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Audi A6 C7 CNHA - Smoke Issue

Glen Douglas Nov 27, 2019

  1. Glen Douglas

    Glen Douglas New Member

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    Hi all,

    Looking for a bit of advice on a tricky situation on a 2015 Audi C7 A6 Ultra with a CNHA engine. I'm an independent garage, the customer who is also a friend has brought his Audi A6 into myself bit of a back story on this car.

    The car's DPF failed 3 months into ownership for the customer (previous owner likely doing short drives) customer took the car to an Audi specialist in the Glasgow area who suggested the cheapest option would be to remove the DPF/hollow the DPF out and map the EGR out which the customer done (Not my suggestion obviously) however understandable given Audi were looking for the best part of £4,000+ to replace the system. Car was mapped using a map by a Celtic Tuning vendor and customer reported that the difference in performance was night and day .. for around 3 months, customer reported that the performance of the engine slowly got worse to the point now it's been sitting in my garage essentially unable to drive.

    The problem is we can't work out what is causing the problem, I've had the DPF and EGR off the car as they are one unit to inspect, there was massive amounts of carbon buildup on the EGR cooler however I noticed that the company in question have essentially custom made a blanking plate over the EGR to prevent flow through the cooler hence is should essentially just be free flowing so this ruled the EGR/DPF out as a problem.

    Essentially the symptoms are, thick black smoke on idle to the point we have to turn the car off after 20 seconds as the garage is filled with the stuff, extremely rough idle, almost little to no power, we are also getting some diesel cracking/knocking.

    The puzzling bit is the car had these exact same symptoms prior to the Celtic tuning map and the map seemed to resolve the issue so I'm left wondering if there is anything else we can check?

    Is it possible that the car's ECU has reverted back to a factory map setting automatically? I know the new RS models are known for this but I wasn't sure if this was the case for the 15 plate non RS models.

    I have spoken to another Audi specialist who has advised to check the inter cooler for damage but again I'm not confident this will resolve the issue.

    As far as codes go - We are pulling up EGR excessive flow & P0671 - Cylinder 1 Glow Plug circuit (Plugs were changed 3 months ago)

    Cheers
     
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  3. EXSpartan36

    EXSpartan36 Active Member VCDS Map User Team Phantom S-line owners group saloon TDi Audi A4 Manual

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    Thick black smoke is normally caused by too much fuel or Not enough air so I would be looking at the intake system for any cracks or splits in pipes especially around the intercooler. There is a really handy tool that pumps smoke into the intake which shows leaks really easily. If that is all ok you can test the injection quantity deviation of the fuel injectors with VCDS which should give you an idea if you have a faulty injector.
     
  4. bobby singh

    bobby singh BSR Gold Supporter VCDS Map User TDi quattro Audi A4

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    Reset the DPF soot adaption - maybe the DPF off in the file hasn't been done correctly.
    If the smoke stops then you know.
    However, DPF regen smoke is normally white ish (fuel)
    Black smoke could be bad injector especially on idle as massive boost leak shouldn't matter on tick over.
     
  5. luci

    luci New Member

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    Hi Glen,

    I have a similar issue with my audi a4 b8.5 quattro stronic 2.0 tdi 190 cnha
    the black smoke that is giving me headaches for the last months
    initially after purchase, at around 100.000km the adblue got errors and also started eating coolant. rather than fixing it, i chose to disable the adblue. so i did a dpf off (both filters properly emptied) adblue off stage 1 software with my car. after this i got white smoke because of the coolant, i figured the problem was with the cylinder head gasket, which is common for this engine, so i changed it. after this all was ok for a while, no smoke. then it all started. this black smoke i cannot get rid off. mostly when i accelerate. on tests it says engine does not have enough boost so the smoke is unburned diesel.egr was on at this moment and also stated malfunctioning so i did an egr off as well. no change.
    i checked all the pipes to see if there is no pressure lost, nope. i replaced the injectors, nothing. new admission gallery, still nothing. washed the intercooler, no change.

    if you figure out what's wrong let me know as i am still looking for a solution.
    as far as i know i am not the only one with this issue, but this is the only thread i found related.

    possible things for you to check: admission gallery buildup; the upper intercooler properly cleaned and washed; being shure that the dpf off was done properly meaning full removal of the filters; egr valve stuck. and of course egr buildup.
     
  6. bobby singh

    bobby singh BSR Gold Supporter VCDS Map User TDi quattro Audi A4

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    Maybe the tune you have is smokey? try a map with just egr and dpf off.
    Also, block the egr with a plate
     
  7. luci

    luci New Member

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    Egr is still mecanically closed after a 5000km inspection as seen in the picture... the remap was remade it is now close to stock... i would bet on a generic issue with something as i am not the only one affected, there are other cases of this smoke issue with the cnha engine. The mechanics still cannot figure out the problem.
     

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