I'm having trouble with my 1999 F-150. It's idling and running rough, due to a misfire on cylinder #4. I have a 5.4 Liter Triton V8. I recently replaced the COP assembly and spark plug, but no luck. Do you think it could be the fuel injector? Any ideas? I am a DIY home "mechanic" with minimal experience.

 

Was there liquid in the well? The heater hoses are noted for leaking there.

 

What cop and plug did you install?
That is one of the toughest one's to replace.
Make sure you got the boot seated properly and feel it snug over the plug. It can kink in the plug well and make you think that it is on there when it is not.
Also, like mentioned, that is the cylinder that is most likely to take on a water from a heater hose leak or rain water.

 

Did you use dielectric grease in the cop boot?

 

I had the same issue with Cylinder 3 and it was water in there. I replaced the coil and boot after letting a microfiber towel sit in there for an hour or so then blew out the well is compressed air. Not sure if that's even smart to do but I haven't had the problem since.

 

Compressed air is the best way to get any debri or water out. Or you can attach a small suction hose to a vacuum. But I would use air.

 

Thank You all, I had a local mechanic take a look for visual inspection. I worked with him to determine that the coolant hose was loose, and had been leaking copious amounts of coolant into cylinder #4's COP assembly. We had to pry out all the bits of rubber boot for 3 hours, and eventually cleaned out the well and replaced the coil, Good as New!!!