I have a 2004 SD with 5.4 that is running pretty rough both at idle and driving. Truck shakes a lot at lower rpms. I have a scan tool and had a misfire on cylinder 4 so I replaced the coil and the plug. Also replaced the idle air control valve. Plan on replacing O2 B1 S2. (One of my codes) even after replacing the coil and plug I'm still getting misfire detected from cylinder 4??? Other codes I had were misfire detected on he first 1000 revolutions. That hasn't come back though.

 

If its only cylinder #4 I would possibly suspect the injector. If the code resets quickly after clearing it then perhaps swap injectors and see if the misfire follows. They are about $120 i think to replace each.

 

Thank you! I'll have to check that out when I get home.