Mk1 high idle revs

hi, having problems with a high idle, from startup car will idle at around 2000 revs and will stay at this idle even when up to operating temp..

when throttle is opened it will rev up then down but then return to original 2000 rev idle.

car idles smoothly, starts first time - CHECKED throttle switch, coolant temp sensor, air flow meter and aux air valve.

any thoughts please..

Vaucuum hose from plenum to servo ???

Thanks for suggestion, had a feeling it might be a vacuum leak problem

Have changed original brake servo and master cylinder for a punto gt one, do u think this could be causing it

 wondered if someone had experienced the same issue.

coltuno wrote:Thanks for suggestion, had a feeling it might be a vacuum leak problem

Have changed original brake servo and master cylinder for a punto gt one, do u think this could be causing it

 wondered if someone had experienced the same issue.

If you have had this problem since fitting it, check that the one way valve is operating correctly...

I had a fast idle issue on my original UT back in the day and after checking everything I could think of my father-in-law diagnosed it (by squirting water on various parts of the engine while it was running) as a leaking inlet manifold gasket. It was only very slight but enough to lift the revs to about 1300rpm. Might be worth you doing a similar check on yours?

One of these homemade gadgets is ace for checking boost and vacuum leaks 

Thanks for the input guys, i am going to check all vacuum hoses and the brake servo vacuum joint with the engine running, inlet manifold gasket is new and all nuts are tight in that area, so doubt that is the problem, but will check..

Any more info on that gadget charlie, and how you use it..

how did you get on fitting the pgt servo and master cylinder?

It fits in the AFM pipe pressuring the whole system with air.. Any leaks in the inlet, injector seals, boost pipes etc, etc are easily found by the hiss. I had a leaking auxiliary air valve pipe under the jubilee clip at 5psi that I would never of found without this

-the punto servo and master cylinder fit in ok, but where the brake arm inside the car fixes to the servo pushrod it doesnt correctly line up so u either space the servo from the car body using a bracket or alter the position of the pin on the brake arm. (Slutters had guide on old site)

Brake piping also has to be slightly altered.

-That gadget looks like a good system will probably end up trying this method - thanks for that..

an update! - found vacuum leak after a considerable amount of grief, turned out to be a leak where vacuum hose joins brake servo on the rubber seal..

coltuno wrote:an update! - found vacuum leak after a considerable amount of grief, turned out to be a leak where vacuum hose joins brake servo on the rubber seal..

Ah great, glad i pointed you in the right area, often overlooked for what seems a be a head scratcher when all looks well...

yeah, should have checked it first..