Ok so I am new to the site and just have a minor question that has been nagging me. I have a 2000 f150 4.2L. Within the past week I have give nthe truck a tune up.. all the works. My problem comes along the lines of changing plugs and wires. Upon tuning up the truck, took it for a ride and the truck ran great. Came home took about a 30 minute lay off and went outside to start her up. Well upon starting nothing but a misfire and rough running. So yesterday I changed the wires and plugs again and upon start up the same result ensued. So my question is what is the diagnosis of this. Ok yes i replaced the ignition coil pack, so that is brand new as well. My spark plugs come pre gapped as usual, also not a compression problem, i have checked all wiring as well and nothing is loose. I am grabbing a scanner so i can see if any codes come up, engine light didnt come up upon either times of starting the truck. So any help would be appreciated thanks.

 

most likely, you have a bad coil pack. {brand new.. but bad.}

If you still have your old coil pack, you can swap it out (if it wasn't bad before) and you'll know for sure.

 

Don't over look fuel maybe clogged or dirty injector