Filled car with momentum99 drove 20miles and now car has started idiling funny(sounds as if car is going to stall) then every now and again revs increase on there own to around 2k. Power is also down, feels like a 1.2.

Car is a skoda octavia vrs 2.0t 101k there is no engine light on.

Edited 6 March, 201115 yr by donovan

bump

What's causing it, air, spark or fuel?

Revs increasing is normally air related. Vac leak? Throttle gummed up? Dodgy throttle position sensor?

Id hook it up to Vagcom / Vcds. If theres no fault codes then live data makes short work of pointing out problems.

Good mechanic?

Check all the vac hoses in the engine bay and give the throttle body a good clean with carb cleaner.

Revs suddenly increasing is normally an air leak somewhere. You can spray round the intake manifold gasket and other areas with the engine running with carb cleaner - if the engine speed fluctuates when you spray a particular area it is drawing in air there. Don't use WD40 as it will damage your cat.

Could be a dodgy MAF - as above - get it scanned somewhere.