Idle problem (IAC motor?)

Get yourself a vacuum guage and check for vacuum leaks.

ok Steve ,thanks

Probable vac leak somewhere.

Usually when you buy a vacuum guage it comes with instructions or a chart that will tell you what the different readings mean. Mine has it written on the face of the guage. Also I think the Haynes manuals detail how to use a vacuum guage, and I'm sure there are plenty of "how to" articles on the 'net.

If you find there is a leak somewhere, check all your vacuum hoses for cracks, loose connections, breaks, kinked, collapses, etc. Check the intake pipe and air filter box for holes/blockage/loose joints/etc. If all checks out, maybe it's a gasket somewhere. Take a can of throttle body cleaner, other people probably use other things, and spray it around the mating surfaces of the intake manifolds. If there is an intake vacuum leak the cleaner will be sucked into the hole and the engine speed will change. I think I've heard people use propane as well.

Your timing could also be out, but a vacuum guage should be helpful in determining if it's a vacuum leak or a timing issue.

Steve

My father taught me to use WD-40, which works very well but makes a mess. The advantage of using propane (and it only takes a little) is that it leaves no residue. The disadvantage is that you can't see it. I switched to using an unlit propane torch a decade or so ago and my engines look much nicer than my father's.

--scott

You might want to inspect the throttle bore and plates for carbon build up. You can clean them with spray throttle body cleaner and an old toothbrush if necessary.