I have a 2000 f250 with a v10 in it. It started running rough so I decided to change the spark plugs. Got all 10 changed and the problem was still there. Sometimes it will run fine but others it misses really bad and the tone of the truck changes. I am not mechanically inclined but I try to resolve some of the issues myself. Checked the codes yesterday and it was giving me a po304 and po308 codes which I believe is the code for a misfire in cylinders 4&8. Changes coils and boots today and nothing changed. Any thoughts??

 

So you have already changed all the spark plugs . After that you got P0304 and P0308 error codes ( it was running rough all along) . You had changed #4 and #8 coils and boots and no improvement about p0304(8) codes .

Did you double check all electrical plugs (both coil plugs and injector plugs ) ?

well, may be #4 and #8 injectors ?

Run a "reputable" injector cleaner first and clear the existing error codes by removing battery cable , see if it improves .

Good luck,

 

An easy test or way to better isolate your problems would be to individually disconnect/unplug the COP and injector connections, those from the wiring harness, one at a time. If the miss remains the same after removing one of the connectors its probably likely the COP or injector is at fault for that cylinder.

Reusing older boots and accidental breaking the locking tabs of the COP and injector connectors is also known to cause these same problems. I'd look to these areas first as it may be that simple.

FWIW the replacement connectors if needed are available through NAPA or most any other good full line auto parts retailer. COP connector p/n is EC259 from NAPA.

HTH