S3 slightly rough idle

[Colly]

My car seems to have developed as slight fluctuation in idle, and a slight his/whistle on boost I take its most probably an air leak anyone got any ideas?

 

[Customboy]

Just check all ur hoses for leaks round turbo and under and around manifold mate, year of the car and spec or mods do e may help mate

 

[Colly]

Thanks ill have a check tomorrow is there some more common to go than others? The car is oem

 

[Colly]

bump can anyone one help?

 

[<tuffty/>]

Check the pipes under the inlet manifold...

<tuffty/>

 

[s33nyboy12]

Mines currently running very slightly rough idle, but with bit of spongy brake travel. Got it booked in at the weekend at vag specialist to check it out on phone they mentioned brake vacuum pipe?????......

 

[Colly]

Surely this would have nothing to do with the idle tho?

 

[<tuffty/>]

Surely this would have nothing to do with the idle tho?

If the servo vac pipe has a split (which can happen) then yes it can affect idle... its drawing in air that the ECU can't see so the mixture leans out and the ECU adjusts by adding more fuel... the ECU also regulates the throttle plate to keep the idle steady but is fighting the air leak so makes bigger adjustments than usual and the idle ends up being all over the place..

<tuffty/>

 

[Colly]

thanks worth a look where is it located?

 

[<tuffty/>]

On the S3 the servo vac pipe starts from the end of the pipe circled red (bottom left) off the pic above and runs past the power steering reservoir and expansion tank to the servo on the bulk head... the check valve is wrapped in a piece of heat resistant fibre glass behind the aluminium heat shield

<tuffty/>

 

[<tuffty/>]

...should mention its not normal for them to go wrong on the S3... A3's suffer from this issue more... most air leaks are from the pipes under the inlet as mentioned before and shown in the pic above...

<tuffty/>

 

[willh92]

Sorry to revive an old thread, but was doing some research as my S3 suffers from slightly rough idle. Also, when i start it up if it's already hot and been left standing switched off for about 30-45 mins it will start up fine but try to idle and cut out almost straight away every time unless i give it some throttle.

Could any of the above be related to an air leak on the pipes in the above pic maybe?

Car has done 79000 miles with full Audi history and cambelt change at 76000 miles. It is a T reg, if that matters?

Cheers.

Will

 

[Dani_B19]

What fault codes does it show?

 

[willh92]

well i havent had it scanned yet, was hoping to get away without doing so if someone had any ideas to give a go first on here.