I'm stumped! Our '96 chevy 1500WT w/4.3L V-6 (5-speed manual/air/2WD). With 170K miles seems to have a mind of its own. It doesn't have cruise control, BUT. Often (NOT ALWAYS, though!) You take your foot off the gas and the truck keeps going along at the same speed! Disengage the clutch, and the engine RPM stays at 1500-2000RPM until (and here's the catch.) We come to a COMPLETE STOP! The engine then drops right down to a stable idle of about 800 RPM as soon as the wheels stop turning!
I have removed, but not replaced the IAC valve. It looks like new and does not stick at all. This happens in any weather, engine cold or hot, and there are no engine codes set. This has been going on for 4 years and 50K miles with no change. Any ideas?
Thanks in advance.