Re: 2002 f-150 5.4l jerking/backfire
Looking only for codes won't do.
They have to use a Scanner that will go to 'non continious monitor', then step to test 53, then step from cylinder 1 through 8 and look at he missfire count result.
If they don't know what that is, then they don't know how to do anymore than look for codes.
You have an issue that requires deeper diagnostics than just codes in order to get to the cause of your issues.
Ford has provided near full ability to access operating data for this use or a dealer could not service there own vehiches in shop.