Ph2 172 won't flicking rev'a in neutral

[Terrydb]

Hi guys I need some help my 172 when in neutral will flicker between 1500 and 2000 rpm it's never done this before it's fine when in gear I was told it could be the idle control valve but I believe I'm right in saying ph 2's don't have one if anyone can help it would be great thanks

terry

 

[MicKPM]

Correct, they don't have an IACV and the throttle plate acts to counter stalling (No, you cannot adjust this so don't try). Sounds more like you have an air leak somewhere on the inlet track or possibly another issue with something electrical.

Mick