2008 Ford F150 w/4.2L V6 Auto, 16K miles; when driving between 45-55mph, truck shudders during mild acceleration; the problem goes away by applying more gas/harder acceleration, or by switching the OD to OFF and getting higher revs. Sometimes the truck will backfire while slowing and making a turn. Suspect ignition problems (coil pack, plugs or wires). Have unplugged both ends of plugwires, cleaned and reseated, and prolem is hard to duplicate now. Need advice on next step?
Tags: 16k, 2008, 4555mph, auto, DRIVING, F150, ford, miles, shudders, truck, v6, w4.2L