New problem... very annoying!
 

Hey folks, so now that I replaced my alternator, cleaned all my fuel lines, flushed the cooling system, and did a tune up... my 1990 4cyl trooper still has an annoying problem!

When I start it, the engine runs at around 800 rpm - pretty normal. However, after driving for a bit, at stopping, the engine revs (REALLY BADLY!!) if the heater is on. Think... going from 800 to 3000 rpm at a stop!!) It calms down a little if it is in gear, but in neutral, it is quite the nuisance! Before I did a hot-machine coolant flush/cleaning, i attributed this to the fact that my entire cooling system looked like the arteries of a fat man... but the problem has persisted.

Any ideas of the culprit?

Thanks!

Thank you very little for looking, but not replying! I've been tinkering and have yet to find the problem...