carbon or not, but would that cause black smoke from the exhaust if it was blocked?

    Running out of ideas and car isnt very happy Please help.

    One other thing, Audi recently did a MOT and service. They changed the fuel pump (recommended). It was smoking a little from what I remember before Audi touched it, but the smoke does seem a little worse since they changed the fuel pump (I think).
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  3. Gunner Bill
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    Gunner Bill New Member

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    [Dec 18, 2012]
    Well you've probably fixed it by now (or got rid of the car) but it could be a split in the hosing on the intake side. I had this on a different turbo car and under acceleration it spewed out black smoke but was reasonably OK cruising. The split only opened up when teh engine flexed under load and took hours to find.
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  4. Audime
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    Audime New Member

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    [Dec 18, 2012]
    Hello! Actually, no still got it and still smoking like a tractor when pulling away.
    I took the intake hose off and had a good look at it last week. I can't say I found any splits.

    I really need to get it to another garage for a second opion! Need money and time. Neither I have :(
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  5. Gavin0478
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    Gavin0478 Active Member

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    [Dec 18, 2012]
    Are the fuel pressures too high as black smoke is usually over fueling??
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  6. Audime
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    Audime New Member

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    [Dec 18, 2012]
    Suppose I can check the pressure reading via vcds?
    But what do I compare the value too?
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  7. fisheggs
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    fisheggs New Member

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    [Dec 19, 2012]
    I know this sounds very obvious and basic. Replace your air filter.

    We once had a car that was diagnosed by a master tech as a blown turbo and I had the pleasure of rectifying the work. Turned out to be nothing more than a blocked air filter. Clouds of black smoke on acceleration and not fault codes logged.

    New filter and all was well. Even if you ave had the filter replaced, nothing wrong in pulling it out for an eyeball.
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  8. Audime
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    Audime New Member

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    [Dec 19, 2012]

    Thanks for the suggestion too, but I have already changed the air filter along with a new MAF to no avail, £120 down the pan better spent on a real car engineer.

    Trying to learn about fuel pressure regulators now to see if that's playing up. Woohoo!
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  9. SL11CKK
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    SL11CKK Active Member

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    [Dec 19, 2012]
    Check how the intercooler is. Any signs of oily soot around that area. Check through the grill.
    #8
  10. Audime
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    Audime New Member

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    [Dec 24, 2012]
    I did have a garage pressure test that and it was ok apparently. Perhaps a proper visual inspection is needed! I cant seem to see the SMIC through the grill. Guess if I take the bumper off I can get to it easy? or better on a ramp?
    #9
  11. gupsterg
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    gupsterg Active Member

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  12. Audime
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    Audime New Member

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    [Aug 6, 2013]
    Electrical fault with EGR valve. Gate stuck open (or closed I can't remember)
    #11
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