I have a 2005 Ford F-150 King Ranch with 150,000 miles on it. I have changed plugs but when it is in a pull up a hill it has a miss or a jerk to it.
This is common to an engine misfire. The typical cause is a failing ignition coil. Since there is more than one ignition coil it is sometimes difficult to pin point. The engines on-board computer, given enough time, will diagnose this issue for you. Once the misfire is detected enough times in a row the check engine light will illuminate. Once the light has illuminate the computer has recorded the exact location of the misfire. Since there are eight ignition coils at over a $100 each, it comes in handy to know which one to replace. No damage will be caused while driving the truck until the light comes on but it may save you some money.
When combustion in one or more cylinders does not occur or occurs at the wrong time.