2010 F-150 5.4L - started having intermittent misfire several days ago, then yesterday it started to get bad under acceleration and check engine light started flashing. Drove to Autozone and had the code read which indicated ignition issue P0305 which is on no 5 cylinder. Changed plugs to no effect, changed coil to no effect, changed injector still to no effect. It appears to be when load is applied although occasional misfire at idle. When running at constant speed smooths out but any change to throttle, starts missing like crazy. Fault still shows P0305.
Suggestions required for next move. Mileage is 224k

 

https://www.f150forum.com/f38/ 2009 to 2014 f150
This is the link in the forum for your model year. May get more answers there.

Maybe check compression on that cylinder.

 

More frustration.