Mechanics

P0300 CONFUSTION

1998 Pontiac Sunfire • 4 cylinder FWD Manual • 110,000 miles

I have a 03 pontiac sunfire, pulled an p0300 code (random misfire) and a bad cat code. I replaced the upstream O2 sensor and the cat code went away. I've replaced the plugs, did an oil change, compression reads around 170 on all cylinders, injectors work fine (noid light test and visual inspection of sprays), replaced coil pack, and wiped down the throttle body. It runs really rough, major power loss, and the cat is heating up to extreme temperature (I believe due to the excess fuel being sent to it). What do I need to test or replace next?
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Dumenuf2talk2u
February 15, 2011.




What color are the plugs? Did you do an individual coil/cyl spark test?

Tiny
Fixitmr
Feb 15, 2011.
The plug color? It was black, almost fouled but only on cylinder 1 and 4.

I'm not sure how to do a ind. Spark test on it as its one single coil pack

Tiny
Dumenuf2talk2u
Feb 16, 2011.
I'm not sure what you mean by the plug color? The #1 and 4 were foulded out if that was what you were asking.

I'm not sure how to do an ind. Spark test as its a single coil pack and there is only a spring that moves the current from the coil pack to the plug, held in place by pressure when you screw the coil pack down
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Tiny
Dumenuf2talk2u
Feb 16, 2011.
So you have/had 1&4 which has their own coil fouling out. Have you checked plugs since you changed them? Did you change ignition module? Do you have good spark on 1&4 now?

Tiny
Fixitmr
Feb 16, 2011.
1&4 don't have their own coil pack, its one long strip that connects to all four cylinders. I did recheck the plugs and 1&4 had a heavy carbon build up. I cleaned them off and reinstalled. I did not change the ignition module as I assumed that if it went bad it would deliver no spark at all. I don't actually know that i'm getting good spark in any cylinder because I don't know if I can or how to do an ind spark test on a coil pack of that type

Tiny
Dumenuf2talk2u
Feb 16, 2011.

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