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  1. #1
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    Starting issues and flap valve??

    Engine management light has come on. Noticed last few weeks car doesn't want to start early mornings, never been an issue before. When running it seems to run rich, strong smell of diesel from rear of car. Ecu fault code was intermittent flap valve fault? We are assuming this is the flap in the throttle body? I've taken the intake off cleaned everything out. When i exposed the throttle body i noticed the flap was in the open position, is that right? I always thought they opened with acceleration to allow more air intake? Recently had new egr valve, cooler and solenoid. Once the car is warm it will start first time all day long until the next morning. When it does finally start there is a load of smoke from exhaust for first couple of seconds?

    Any ideas what's going on guys? Cheers

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  3. #2
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    Engine info would be useful but as your in the diesel section, I'll asssume that for starters. Diesels don't have a throttle body...acceleration is controled by the amount of fuel injected by the injectors.

    The flap valve you mention will be the anti-shudder valve (part of the EGR) which only operates when you turn the engine off to prevent excessive vibration so will be open at all other times. If it's recently been replaced then I would check the vacuum hose connection and the integrity of the actuator arm. The anti-shudder is the one with the black plastic actuator, not the big silver one. This is the EGR actuator.

    If the flap valve is operating intermittantly then it will be starving the engine of air which means the fuel being injected won't be completely burnt. This would relate to your rich running issue. When the engine is turned off, this excess fuel will pool in the combustion chamber giving you the cold start issue.

    My money is on a flapping flap valve
    A4 Avant 1.9 TDi Sport GmbH

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    Cheers mate. It's a 1.9tdi 115. Sounds like you've hit the nail bang on there, makes sense as to what's happening with my car. Not sure where the actuator is located? Don't know what i have been looking at, I thought it was a throttle body type thing? I removed the thick air hose from top/back of the engine and that's what it was fastened to. Has a rotating flap but its stuck open.

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    Is the actuator bolted to the turbo?

  6. #5
    Audi Doodah's Avatar
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    An EGR valve. It has two functions, the main one being to pass exhaust gasses back into the intake to reduce emissions. The other being the anti-shudder. The actuator for the anti-shudder valve is the black one at the bottom of this picture (EGR diaphragm is the silver part at the top). As it's made of plastic it's quite possible it's damaged and flapping about when it shouldn't be. As I said, this flap will ONLY close when you turn the engine off and the re-open when the engine has stopped.

    There is also an actuator on the turbo but this is to control boost pressure by changing the angle of the vanes within the turbo.
    A4 Avant 1.9 TDi Sport GmbH

 

 

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