OK... 1999 Pontiac Grand Prix GTP 3.8L Supercharged Service Engine Soon has been steady on and now it blinks so I stopped by AutoZone for a free scan...4 codes came up in this order...P0303- cylinder#3 misfire, P0203- fuel injector #3 circuit condition, P0420- catalyst efficiency low bank 1, and P0741 TCC stuck off. I think all these codes are triggered by the #3 cylinder misfire. In regards to the P0203 code any misfire will cause the PCM to shut down the injector control circuit for that specific cylinder. In order to fix the cyl #3 misfire I changed all spark plugs( properly gapped at .060) and wires. The car sputters when accelerating and the boost kicks in earlier then it should and the motor shakes in drive and at idle. Also my fuel economy has gone down a few MPG. I had exhaust work done in the shop about a week ago after I rode over a rock and it caused a hole in the exhaust pipe between the cat and exhaust manifold. The car was running great for a few days after I checked some spark plugs but the SES was on but not blinking. Ever since the SES light flashes, the car runs terrible. The spark plugs and wires are NOT the problem. Can anyone provide me with some assistance on how to correct this misfire in cylinder #3? Thanks for anything.
