Being the check engine light is on, that means that a problem has been detected by the vehicle's ECM and has produced a trouble code(s) and there is no way of knowing until those trouble codes are extracted from the ECM, you will need to take your vehicle to a reputable mechanic that has the proper equipment that can extract the trouble codes in order to perform the proper diagnosis and repair.
Because you have a problem with your engine. Don't expect to get it diagnosed on yahoo....go get an obd2 scan at an auto parts retailer and take the code to your mechanic so he or she can verify the issue.
It's running "ruff"? REALLY? Christ, is our educational system THAT bad?
Anyway, without a code no one here can help you, it could be on for hundreds of reasons.....
Get it checked and fixed asap. Doesn't sound good and needs to be taken care of before it gets worse.
2003 Pontiac grand am
