Mechanics

MULTIPORT MISFIRE

1999 Pontiac Sunfire

I have a 1999 sunifre has a 2.2 4 cly engine, 97,000 miles, the check engine comes on and the car loses power like it is struggling to run, and then it will pick back up power and run good and then lose power again and the check engine light will flash. Things that have been replaced on it are the water pump, radiator and thermostat, new spark plugs and spark plug wires, also replaced the coil packs. Also replaced the 2 oxygen sensors. When using the code reader to get the error code for what is wrong it give a code of P0300, what would cause the care to multiport misfire? This model doesnt have a rotor cap it has coil packs. I forgot to mention that sometimes the car will run without any problems at all and then it will be like it is gonna quit running and then next time it will run witout any problems at all.
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Angel45304
December 21, 2006.



I don't know where to begin since there can be many different causes for misfires. Suspecting the spark plugs, wires and coil is a good start. Since you don't have any other error codes this can narrow it down a bit. Does your car have a rotor and cap.
This is also a good possible reason. Dirty injectors or low fuel pressure can also cause misfires. A vacuum leak can also cause misfires. And finally low compression due to leaking head gasket, burned valves, worn valve springs, or worn cam lobes. Good luck hope this helps. Backyardmechanic : )

Tiny
Backyardmechanic
Dec 21, 2006.
I had this same problem on my 2000 Grand Am 2.4L
It turned out I had a bad coil pack cover when the engine got hot it would arch through the coil pack cover and number 2 & 3 cylinder would not fire. I am not sure if the 2.2L has the same setup. If it does look at the coil pack cover and if it looks black through the bottom of the cover where the coil pack leads run to the spark plug boot ends I would replace the coil pack cover. Good Luck

Tiny
Fryertuck
Jan 24, 2007.
I just spent several hours and replaced both coil packs and coil houseing along with plugs and plug boots did not solve the problem I got lucky while looking at the fuel rail I discovered that the fuel regulator was leaking fuel right into the
throttle body replaced it and it runs great and no misfire

Tiny
Royfleming
Nov 16, 2012.