Ola! Joe, the idle control unit is located behind the right rear tail light
(passenger side) you must remove the tail light assembly to access it (4
screws).  It is a small black box mounted to the sheetmetal inside that
cavity.  There is good info in the archives on a capacitor replacement in
that unit.  I have done the capacitor fix and it cost under $10 versus the
replacement of the entire unit which is well over $100.  My suggestion is to
search the archives on this topic.
!Salud!
Loretta
87 Syncro
90 GL
82 Westy