2003 Pontiac Grand Prix fuel system problems.

CHRISTALREYNA

MEMBER
2003 PONTIAC GRAND PRIX
6 CYL
4WD
AUTOMATIC
99,700 MILES

I have a 2003 grand prix gtp 3.8l supercharged v6 automatic. After I fill up with gas I go to start it will turn over but not crank. I try it again but have to give gas and then set there with foot on pedal cause if not it would die. Even when I take off and slow it acts as if its gonna die. And it only does this that one time after filling up, all other times it starts right up no problem. And I only use premium gas. Also theres a few times ive been sitting at red light and it will die out of nowhere but starts right up. Also at times when idling it surges up and down a few times then stops. One other thing is when idling if you remove gas cap it starts surgeing til the cap is replaced. It has brand new fuel pump, charcoal canister from dealer. And replaced with new gas cap. So pretty much everything new around gas tank. Im thinking its under the hood somewhere. And gas lines been cleaned out.

1 Reply

JASONRAY

MECHANIC
213 POSTS

Woo. That's a tricky one. Part of it sounds like there is a vacuum leak under the hood but other symptoms contradict that. Removing the gas cap would, theoretically, only affect the evap emission system. The system pulls a very small vacuum on the tank to recycle gas fumes through the engine. Perhaps removing the gas cap causes a vacuum leak. Ah, ha. I bet the purge solenoid is stuck open, allowing the engine to constantly pull a vacuum on the tank, instead of when the PCM tells it to. When you remove the gas cap, it's just like unplugging a vacuum line from the engine. You'll need to find the single vacuum line that goes from the intake manifold to the purged solenoid and plug it. Then start the engine, and remove the gas cap and see if it still acts up. Let me know what you find. That's interesting.