Mk 1 focus idle issue

[Makem]

I have a 99 ford focus. Starts fine when cold and idles ok. Then drive to first junction, dip the clutch and the revs hang at 1400 until i pull away again. Does not do this once warm. Have changed the throttle position sensor, no difference. No error codes at dealer. At a lost really, anyone had anything similar. Thanks in advance.