Hello, I have a 1998 F150 4.6. Last spring I changed plugs and wires because it was running very rough. This fixed my problem at that time. So my truck has fairly new plugs and wires (Ford Motocraft). I am now getting a check engine light and the code is a PO300. The truck is running fine. I don't feel a misfire. I am told this is a random misfire. The only suggestion I have gotten was the coil packs. Does anyone have and details on this code and how to diagnose so i am not randomly changine parts. Thanks, Anthony

 

That's a RMD code = Random Misfire Detected -

1. Wires

2. Plugs

3. Coil Paks


Go thru it in that order and replace/clean components as needed.

Sounds like a coil pak is getting weak , maybe not .. Try pulling the wires and goop some more dielectric grease in there and spray some silicone on the wires to seal them up good. Disconnect the battery first.

 

Did you run your truck very low on fuel? I did with mine on accident and I got a P0300. Filled her up, cleared code no trouble.

 

Don't overlook a fuel delivery problem. If you can get to a scanner with mode6 you can see which cylinders are misfiring and their counts.

 

Jbrew... you forgot option 4. Change fuel filter.. It worked for me.

 

Thanx , yea , I left a few out - must have been in a hurry

 

un hook the battery and let it clear the code. and see if it comes back.