Idling high when stopped or in park

I would suspect a possible vacuum leak. If it is actually stalling, it sounds like it can be a large leak. Check the large intake hose between the air filter box & the throttle body. check that it is properly clamped at both ends, and that there are no leaks along the hose itself. also, check the PCV hose, it is a short hose leading from the intake plenum to the pcv valve (next to the firewall near the middle/passenger side of the engine compartment). anoher hose to check is the hose from the brake booster to the intake plenum (also along the firewall).