Tech question on HGT

[Ian]

I have a 155 HGT and it idles quite high, around 1200rpm on the rev counter. It used to idle around 800. Driving is fine but when you stop the revs never go below 1200, (well occasionally down to 1000). Now when you roll forward the revs rise up to 1500 or higher but if you put the clutch in and roll forward the revs stay around 1200

Does anyone have any ideas what could be causing this? I had it diagnostic checked when the cambelt was done recently and the guy said there were no problems coming up. Could it be the MAF which people have been talking about recently or is more likely something to do with the actual throttle?

Answers on the back of a post card please

 

[Steve]

try the trottle position sensor

or the idle speed controler

 

[Ian]

I believe the idle speed controller is built into the throttle as it is a Mk2 engine. Where would I find the throttle position sensor? I had the throttle potentiometer changed but that made no difference

 

[Tom]

The MAF does very little at idle as the air flow is so low.

My guess is its a sticky throttle body. The fly by wire throttle body on the Mk2 HGT is stupidly overly complex.

 

[Ian]

I did not think it would be the air flow as it even does it reverse, if freewheeling with no clutch revs rise if depress clutch revs drop.

Is there anything I can do if it is a sticky throttle? I know the throttle is way to complex and hard to get to. If it was a Mk1 would be easier