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Misfire on cylinder 3 and 4

B

bhuyser

New member
Anybody have trouble with a 2004 supercharged grand prix with a misfire in cylinder 3 and 4. Especially under heavy load with pedal 3/4 to all the way down.

Check engine light is blinking. Both spark plugs showing misfire.

The catalytic converter does need to be replaced.

Compression is good.

You can tell a little rough miss during idle but no codes during idle.

Anybody have this trouble before?
 
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Have you replaced the plugs and wires? Or the coils? Or the ICM?

Just because your converter is good doesn't mean squat...get a tune-up if you haven't done one...oil/oil filter/PCV valve, etc.

Clear the code from the PCM.

Then enjoy your car not hating you.

Also, welcome to the site...
 
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Replace your cat before you hurt the motor.

The likely reason behind 3 and 4 misfiring is they are the two middle cylinders in the front and rear. Therefore naturally they tend to run hotter than the other 4 cylinders.

Now add back pressure of a bad catalytic and you heat them up even more leading to misfires, probably knock and potentially damage.
 
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