Fast idling (2000rpm) after hot starting V8S

[Barkychoc]

Folks I've posted this in here cos I thought that it really doesn't apply just to the S.
If I park the car up, leave it a few minutes, then start it again it idles fast, did it today and sat at a steady 2000 rpm.
After a short bit of driving it settles down and never plays up at all while its running, only at initial hot start.

Engine is totally standard (if there is such a thing) 4 litre, 1992 pre cat.

Any ideas ?

Chris