V40 hunting for revs

[JUDGENINJA]

V40 is playing up already... driving is fine, car goes like stink and embaressed a few cars...then ever so often the car is embarrassing me.

Sitting at idle the car drops revs as if it wants to stall, then picks up all of a sudden with the idle control valve. RT's showed no specific fault code.
I've wound the throttle cable in a bit to help, but it must just wind itself as after 10mins it is back to hunting.

The changes are 850 single mass flywheel from a dual mass one. We had wondered if the RPM sensor in the V40 need swapping for the one from the 850??
Any other ideas?

[stribo]

I would say either the ICV needs cleaning, or the MAF could be playing up, just unplug each one in turn when the car starts hunting.

[JUDGENINJA]

MAF has been unplugged already... maybe try the ICV to see what it does..

[V70 Graham]

Hope the problem is easily found/sorted mate.