My 2004 5.4L pickup still runs great except for when I'm between 45 and 50 mph going up hill it will miss repeatedly until I give it more gas and it drops into the next gear than its fine. It runs great at 65-70 MPH on highway the check engine light came on but went back off one time. Any idea what it could be?

 

If you check engine like came on and then off, it threw a code that hopefully stuck in the computer memory. Go to the local automotive store and see if they can do a code read for you. That's a good place to start.

 

Possible computer memory issue? Purplehazeir is right, may be a professionals can reset it?