P0300 Still there, after cap rotor

I agree the plug looks okay. Since the problem started 6 months ago after replacing the wires, cap, rotor, and plugs I would suspect the wires, cap, rotor or plugs are the cause. The least expensive approach is to verify the plug wires are connected in the correct order. Do you still have the old wires if so I'd replace the new wires with the old and see what happens. Make sure you have the correct rotor and the correct cap and the cap and rotor are seated correctly.

bsamole said:

I agree the plug looks okay. Since the problem started 6 months ago after replacing the wires, cap, rotor, and plugs I would suspect the wires, cap, rotor or plugs are the cause. The least expensive approach is to verify the plug wires are connected in the correct order. Do you still have the old wires if so I'd replace the new wires with the old and see what happens. Make sure you have the correct rotor and the correct cap and the cap and rotor are seated correctly.

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Hey, thanks for the advice! I discovered a while ago that I had a burned spark plug wire that fell out of the mount and was rubbing against the exhaust manifold and arcing to the block. Since then, no misfires have been present, and p0300 has not come back. for now, at least...I am now chasing an oil pressure sending unit.

I was going to ask about the fuel since you stated 200 miles in 6 months...maybe bad gas.

Seems you may have sorted it out though.

dkad260 said:

I was going to ask about the fuel since you stated 200 miles in 6 months...maybe bad gas.

Seems you may have sorted it out though.

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Yup, I got it. Thank you!

OR VietVet said:

This post is in the wrong section, for one. The plug looks fine, IMO. If enough oil leaks from a valve cover and damages the wire, then you can have a miss but oil around the base of the plug, where it threads in, will not cause a misfire, that I have ever seen. AC Delco cap and rotor, correct? I seem to remember from the other thread that they are. Did you do a wet and dry compression test?

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What is a wet and dry compression test? Please explain if possible.

Remove all plugs, do a DRY compression test on all 8 cylinders, with a battery charger attached and charging. If you have any weak cylinders, squirt a small amount of oil in the spark plug hole and do the compression test again on that cylinder. That is a WET test. If compression increases, that means the oil sealed at the piston rings and brought the compression up and you have rings problem on that cylinder. If compression stays the same, the compression problem on that cylinder is located in the valve train.