I have a 2015 F150 FX4 with the 2.7 Ecoboost with 18k miles on it. When I'm in driving around 45+ MPH and just barely get into the throttle, enough to gain speed but not downshift, the engine feels like it is misfiring. Ford didn't find anything wrong and went ahead and changed the plugs and purge solenoid. It is really noticeable going up any grade change. Anyone else experience this issue?

 

With only 18k, I doubt it's the issue but I'd suspect one or more coils.

 

If it isn't throwing a code, the odds of you getting any real troubleshooting are low. I would suggest pushing them to involve Ford for troubleshooting assistance. Not trying to beat up on the dealership, but real troubleshooting is almost a thing of the past at dealer level.