My grand prix will start about once every month. It will run perfect for about 2 or 3 minutes and then it will start chugging and eventually quit. I have replaced the fuel pump, plug wires, crank sensor, coil packs, checked the camshaft sensor and it was good. I cleaned the maf sensor and confirmed that it has proper fuel pressure. There are no codes when i scan the ecm but the history shows that misfires on all cylunders but two. Number 3 cylinder has over 200 misfires. Also I cut the exhaust in front of cat converter and when I would try to start it the car sounded as if it were out of time because I could hear it backfire with the exhaust uncapped...please help!!!!
Well from what it sounds like is that it is your fuel injectors try going to a full service garage and have them clean the fuel injectors if you cant get it there go to auto zone and pick up a can of sea foam and do it your self thru a vacum line such as the brake booster there is a vacum line that comes out of that and goes straight to your cylinder that will help you there its recomended once a year or every 15000 miles good luck hope it works for you
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