I have a 2007 f-150 5.4 I constantly and receiving a misfire code on #3 I have changed the coil x2 I have changed he plug x2 I have swapped out coil to see if misfire changed and it did not . There is a slight stumble and misfire and when I really get on the gas it misfires even more and rattles the engine. I have been to 2 tranny shops and they Both agree its the engine Can it be Catalaytic converter ? Bad connector wire ?
I have compression tested cylinder and its good, checked intake for cracks all good

I need Help !
Rob

 

It could be a wiring issue (meaning grounding or abraded wires), or something with the ECU.

 

Turn the ignition on and check the voltage at the cop.
Swap injectors around to see if the misfire moves.
Here is a video you might want to watch.

 

Why would you be going to a transmission shop for an engine concern???

Lots of things it *might* be.

Might be a bad/fouled injector. Could easily be a mechanical concern with the base engine. Burned valve, cracked head, head gasket, etc are all on the table. A dry AND wet compression test would be valuable. A coolant check for exhaust byproducts could be useful.

 

I went to the transmission shop at first thinking it was overdrive issue I had been reading that it could possibly be clip that
Servo Clip was broke etc

 

I have had compression tests, head gasket has been looked Coolant check has been done, injector test and switch is next i guess or pull that valve cover as stated in video

 

Next time CLEARLY STATE everything that has been done. That way, you won't waste our time...

 

Well if you CLEARLY would have read original post I did state what was done that was relevant at the time YOUR time is wasted with answers like that !