I had noticed a miss under load on my 2002 ranger 3.0 though it was fuel. Then a few days later I got a hard miss and a flashing check engine light. Got it home and code said 304. I pulled the plug and swapped it with another one I had didn’t change nothing swapped a wire no change finally got out the spark test and put it in the top off the coil pack for number 4 no spark. Put it in the top of of number no fire there. Replaced coil pack and wires and she runs like new. I think this might have been caused by a loose plug wire on number 4. Moral of this story is check your spark plugs wires ever so often to insure connection the connections are good.

 

Good troubleshooting, find, fix, feedback & to hear all now seems well.

If you stiill have the old coil pack, turn it over & check for case cracks underneath & carbon tracks to where it may have been arcing to ground unseen. Coil pack Case cracks underneath are a rather common failure mode it seems. Also ohm out the secondary winding between terminals 3 & 4, should be 13-15K ohms. Would be most unusual to be open circuit.
The primary winding will be 1 ohm or less, so would need a really good meter to actually measure its resistance, so it'll be really low but not open circuit, which would be most unusual