Hello!

The symptoms you describe are consistent with an engine vacuum leak. On this model, the usual place for a vacuum leak is at the gasket where the upper intake manifold (plenum) joins the lower half of the intake manifold. When the gasket gets old and brittle, it tends to suck inward creating an air leak. Use a can of spray carb cleaner or an unlit propane torch passed around the gasket area to see if it affects engine speed, indiacting an air leak.

Another possible source of a vacuum leak would be an EGR valve that is stuck partially open with carbon deposits and not closing completely at idle.

If it is not an air leak, you may have a failed idle air control valve. This valve bleeds air around the throttle plate in response to computer commands; this is how the computer controls idle speed. If the valve does not respond, it can cause the car to stall at idle.

I hope this is helpful; if so, an accept would be most appreciated! thanks!