Very high idling on my 172.

[SuperJ]

It's only started today but the idle is very high on my 172. Around 3k revs. What could be the most common causes?

 

[OliRose1994]

Take your foot off the accelerator ... Nah, just kidding. I was going to suggest it being the choke, as the weather's doing a little bit of a crazy turn at the moment and getting cold overnight, but I don't think a choke would rev your engine that high. If it's not that, then I'm stumped .

 

[Bluebeard]

a failed gasket on the inlet manifold i'd suggest. Or the rubber o ring at the back under the it has gone crusty and fallen out.

Start with the cheapest solutions first!

 

[Snake182]

This car wont have a choke ( in reply to an above comment) it will have a fast idle speed for a cold engine but this will drop when the engine warms up. Check for air leaks around the inlet manifold, i.e brake servo pipe, map sensor fitted correctly. Also try cleaning the throttle body to start with.