2015 Ecoboost ignition problem
 

I have a 2015 F-150 with the twin turbo 3.5 engine. When I accelerate with a load going up a hill the engine starts to miss and the CEL flashes. The codes are P0300 (engine misfire), P0301, P0302, P0303, ( based on which cylinder is misfiring) etc. The dealer has replaced the all the spark plugs and the defective coil packs in the appropriate cylinders with out solving the problem. In two cases the coil packs have burned up and melted.

The engine has had the oil changed, and air and oil filters replaced. 109,000 miles, 6-speed transmission. 4X4 with locking rear differential, heavy duty tow package, skid plates.

It is going back to the dealer next week for a second time. What should they be looking for as I am not confident they know what is happening.

Thank you.
Frank 2015 F-150 3.5 litre Ecoboost