Tips to Troublesoot Cylinder Misfire?
 

I recently finished a head gasket job, and now I have a code p0304, cylinder #4 misfire.

If I pull out the plug and leave it connected to the plug wire while the engine cranks, I can see it spark. The plug comes out of the head wet and smelling like fuel. And the cylinder has 155 psi compression. Is there something else I should be checking?

I suppose it's possible I could have crossed plug wires on the coils, but I've done this about four times before, so I feel fairlyconfident I got it right. Plus, wouldn't that cause at least one more cylinder to misfire?

Suggestions?

If you crossed a wire, you would have 2 mis-fire codes. Did you install new 8mm silicone wires and new plugs?

Make sure you have a good connection on the coil. If it is an old wire it could be broken in spots and when you bend it to check the spark you see it ignite causing you to believe you have spark. I would test with another wire. Swap the wires to the next cylinder and see if the misfire follows. If it does you most likely have a bad wire. If it doesn't move you might check to make sure the fuel injector is functioning.

The wires are magnecor 8 mm, less than 6 months old. So I think they're good. The plugs are bosch +4, about 2.5 years old. They were pretty dirty when they came out of another engine. However, I swapped cylinder 4 plug with another and there was no change.

Re: the injector, since the plug comes out wet, I know it's doing something.

I'm perplexed.

Did you swap the wire?

No. Haven't done that yet b/c that's more work! Guess that's my next step though. So even though wire will arc strongly if pulled from the plug with the engine running, you still think it could be bad? And again, these are basically new wires.

If I have to pull the upper intake, I'll probably swap the injector too for good measure.

2 Ideas, 1, you have a cracked plug, or when removing the wires, you pulled the boot and tore the wire loose inside the connector.

X2

That's kinda what I was meaning when I said "it could be broken in spots and when you bend it to check the spark you see it ignite causing you to believe you have spark."

Magnacor has been known to fail...like any other part, nothing is ever 100%.

Also the gas could be from a leaky fuel injector.

Try just swapping the plug ends with another cylinder and see if the misfire continues. Also are you clearing your codes before testing each time?