Help with Misfire

[bissbb]

2004 Expedition 4.6, 107k. misfired near the top of a fairly steep 2 mile hill. Serv Eng light on immediately. Sounds louder than normal along with rough running and very sluggish performance. Code P0303 #3 cylinder misfire. Pulled COP and plug. The ground electrode on the plug is nearly gone. Put in new plug and COP but no improvement.

 

[bissbb]

Next Step? - based on other posts I'm thinking the #3 injector needs replaced. Then the dreaded cat conv job! Any feedback greatly appreciated

 

[Bowesmobile]

The next step is check wiring to that plug. Look for breaks or a shorted wire. Also, I would swap a coil from a one you know works for the one on cyl. 3 and see if the misfire follows the coil. New parts have been known to be bad from the factory.