I have a P0300 random misfire that is robbing power and wasting lots of gas.


Asked by Dec 31, 2013 at 07:32 PM about the 2003 Pontiac Sunfire

Question type: Maintenance & Repair

When I am idling my engine light stays on solid.  As I drive the RPM's go up and up until i let off the gas but the light stays solid.  As soon as the transmision shifts to the next gear, the light flashes and stays flashing until i come to a stop and then it is solid again.  Any ideas what is causing the problem?  i originally thought it was a bad coil but when i replaced it it wouldn't even start up the car. I put a diffrent brand new coil on it but the same result.  I put my old one back on and it starts up but runs and idles rough with no power at all.

6 Answers


http://www.obd-codes.com/p0300 -- this may help

6 out of 6 people think this is helpful.

Sounds like you're misfiring under load. If you have 100,000 miles or more on your Sunfire you're due for a tune up (iridium spark plugs and new spark plug wires). A flashing check engine or service engine soon light is warning you that the catalytic converter is being damaged. Try the tune up first, if you're due. HTH. -Jim

2 out of 2 people think this is helpful.
Best Answer

I had bosch platinums put in about a month before the problem started. I pulled them and when I tried to replace the coil with a new one i put AC delco plugs in. the coil would not even start my car up but the old one does. I put a second new coil in with the same result so i don't think I got a bad coil from parts store.

3 out of 3 people think this is helpful.

I have a 2.2L OHc Ecotec. It has no wires just a coil on top with boots that slide onto plugs as you tighten the coil cover up.

4 out of 4 people think this is helpful.

I see. Well, each spark plug has it's own coil. When you replaced the spark plugs did you replace the ignition coil boots as well? They should be replaced at each tune up. Also, try this. Wait until it's dark outside. Open the hood and start the engine. Look at and near the spark plug area and all around the coils. Rev the engine several times. You're looking for sparking. Any time you see a spark, that's a misfire. Pay attention to what's sparking. A coil or boot, a plug for a coil, etc. That's what will need to be replaced. You can see this much easier after dark. If there's no sparking, get a spray bottle and mist the area near the spark plugs and coils with water. Then repeat the test. HTH. -Jim


Check out this video I made might help! https://www.youtube.com/watch?v=dtNQWj26RNU

3 out of 3 people think this is helpful.

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