2007 F150, 54L with 220K.

Back in the spring I noticed the truck would jerk, hesitate and stumble while driving, but mostly under load when at low RPM's, and then would clear up after RPM was gained. At first I thought it was tranny problems, but CEL never ever did come on, so I never put the reader on it. It wasn't a common problem, just occurred once in a while. Over summer it ran pretty well.
Fast forward to today (-30, of course) and the problem has gotten worse. On my Xmas trip I was bucking a pretty good head wind and the stumble and hesitation got worse. The check engine light finally flashed for a while and then quit. When I put the reader on it, it flashed the engine code P0301 - which is a misfire in cylinder #1. It comes on all the time now that I am back at home.

From what I researched, this code can be caused by any number of things.

Here's what I've done so far. I swapped the #1 and #2 coil packs and I get the same error code, only this time it has a "P" at the end. (P0301 P). So I don't know what the suffix P means, but at least it rules out a bad coil pack. The plugs were changed a couple of years ago and only have about 60K on them. It may be possible #1 plug is bad or weak, but with so little mileage on it?? The stumble or hesitation only comes when the truck is under load at lower RPM's.

I'm looking to see if anyone else had similar problems and what the common fixes were. From some of my research and what I have done so far, I'm wondering if something may be wrong with the catalytic converter??

 

Depending on what style of code reader you have, the "P" at the end of the code could mean Previously active. If you swap the coil pack and run it for a cycle and the code dosent go to a new cylinder. If it does stay at #1, i would pull the plug and just check it. Could be a injector but rare. I had this same issue with my 02 Mustang with the v6. Replaced the coil pack and all was good.

 

The p at the end means it is a pending code. Which means it is not active as the cylinder does not have a constant dead miss. I would suggest changing the plugs out for a fresh set and go from there. You have eliminated the coil by swapping it. It could also be an injector, but see if that you said the plugs have roughly 60k on them, I would start there.

 

Cracked or defective spark plug...sometimes caused by a defective coil pack.

 

Sure enough, cracked spark plug... actually part of the tip was broken off as well. The boot needed replacing too. Now she runs like a top again.
Thanks all.