s3 idling funny

[c6dsy]

My s3 started idling weird tonight i drove about 8 miles and then was out car talking to someone then jumped in the turn round and noticed revs dropped down really slow then changing gear was getting backfire once home i took it out of gear and let it idle and its fluctuating between 2000 rpm and just below 1000rpm going up and down and if i rev it there is a back fire too any ideas? Got an ig maxogen fitted and full miltek turbo back exhaust

 

[mjr901]

My s3 started idling weird tonight i drove about 8 miles and then was out car talking to someone then jumped in the turn round and noticed revs dropped down really slow then changing gear was getting backfire once home i took it out of gear and let it idle and its fluctuating between 2000 rpm and just below 1000rpm going up and down and if i rev it there is a back fire too any ideas? Got an ig maxogen fitted and full miltek turbo back exhaust

you could try cleaning the MAF.

 

[c6dsy]

where is it? and clean it with what?

 

[MrLapou]

Vacuum leak. Oil filler cap seal leak.

 

[c6dsy]

Vacuum leak. Oil filler cap seal leak.

Cant seem to find any leaks but when I turn it off the circular plastic bit on front of rocker cover hisses away for a bit maybe 15 seconds it has a small hole that is meant to be there that's where air is coming from

 

[170sam]

PVC valve common fault

 

[c6dsy]

PVC valve common fault

just replace that then see how it goes?

 

[170sam]

My bad pcv valve

 

[170sam]

Yea replace it I'm sure it will fix your issue

 

[170sam]

Yea just replace it and I'm sure it will fix your issue for you .

 

[MrLapou]

Try taking cover off with engine running to see what happens.

 

[c6dsy]

Try taking cover off with engine running to see what happens.

if i take oil cap off it runs worse then air hisses out valve at front i will try pcv valve

 

[jaydav2306]

What is a PCV valve and what does it do????

 

[c6dsy]

What is a PCV valve and what does it do????

Its a valve on the front of rocker cover that takes breathers from block and inlet manifold and has a diaphragm in it to alow them all to breath, seems if diaphragm breaks air leaks straight to inlet causing idle to fluctuate

 

[jaydav2306]

Is this the thing located on the top left hand corner above the oil cap? Good to know