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misfire code PO305

05-21-2004, 03:47 PM
Obout every other month my check engine light will come on and the engine will run rough. After 5 minutes or so the engine will be fine and the light will go off. I checked the obd computer for codes and two months ago the code read PO300 random misfire. Two days ago the vehicle did it again and I got a PO305 cylinder 5 misfire code.

My question is do you think it's the plug wires or an injector problem? I checked the wires 3 months ago and they were fine, however they are still the original wires. I have a 1997 bonneville with 93,000 miles. I don't have the equipment to re-check the wires again as I borrowed it the first time from someone. My bonneville is running fine again, but I'm sure the misfire will happen again. I've changed my spark plugs also, but still the problem comes up.

05-22-2004, 12:27 PM
Without a doubt I would install new wires & new coils as a preventive maintenance.

supercharged gt
05-23-2004, 09:49 PM
do the wires deff. go from there they can cause big headaces if there misfiring

05-23-2004, 10:00 PM
Another way to check wires is to start the car and spray a mist of H2O on the wires. See if a little light show occurs. In any event, it's time for new wires I'd change them.

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