Pontiac Repair: 1996 pontiac grand prix 3.4L, manifold gaskets, pontiac grand prix

Question
I have a 96 grand prix with a 3.4L eng. when i start the car it will idle rough and go from 700 rpm to 2000 or higher then back down.  But runs great down the road

Answer
Hi Jeff:

The engine more the likley have a vacuum leak. The lower intanke manifold gaskets leak on these engines when the engein is cold and as the engine warms upo the gaskets seal back up and it will run smoother and the idle will settle down. Good luck :)