alright, buddy owns a 2000 f150 4x4 with the 4.6L.

he started out with a misfire and set to do some maintenance on the truck. first started with wires and plugs, still misfire.

he changed the coil packs, still misfire. got code read, p0302. pulled wire, very very nasty in there. cleaned everything out, put plug back in. still misfire.

the first plug change he used autolites. i told him to go buy some motorcrafts. did a complete plug swap again, cleaning everything thoroughly as he went along. the truck still has that same misfire.

so, brand new plugs, wires, and coil packs. dont know the exact code but he is getting an insufficient egr flow. i told him to get a new dpfe. he still hasnt done that but i dont think it's related.

any other suggestions in relation to the misfire? oh, very slight miss at idle, gets bad under load, and pulling the wire makes things worse.

 

I would try and switch the injector form the missing cylinder with one that is not. Disconnect the battery, and, then wait for another code. If it changed, then it is a bad injector.

From the symptoms you describe, it very well may be the injector.

Also, be sure that you are using dielectric grease on the plugs and wires. It will sometimes cause a missfire if not used.

Let us know what you find.

Good Luck!

 

would it still be an injector since removing the wire made things worse?

i made sure dielectric was used the second time he did it.

ill get him to switch injectors next time i see him.

 

Pulling the plug wire, and, things get worse just means your plug and wire is working. This does not test to see if the injector is stuck open. Pull any wire on any cylinder and it is going to get worse.

You have made sure the spark part of the formula is working, now you need to go to the fuel portion.

 

youre right. dont know why i didnt think of that before.

appreciate the help. will update.