obeonec

I have a 2006 5.4L F150.

I am encountering a misfire on the #3 plug.

The only OBD error messages I receive are from misfire on #3, no other faults.

I have checked the plug, and it looks pretty good.

I have recently changed all COPs.

I have removed the injector rail and checked and cleaned all injectors.

I have removed the wire connector from COPs and checked the voltage while the vehicle is running.

The #3 connector is measuring around 13.6V

The other COP connectors I measure 0.17V to 0.4V.

It appears this low volt reading is due to the neg signal wire closing and opening.

I brought it in to a mechanic and he indicated the computer needs to be replaced, no signal was getting to COP.

So this appears where I am at.

I have hence gotten a LED test light and verified the other COP connector wires cause the test light to flash, while the #3 COP wire connection to just stay on all the time, no blink signal.

Any ideas as to what the problem is?

The engine sounds pretty good, maybe a slight tick sound. But the misfire wobble is apparent.

I figure I will change the computer at this point, since it appears this is where the issue is.

What else could interfere with the COP neg signal? It is pretty clean in the engine compartment, and no visible problems with the wires fraying on the accumulator, as I have read reports happening.

Is it the cam that makes this negative signal wire open and close?