hello everyone,first time poster so please be easy if this has been covered before
My wife's 2000 F-150,5.4L set a code P0303 three weeks ago while going up a hill on a trip,,,I changed the coil and all was fine,until she made the same exact trip today and threw the same code at the same place.
I told her when it started to shudder to turn off the overdrive and that cleared the problem up

if I already changed the coil,what else could be the cause of the same code at the same place?

 

Where did you get the replacement COP? The failure rate on aftermarket COP's is pretty high. It could also be a spark plug or *possibly* an injector.

 

Fouled plug maybe. Check the heater hose running above the #3 and 4 coils, there's a worm clamp on it that loosens, allowing coolant to drip onto the coils and cause misfires.

 

the COp is a Motorcraft part directly from the dealer and there is no leaking of the hoses near the area,,,cleared the DTC and it runs fine and normal,,until it gets to the mountains(very flat here on the SC coast),,,when it happens there is NO power,,she says she was even passed by an 18 wheeler going up the hill

I also noticed that when I use another scanner (hpertech) the code it gives is P7A00....not sure what that means,maybe the same as the P0303 i get with the superchip scanner

 

I agree with the above replies. I would go for the plug first- it may be fouled.

Then I might swap #3 coil with #1 to see if the fault moves to #1 - To confirm a Coil fault. That's not always a good idea , but in this case I would give that a shot.

Make sure you check those heater core lines good , a leak is hard to detect at times. The signs are - coolant in the plug chamber or a water spot on top of the Coil itself.