I have an 89 Grand Prix with a 3.1L V6. I just replaced the alternator after the car had been sitting for about 2 months. Now when starting the car I have to gun the gas for about 10 secs. so that the car will actually start up. Once running it runs fine for about 4 or 5 minutes and then the RPMs start fluxuating from 1,000 to 200 and the voltage meter also fluxuates in tandem. It acts like it is going to die and then the RPMs will surge back up. I have added some new gas and some fuel injector cleaner. Could this problem be caused because of the old gas sitting for two months? Any help would be greatly appreciated.

Hmmmm I doubt that the gas would cause a problem like that after 2 months.... I'll put this up top for you. Hopefully someone else can help

Check the FPR?

I dont know if this will help but i used to have a pontiac grand am w/ the 3100. Mine did the same thing. This is also one of the symptoms i have seen, you dont have your headlights on but the highbeam light is on in the cluster. Dont know if yours is doing it but the ypical issue for this is the voltage regulator. if i remember right the regulator is located behind the cluster on the pontiacs. i can check into that further and let you know but i believe that is your issue. I dont want to worry you but the car has a really bad tendency so you might want to check it out. the 3100 is horrible for blowing intake manifold gaskets. when this happens your coolant and oil mix and before you know it you have mud in your engine. I have replaced 100's of them so if you need help or advice let me know and it' wont be a prob. Good luck and i hope this was helpful. :rockon:

My hi-beam light is not on but my service engine light is lit-up; not sure if it is connected with this problem or not. I will check on the voltage regulator, as a friend of mine suggested it too. Thanks for the help.

My hi-beam light is not on but my service engine light is lit-up; not sure if it is connected with this problem or not. I will check on the voltage regulator, as a friend of mine suggested it too. Thanks for the help.

I would suggest going to auto zone or some place like that and have them pull the error code. Your alternator may have gone bad again. In my Subaru I went through 3 alternators in one months time so it is possible. You can have the input on the alternator tested and see how its output is and maybe rule that out. I hope that may help.

My hi-beam light is not on but my service engine light is lit-up; not sure if it is connected with this problem or not. I will check on the voltage regulator, as a friend of mine suggested it too. Thanks for the help.

Anytime. hope you get it fixed. let us know how it works out. Best of luck!!