Ok, I'll keep this brief, was hoping someone may have some info to help me...? 01 F150 with 4.6l engine.
I replaced all 8 plugs and all 8 coils about 20,000 miles ago, to fix this very code. It went away for about 15k and then code came up again, same coil. Threw another coil in it and it went away until about 2 weeks ago. At which time I threw another set of plugs in it (didn't need them, but I did anyway) and ANOTHER coil on #4.
Today on my way into work...of course, skipping and threw the code AGAIN! I've checked the wiring out to it, and made sure it wasn't a loose connection, it's not. Wires not cracked/shorting that I can find. I looked quickly at the grounds, to make sure they're tight and they appear ok.
I just swapped #4 with #1 to make sure it's the coil, need to drive it and re-read codes to make sure, but i'm fairly sure it's going to have moved to #1 bad coil.
Before I put yet another coil in this truck, is there any reason for these to be going bad again and again?? Is there something else causing this that I'm missing? This is getting expensive and frustrating.
FYI always use motorcraft coils, no cheap junk ones.
Thanks in advance

 

Have you checked the area around the coil for any moisture or more importantly coolant when it's throwing the code? It could be getting some coolant and or condensation dripping onto it which is a common problem with #4 coil

 

I didn't see any moisture/coolant on it. I just swapped the #4 with the #1 and everything was dry. Reset code, ran up the road a few miles and back, and code came on. It's saying #1 coil now, so it went bad for sure...again! Why does that #4 cylinder coil keep going bad? It's weird for sure.

 

I vaguely remember reading something about a line dripping water onto the #4 coil but can't for the life of me remember the details of it right now I'm sure somebody here can fill in the blanks

 

On my truck, the heater hose just above #4 would release a bit of coolant, which dripped down into the plug well and would crap out the coil. All this was a random occurrence. Recently I added a gear clamp in addition to the original clamp, and I've got my fingers crossed that it's stopped. But it wouldn't be hard to replace the hose, or trim the crappy end off and reconnect, if you have the length.

 

Open the hood and run water down the windshield. The weatherstripping above the #4 coil came loose in my truck and let water run down into the engine compartment and drip right on top of the #4 plug. The weatherstripping looked fine, but still let water in. Hope this helps.

 

It most definitely a moisture problem. Now you need to find out where it is coming from

 

Thanks for the help! I'm going to get to the bottom of this. I was thinking, I didn't see any moisture, BUT I live in Colorado and it's really dry here - moisture doesn't hang around for long....maybe just long enough to short out a coil and evaporate I'd say! I'll be checking all the hoses around there AND the idea about it running down the windshield. I hadn't really thought about it before, but I know this time it went out 1 day after washing the truck! hhhhhmmmmm....

 

GOT IT!! Thanks CKing, my truck was doing the same thing yours was! I opened the hood and hit the windshield gently with the hose, the weatherstripping was leaking water down on the back of the engine, and onto the #4 coil. I didn't realize it, but I'm thinking when I washed it there was most likely water leaking in there and ruining the coil. Because it's so dry here/the engine gets hot, the water would evaporate and I never saw it. I'm fairly sure that's the problem though.
Thanks to everyone who replied to help me!!