P0304 Misfire

newman4242 · March 16, 2009

Looking for some help......I have a 98 silverado 305 vortec with 160,000. It has a trouble code of p0304. Misfire in cylinder 4. I changed the plugs, wires, cap, and rotor. Cleared the light. started it up and the rough idle was still there. Took a test drive and the light returned with same code. Did some searching and see that the cat could be bad. Now i have had the rotten egg smell occasionally, do you think that I should get the cat replaced for that side. The cap and rotor did not look the best, needed to be changed. Any other ideas? Thanks

Draenor · March 16, 2009

I would try a compression test first. Also are you getting fuel to that cylinder? Could be a bad injector. You could swap it with another to see if the code follows. If those look good then it could be the cat, funny your not getting a cat code.

newman4242 · March 16, 2009

I would try a compression test first. Also are you getting fuel to that cylinder? Could be a bad injector. You could swap it with another to see if the code follows. If those look good then it could be the cat, funny your not getting a cat code.

I think I will...it seems to run alright at a higher rpm. Trying not to take the intake apart if not needed.