My sevice engin light came on and it gave the PO 304 code. Miss fire on 3 4 cylinder. should I replace the cop for that cylinder or is there a boot to replace. it is on a 2001 f150 2wd surecrew cab with a 5.4 in it. Just thought I would see what you fine people on this site have to say. I don't want to take it to the ford stealership if I don't have to. Thanks Tim

 

P0304 is a misfire on the number 4 cylinder, rear most passengers side. If it was me I'd replace the spark plug and C.O.P. both at the same time so I wouldn't have to do it over again. While your there make sure the coolant hose above it isn't leaking, the clamps loosen up. Good Luck

 

how many miles? you should do all the plugs at about 100K. If the plugs are not original, you might need just the COP. change out #4 with #1, clear codes and see if it comes back. IF you get 301 next time, buy a new COP.

 

Simplest way to check for the source of the problem.

 

It has 120000 on it. The plugs were changed at 105000.I cleared the code out and have drove it a few miles and it has not come back on.

 

could be moisture on the COP. if it does it again, pull the #4 COP and see if the rubber boot is swelled from oil or antifreeze contamination. that causes a miss fire.