dthsmarsh
Member
Hello ... I have a 2005 Expedition limited, 5.4L. I'm having a constant #3 misfire issue, CEL code P0303. Usually happens while going uphill and the power drops way off. Sometimes will clear itself after getting up the hill but will eventually come back. Gas mileage drops way down too.
I've changed out all 8 COP's and all 8 spark plugs within the last 2 months. I've swapped the #3 cylinder COP with another cyl and the problem always stays on the #3 cyl. Swapped #3 spark plug and the #3 fuel injector with another cylinder too hoping to see the problem would move to the different cylinder, but always stays P0303.
I've ohm'ed out the wiring between the PCM computer and the COP and fuel injector and all seems fine (shook the heck out of the wiring bundles to see if there's an intermittant wiring problem but all seemed good).
I've run Seafoam through the engine to see if there's a sticky valve or something. I haven't tested compression yet in that cylinder but that may be next.
Any idea anyone? I can't think of anything left besides COP, plug, and fuel injector that is specific to the #3 cylinder. Maybe a bad PCM?
Thanks for any help!!
I've changed out all 8 COP's and all 8 spark plugs within the last 2 months. I've swapped the #3 cylinder COP with another cyl and the problem always stays on the #3 cyl. Swapped #3 spark plug and the #3 fuel injector with another cylinder too hoping to see the problem would move to the different cylinder, but always stays P0303.
I've ohm'ed out the wiring between the PCM computer and the COP and fuel injector and all seems fine (shook the heck out of the wiring bundles to see if there's an intermittant wiring problem but all seemed good).
I've run Seafoam through the engine to see if there's a sticky valve or something. I haven't tested compression yet in that cylinder but that may be next.
Any idea anyone? I can't think of anything left besides COP, plug, and fuel injector that is specific to the #3 cylinder. Maybe a bad PCM?
Thanks for any help!!