My 98 5.4 started skipping about a week ago. It only does it at very low rpm's when the truck is pulling a hill. If you give it enough gas for it to downshift, it cleans up. If you let it stay around 2000 or so it skips hard, actually making the truck buck a little. I put in a bottle of fuel injector cleaner and it seemed to stop. I thought it was a dirty injector but now it is back only after a day of running good. The truck has 69,000 miles and I am not sure if the plugs have been changed. If I change them, should I change the cops?? Could it still be a clogged injector??

 

Pretty common.

SEARCH keywords "low grade misfire"

 

Thank you, just what I needed. Funny, what the perfect words in the
search bar will find you.