Code PO304

[rego]

I have a chance to buy a 2000 XLT with the ohv 4L. It's throwing PO304, missfire cyl 4. What would the possible culprits be? I'm worried about head cracked or head gasket. Odometer shows 96,000. Thanks.

 

[jremington59]

It could be any of the following.

Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer

 

[greasemanicure]

Amen to the above. Changed plugs first. Then wires. Then on to more troublesome stuff. Then back to new plug 4 which was dead short. Happy hunting