Hi guys, I'm new here and have been reading on forums all morning trying to figure out what is wrong with my truck. The truck is a 97 4.2L with 5spd Mazda transmission, recently the engine blew a head gasket and blew the engine so I just completed a swap from a 2000 f-150 4.2L with minor adjustments in the wiring and a couple sensors. Anyway here is the problem the engine ran fine in the 2000 but when i swapped it over into the 1997 body it now has a misfire at idle and under load. I replaced the fuel filter on install, checked the plugs and cleaned them before installing and all appeared to be in order. Now I don't know how the truck ran before the head gasket blew as it was under different ownership at that point so I'm not entirely sure if the coil pack is any good. Any input on this would be great it is booked into a mechanic later on in the week.

Thanks.

 

First things to look at are plugs, wires, and coil pack.

 

Yep, as you said, plugs and wires and shes back to running like new. Thanks for the input