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Cylinder #3 Misfire - SES Light Flashing

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pc305577

New member
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.
 


My car has a split personality... the last few days the SES light has been on steady yet the car runs like when I first got it with power. There is this rattling noise that comes from the passenger side under the hood either way if the SES light is flashing or not. When its not flashing and running good the rattling goes away as soon as I press the accelerator anytime and there is no shaking. It seems it does not affect the way the car drives. When the service engine light is flashing the rattling gets louder when I hit the gas. Lately (most of the time) when the SES light is flashing the car runs terrible (hesitating, sputtering, shaking when idle and in drive).
 
there is an ez way to check the coil packs. just use a multi meter set it to read omh i don't remember of hand what they should read but they should all be around the same number.
 
pc305577 said:
My car has a split personality... the last few days the SES light has been on steady yet the car runs like when I first got it with power. There is this rattling noise that comes from the passenger side under the hood either way if the SES light is flashing or not. When its not flashing and running good the rattling goes away as soon as I press the accelerator anytime and there is no shaking. It seems it does not affect the way the car drives. When the service engine light is flashing the rattling gets louder when I hit the gas. Lately (most of the time) when the SES light is flashing the car runs terrible (hesitating, sputtering, shaking when idle and in drive).
Click to expand...
about the the noise under the hood. hold your ear up to the snout of the s/c. if thats where the noise is coming from all it is, is a polyurethane cupling. it connects the pully sharft to the screw. its only $100 to do it your self
 


i would think the number 3 injector is at fault.i have never known an injector to be shut off with a missfire. my injector kept pumping fine when the piston was shoved and pinned sideways in number 4.
 
When the SES light is flashing it means that the fault is occuring at that moment. When the light is on it means a fault had occured and now it is stored in memory and waiting for you to do something about it.

Is it flashing during WOT?

Did you clear your codes after changing your plugs and wires. Did you get code reread to see what they say now?
 
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