I have a 97 F-150 w/4.6 engine w/ 163000 miles it has been great it uses no oil between oil changes and has always ran strong but recently it started to develop a miss after the engine would warm up and at first it was sporadic but now it occurs on acceleration or any time it's under load and the service engine light starts to blink. I plugged in the Actron scanner it the only code I'm getting is P0303 which of course is cyl. 3 misfire. I changed the plugs and wires at 100k miles as per the manual. I figured since I don't drive it much that maybe a that fuel injector may have gotten dirty so I put in 5 gallons of high octane gas and a bottle of Lucas injector cleaner and took it for a spirited ride and it seemed to kind of smooth out but every time I would accelerate at an intersection it would do it again. To make a long story short this particular problem usually calls out: bad fuel, bad spark plug,bad spark plug wire or bad coil and my question is since this engine has the EDIS system wouldn't all four cylinders on that bank have a problem? These issues usually require changing all of the above before it is corrected anyone run into this before?
Thanks Y'all for any input on this matter!

 

It could very likely be a cracked coil where only one cylinder would be affected. You can swap the 2 coils and see if the miss changes cylinders.

 

Check for moisture in the plug well. check the heater hose clamp and connection mine used to leak after a hard run and get into the plug well on the passengers side or very wet conditions . I would blow out the plug wells with compressed air and all would be good again.

 

I am having the same code P0303 and was wondering if it makes any difference which coil of the four I swap #3 to?

 

Post deleted