In a message dated 2/1/05 7:17:46 PM, craigoda@GMAIL.COM writes:

<< I would check the aux air valve first.  I have a 83 and am not sure
where this valve is on a 90. >>

It ain't.

Dave, first check the Temp II sensor for correct response, its termination
for security and its wiring for continuity.  If all that is kosher, then
methodically go through the Idle Stabiliser System.  Should you not have a Bentley
manual, now is the time to spring for one.  And, when wading through that morass
some call the Archives, take care to only change parts VERIFIED as defective.

George