My 2002 f-150 surges or jerks at speed between 45-60 mph. Could this be a overdrive problem or something else? In the past my mech. just changed 3 sparkplugs that were bad. They were new but there were 3 defected ones.
Problem still there. Anyone have any ideas?

 

What engine are we talking about?

 

Yes, and what transmission? And is the symptom constant or intermittent? And has the CEL come on? And if it has, have you run a scan to see what code(s), if any, is(are) being thrown? (We may not have any answers, but we surely do have lots of questions.)