Misfire need help !

[Esat]

I'm at 163k on my Gen 1. No injector issues. Just timing chain and turbo manifold. But I use top tier fuel so YMMV. It's not something I've heard mentioned frequently as being problematic on these engines. My misfires were plug gaps and the towel incident. I haven't even changed my coils.

Check the plug wells for oil too. The plastic valve covers leak eventually and oil will get into the well.

Also if you find instead of oil, coolant,this calls for intake manifold replacement like mine. In front corner side rubber gasket getting old and starting to leak coolant, that goes in to the holes of plugs and causing misfire.

 

[GaryH]

Have you run an OBD II test on it?

 

[LokiWolf]

Sounds funny, but stick a flashlight up the tailpipe and look for insulation. My muffler came apart internally and plugged the tailpipe with the fiberglass insulation and caused a misfire on cylinder #6. This happened to me while towing our RV. Looked like a dead animal was stuck in the exhaust pipe.

Yep, this has been an issue in the past!

I will just add that I think OEM motor craft plugs manufactured after 2021 turned to crap. I changed my plugs with motor craft plugs bought from autozone (not Amazon), and started having misfire issues. Took to dealer, and they said my plug was bad(had less than 10k miles on em.)

YES! Complete crap!

Re: Injectors…
Techron fuel system and injector cleaner has been my gold standard in my 5.4 and 3.5 Expeditions for nearly twenty years.
The 2003 5.4 went 262,000 miles and ran great other than spitting out three spark plugs (Staked inserts) and new Motorcraft coils, when I traded it in for the 2015.
It was a total Northern Indiana rust bucket but ran great.
The 2015 only has 132,000 miles on it with no problems so far.

Techron is an EXCELLENT option. I would have recommended it also above but the RP was one sale, and also GREAT stuff.

 

[James3336]

I have seen issues with coil connectors. If all else fails try replacing the coil connector itself.