88 5K ISV (non-turbo)

["Christopher Ritchie" <cjr1@gte.net>]

Cleaned the ISV with carburetor cleaner.  Moves nice and free.  However,
most of the time the idle is still at 1200 rpm.  Sometimes will drop to
~900.  This is at operating temperature, no A/C, ordinary electrical load. 
What else to check?  What is the electrical check for the ISV?  Cannot find
any vacuum leaks.  However, removing oil filler cap and/or dipstick while
the engine is running has no effect on idle.