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IDLE SPEED TROUBLE---hunts to find correct tick over speed

Discussion in 'A6/S6/Allroad forum (C5 Chassis)' started by quattro25years, Apr 25, 2009.

  1. quattro25years
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    quattro25years Member

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    [Apr 25, 2009]
    hi all

    i have a a6 2.8 quattro.

    whenever i stop at a junction for example, sometimes the engine cuts out or has to hunt for the correct tickover speed (this happens about 7 times out of 10).

    (once engine has cut out -- start up again and its ok),

    the problem above only seems to happen once i have driven the vehicle(any distance).

    if i just start the engine from cold , the tick over speed is perfect)

    any ideas ??

    cheers

    quattro25years.
    #1
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  3. DGSdale
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    DGSdale Member

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    [Apr 25, 2009]
    #2
  4. matt_o121
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    matt_o121 2.8Q

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    [Apr 29, 2009]
    if cleaning the throttle body doesn't work - ( a good starting point)

    you could try the charcoal canister - i had problems with the vent to atmosphere being blocked - it comes out under the floor by the drivers door - a black pipe that goes in to the driver wheel arch.

    or the evap control valve - on top of the air filter under the plastic trim. there is a plug going to the valve - if you disconnect it the engine will run still - see if it makes any difference - doesnt put a dash light on but will log a fault in the memory.

    mine was sticking and when hot stayed open allowing un metered air in to the inlet causing hunting and low rpm at idle
    #3
  5. auroan
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    auroan Active Member

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    [Apr 29, 2009]
    Idle control valve i'll put money one it !

    Sits at the back of the engine block below the throttle body.
    #4
  6. matt_o121
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    matt_o121 2.8Q

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    [Apr 29, 2009]
    guess it depends how old the 2.8 is - 12v have idle control valves
    30v dont
    #5

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