2003 Pontiac Grand Prix - CEL and O2

So I bought this car about 2 years ago, the check engine light came on about a week after I bought it. Still ran fine but brought it in to run the codes. Both upper and lower o2 sensors. I replaced the top and left the bottom. Been running fine until about a week ago, then noticed the engine was not heating up. It is winter an cold now. Decided to change the thermostat. Fixed the heating problem and ran fine all morning. Then got in it to run to the store and now the check engine light turned off and the car is running like crap. Spitting and sputtering upon slow acceleration unless I hammer on the gas, than it usually goes fine with little to no sputtering. I don’t know y why the light went off and now running like this.

PS, it is a gtp with the supercharger. Also I had the resonator rust out and fall out of the exhaust about a year ago. I replaced it with just a straight pipe and it was running fine. Then about a week ago when the heat issues started I had the straight pipe fall out and haven’t had a chance to fix that yet, but it was running fine just really loud without it.

You may have to stop fixing this car. If you fix one thing, something else will go wrong. I had a car like that a few times. Your question helped me remember an NFL guard for the Giants. Bill Parcells said that Brad Benson is like an old car. You turn the key and the wheels fall off. I was trying to remember his name after I thought of the Parcells quote. It’s the main reason I replied.

I had an O2 sensor that went rogue and caused almost the same problem last summer. It was on a Dodge Caravan. Hopefully your car can be fixed because I would want it fixed if it was mine, this time.

Turned off or burned out?

Turned off, the next day it came back on again

… and after his NFL career, Benson opened a Mitsubishi/Hyundai franchise in Central NJ, which quickly gained a reputation for being even worse than most dealerships. After his son got his face in serious legal trouble (drunken driving, atrocious assault with a motor vehicle, plus fleeing from the crime scene), and Brad tried to buy his son’s freedom, the business went downhill to such an extent that he wound up selling it.

FIXED, I had brought the car to the local auto parts place to hook up to there scanner and they said all it gave them was the o2 sensor code. It didnt seem like they even hooked it up right or waited for a scan. So a couple days later I decided to bring it to an auto parts store in the next town over and have them hook it up to there scanner and sure enough it threw a code for a cylinder 3 misfire. Swapped out plugs and wires and now it runs how it should.