when was the last time u had a tune up?
dirty Fuel filter
Spark plugs and wires #1 u should change them.
Distributer caps and rotors or
it could be ur fuel pump is weak.
also what is responsible for ur idling is ur air idle control valve which is located on the intake where the air enters the intake manifold this could easily need adjusting. try this one first. if not then ur spark plugs.
First all cars idle at around 800 to 950 so 1500 signals a problem.....If the air idle control valve is sticking for gunk and buildup it will idle bad up or down. I'm assuming its a 3.8 v6 car same go for the 4.6 v8 car it should be cheap to get the AIC valve replaced.
take the idle air control sensor off and clean it and clean out the throttle body with throttle body cleaner. it would,nt hurt to check the air filter either. it could be clogged up and choking it out.