Finally threw a code. It was being intermittent, only appearing when hot and above idle, with no codes. Now there's a misfire on cylinder #10, of course. I'll pick up a new coil pack tonight and hopefully that will be the end of my woes.

 

Your coil may be fine.
You might try changing just the boot/spring - NAPA 702418 or Dorman 49812.
The boot/springs are under $8.
Pull the COP and check for a rusty spring, splits in the boot or cracks in the coil housing.

 

You can also move the COP to another cylinder (one easily accessed) and see if the misfire code follows.

Stewart

 

Good point.
Also, if the misfire code does not move you may have a:
bad fuel injector
broken wire in the COP connector cable
broken wire in the fuel injector cable

 

That's a good point, i will try that. I just assumed it would be the coil pack because it started after driving through a massive puddle which came up over the hood.

 

You probably just have moisture down in the plug hole.
Blow out the plug hole with compressed air and pull the coil/boot off to see if there is any water in it.
I had rain water dripping from the panel at the base of the windshield causing misfires on #6 & #7 in an Exped.
Sometimes got a code, sometimes not.
Fixed the drip, dried out the plug holes and my problem was gone.

 

If you wanna cover your bases, you can swap the COP to another cylinder, and swap the COP boot to another, different cylinder.

COP boots are a heckuva lot cheaper than the whole coil.

Stewart

 

Pulled the COP and it was not just dripping wet, but also had mud, rust, and dirt. Cleaned that out and cleaned up the coil pack, but sadly that didn't fix it. Pulled the plug and cleaned it, and put it in #2, and put the coil pack in #2, and put the plug and pack from #2 in #10. #2 started to misfire.

My father had stopped by when I started it, and he said it's running fine. I could still feel the misfire so I plugged the computer in and saw #2 code. He said anyone else in the world wouldn't be able to feel that, as it was pretty subtle when you have 9 cylinders that are running fine.

Reluctantly replaced the coil pack and fired it up, and my issues were no more. Held on to the coil pack just in case. #10 was pretty easy to get to compared to #8 on my v8 expedition years back.

All is back together and all is well.

 

Glad to here you got it sorted out

Ford released a TSB quite a few years back, advising dealer techs to NOT replace COPs because of a misfire without testing them, because of all the COPs they got back and inspected, some huge amount were not bad, something like 80 or 90% of them.

Be that as it may, you fixed the problem with a new COP. Carry on