My daughters 1997 Rev 4 n/a has started to hunt on idle between 1500- 2000 rpm, it wont idle at 900 rpm as it used to.

I have checked for vacuum leaks but cant see any

.

I have pulled off a few pipes to see if there are any changes but the only thing that makes a difference is when I pull the small rubber

vacuum pipes off the light green sensor fitted in the inlet manifold plenum just after the throttle housing

-

(it runs rough but stops hunting

)

.

The car just idles now at 1500 to 2000 up and down continuously

, this fault just suddenly appeared on a drive home from work

.

Any advice greatly appreciated

,thanks in advance

.

Thank you members

, car now fixed.

As advised I cleaned the Idle stabilisation valve and now all is well

.

To do this I removed the throttle body to gain access to the two cross head screws holding the ISV

.I removed the solenoid housing and cleaned the inside plus the plunger and worked it through 90 degrees whilst adding a light spray of 3M 5 way spray then wiping clean again.

I did not remove the

coolant hoses from the throttle body as I did'nt want to disturb the cooling system etc.I replaced the two cross head screws with stainless allen screws.

When I started the car up I knew straight away that all was well due to it being far smoother on tick over although I had to adjust the idle screw ever so slightly to get an 850rpm tick over from around 650 rpm

.The car sounds very sweet now

, thanks once again.
