miketo

96-grand am 3100-v6/auto. 147000. after sitting for about 10 min. and restarting, the engine stumbles or won't respond to the throttle, after afew hundred feet it clears up and is fine. vapour lock? this has happened twice while engine has ideled for a few min.
gas tank and filter have been changed.

GTP Dad

How many miles? It sounds more like you have a problem with the injectors leaking down when the car is off causing the engine to load up when you restart the car. Also you may want to check the fuel pressure regulator to make sure it is maintaining proper pressure on the fuel rail when the car is off. A bad regulator will give similar symptoms.

GTP Dad

The fuel pressure regulator is located on the fuel rail on top of the engine. It should have a vacuum line going to it. You may have to remove the phlenum in order to get to it but I doubt it. It will have a round vacuum pot on the top and both fuel rails should connect to it. You may also want to look at the ignition module. Sometimes when they start to go bad it will cause a similar problem. It is located directly under the coil pack. Good Luck!

Hoags

I have to concur with GTP Dad. I recently went through this with my 96 2.4L, however my contition was much worse than what you are describing with your 3.1L. But prior to my poor running condition I was having a condition similar to your's. I have a manual tranny and for the past two years I have had a stumbling problem when shifting fron 3rd to 4th and 4th to 5th. After chabging the ign. module and having the injectors professionally cleaned [ not the fuel additive in the gas tank]. My Grand Am GT is now running better than ever, no more hesitation, and re-gained all the power that the car has lacked for a very long time. I picked up a used module from a guy that worked at the repair garage and the injector cleaning ran about $60.00.

I hope my experience will help your situation, good luck,
Dan

miketo

thanks to GTP DAD and Dan. I'll put your knowledge and experience to work and let you know how it turns out. CHEERS