1994 Volvo 850 wagon - std fuel injected engine - manual shift.
Normal idle is 850 RPM.  Usually very steady.
When coming to a stop, I usually depress clutch and downshift,
maintaing clutch depressed.  Randomly, idle keeps dropping
past normal 850, sometimes recovers, sometimes goes to zero
(i.e. car stalls).  No problem restarting.  Any ideas?  Is there
an idle stabilizer/injector of sorts that could be faulty/intermittent?
Have used 3 cans of injector cleaner - no change.  Thanks for any
advice.