The wife had the Trooper out and it started to run rough and a flashing CEL popped up. She took it to Autozone and the guy said cylinder misfire #1.

At idle it sounds like one cylinder is not firing. The idle speed is not surging.

Thinking it was maybe a bad coil pack I swapped the one from cylinder #3 to #1 and vice versa (for those with other vintage rigs this vehicle has one coil pack per cylinder). Started it back up and it still sounded like one cylinder was not firing. Not sure if the problem had moved to #3 I unclipped the electrical connector to the #3 coil pack and the idle got much worse. Clipped #3 back in to return to the bad idle rather than the very bad idle. Then unclipped #1, no change. Conclusion - I don't have a bad coil pack or the problem would have moved to #3.

Pulled the spark plug in #1. It looked fine and was not loose like in a similar recent post. It has about 20k mis or less on it. Swapped it for another known good plug. The problem remains. Conclusion - the spark plug is not the problem.

Did a reasonably good check of the wiring, including the injector wiring, and for a vacuum leak using carb cleaner. Came up with nothing.

About the only thing left I can think of is a bad/plugged injector. This would seem to be a rare problem for the 3.5 engine though.

The vehicle has about 60k total miles. No recent work. Have about 1/2 tank of gas left (i.e. no recent purchase and the filter was replaced at the start of the year).

Did I miss something obvious? If you agree with the injector theory any pointers would be appreciated as that is a service I have not yet had to attempt.