Audi S3 - 10 plate. Engine intermittent idle speed?

[Jdavis12]

Hello, new on here.

When engine is cold it idles ok, but when hot and sitting on drive I get intermittent idle from 800/to 1700 rpm and this creates soot deposits from exhaust.

Any helpful suggestions please before I spend unnecessary money?

Many thanks,
Jason.

(also, desperately seeking a crisp, Mk2 Escort RS2000 in Signal Yellow to recapture lost youth....!)

[si_xsi]

Diverter valve or Mass air flow meter? Might be worth plugging into Vagcom to see if an faults come up.

[Jdavis12]

Hi we did a smoke test and found fault with PCV valve.Removed head and found that diaphragm was split replaced the part all ok now idle is back to normal