In my 2004 F150 FX4, while going down hill and my cruise control set, the vehicle actually slows down, then lurches to catch up to the set speed, sometimes lurching several time unless I turn off the cruise control setting. Also, if I have a down hill followed by an up hill climb, the vehicle slows down, then lurches even harder once I begin up hill until the vehicle catches up to the set speed. Any ideas from anyone would be greatly appreciated since my local mechanic has no idea what's wrong.

 

Could be the speed control sensor going bad. Just saying that would be my first guess.