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

[quattro25years]

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.

 

[DGSdale]

Clean your throttle body & butterfly. Had the same problem myself. This is a very useful link from Audiworld.com
http://www.audiworld.com/tech/eng.html

 

[matt_o121]

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

 

[auroan]

Idle control valve i'll put money one it !

Sits at the back of the engine block below the throttle body.

 

[matt_o121]

guess it depends how old the 2.8 is - 12v have idle control valves
30v dont