VW 2.0 AQY Fast Idle?

[r.g.]

Hi,

I've just acquired a 2001 VW Beetle with the 2.0 AQY engine. When started from cold all seems good, idle settles ok, but after a minute or so the idle jumps up to 1500 to 1800 rpm. if you blip the throttle it will drop back to a normal idle, but a few seconds later will go back up to 1500. Idle is smooth with no misfire. It smells like its running rich. No CEL on, and I have read the codes with nothing showing. If I un plug the MAF, then there is no difference UNLESS I un-plug it after blipping the throttle before the idle jumps back up. then it maintains a low (slightly too low) idle until it's plugged back in.

Things I've checked:

1. Vacuum leak. Can't find anything, but it's hard to get in round the back of the engine where the throttle body is, although I can't hear anything obvious.
2. Cleaned MAF (doesn't always work I know)
3. Water temp sensor seems to be working OK. Reading correct temp and nothing when unplugged.
4. Cleaned throttle body. was pretty dirty in there. It's cable operated not FBW.

So, any suggestions? Could it be the MAF? I haven't checked voltage yet. what should it be reading?

Any suggestions would be much appreciated

[Mr2Mike]

Possibly the throttle position sensor. If this is getting intermittent the ECU won't know the throttle is in the idle position.

[r.g.]

The high speed idle isn't intermittent, it's happening all the time. The only time it doesn't is when first started or when the MAF is unplugged before it kicks in to high running.