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  1. #1
    1998 A4 B5 1.9TDI (AFN)

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    Boost/Smoke/Rev issues, PLEASE HELP!!

    Hi guys

    I wonder if any of you can help me......

    I've developed some kind of fault on my Audi A4 Avant, it's a 1.9 TDI 110 (AFN).

    It revs on it's own on startup, smokes quite a lot when it starts, but this then disappears, and I appear to have a complete lack of boost...!

    There seems to be boost at low RPM, and I can hear the turbo doing its thing, but when I should get a massive boost, it's like it's not there and the wastegate is all the way open.

    I stupidly consulted the Haynes book, their diagnosis is possible injector fault although it runs ok, doesn't sound like it's only running on 3, and fires all the way through the range, just seems to have no boost!

    I have suffered with overboost before, but this is different, an switch off/switch on doesn't work! All the hoses are present and correct, and none of them have any holes in.

    I'm totally at my wits end, and I REALLY need the car working properly!

    Any advice would be most helpful thanks everyone!

    Chris

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  3. #2
    "Stick a V8 in it!"

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    What color is the startup smoke?

    It could be oil leaking into the cylinders, from the valve guides or turbo, and its something to be careful with because if enough oil gets in it can cause the engine to run away and destroy itself.

    The lack of boost could be a stuck VVT actuator or a big leak?

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
    2000 A4 1.8T Sport Quattro Saloon, Black-ish
    1997 S4 - PPC £999 Challenge Track Car Build
    TD5 Land Rover Defender build


  4. #3
    1998 A4 B5 1.9TDI (AFN)

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    Hi, thanks for replying!

    It's like a grey smoke, like there's too much fuel. It doesn't smell oily (although it bloody stinks), and the oil level is good. When it revs on startup, it goes up to 2000rpm then drops back to normal idle speed. I've had a chat with a few people and it seems to be pointing to the charge pressure sensor. I disconnected and took it out, and it didn't make any difference, then thought 'Doh! Now there's a hole in the boost system, idiot...' so put it back in but didn't connect it, still no difference.

    I've checked all the turbo hoses and there doesn't seem to be a leak, quite the opposite in fact, they all expand as they should when the turbo spins, it's now almost like the sensor isn't reading the charge pressure and therefore not telling the ECU to dump more fuel in to cope with the extra air from the turbo.

    Does this seem like a plausible fault? I'm loath to go spending out on parts until I'm absolutely sure of what the problem is and what I'm going to need to fix it. I have a friend with a VAG lead and software, but finding a time for both of us to be free is proving somewhat difficult!

    Cheers!

    Chris

  5. #4
    "Stick a V8 in it!"

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    Get a cheap vagcom lead from ebay and scan it for codes.

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
    2000 A4 1.8T Sport Quattro Saloon, Black-ish
    1997 S4 - PPC £999 Challenge Track Car Build
    TD5 Land Rover Defender build


  6. #5
    5th Gear

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    I`m only an hour from you if you need it scanned at weekend, near Norfolk/Suffolk border.( Loddon) .Or if you want to come to a localish meet on the 18th Dec at the Tivetshal ram on the A140 near Diss can do it then?l

  7. #6
    1998 A4 B5 1.9TDI (AFN)

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    Sudbury, Suffolk
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    Hi guys

    Thanks for all your replies!

    Finally arranged something with my local man with VAGCOM, scanned, came up with codes for intake pressure sensor etc etc, then decided to run on 3 instead of 4... Codes cleared.

    Found a hose that goes to the air box was off... Put this back on, test driven, and I appear to have my BahnStormer back!

    Unsure as to whether it was the codes being cleared, or the hose put back on that cured it, or maybe both, but if it happens again, I'll let you all know.

    Could be worth bearing in mind in case you guys have the same kind of troubles!

    Cheers!

    Chris

 

 

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