450 Revving / Idle Problem

[1BigBadWedger]

My 450SE has developed a strange idle problem where it revs at 1500-2000rpm when it's in neutral but when I come to a standstill it eventually settles down after 10-20 seconds to the usual 1000rpm. I've also noticed going through town at 30 mph can be tricky as it's trying to rev more. If you pull over though it soon settles down.

I've checked the throttle cable and it's not that and I've cleaned the end of the stepper motor so I am thinking it might be a temperature sensor problem.

Any thoughts or ideas would be great!

Cheers
Nick

[honestjohntoo]

I does sound a bit like "Idle Speed Hang-up" due to the throttle plate not fully receding when the throttle is closed

Then, when the engine is idling the vibrating engine helps the plate and its mechanism to overcome any local friction and the plate slowly closes.

Loadsa help and clues here:

http://www.vintagemodelairplane.com/pages/Download...

Just transpose all the principles therein to a single plenum system.