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.

 

Did you disconnect the battery at any point? If you did, it shouldn't backfire but it will run rough until the ECM gets enough data from the various sensors to average out the input and it straightens out. That usually happens around 50 miles. And while the coil packs may be new, there can be failures out of the box. There should be a testing procedure here on the forum.

 

If you got a misfire, was the check engine light on solid or flashing when this was happening ?

 

new fuel pump, scanner says theft & light is flashing but it cranks over fine will start on death but no fuel pump during crank any ideas

 

The theft light is flashing while you are cranking the starter ?

This means the key you are using is not showing as programmed for the truck, try another key.

Until you get the theft light to go out, don't waste money replacing other things.

Turn the key from off to run ( do not start ) does the theft light go out ?