Here's one of those strange electrical issues:

A couple years ago, my ma's '98 needed a jump. The blasted thing wouldn't idle once it fired, even after changing the battery at the Wal-Mart (I didn't leave that thing in there long and got a real battery). I pulled the air filter out and it ran fine, idle and all so I replaced that and it fixed the issue.

It wasn't throwing codes or anything of the sort, so it was a tried and true "guesswork" fix.

Also, have the Dealer hook up the pressure gauge to the fuel rail and check the system for irregularities. When was the last time the fuel filter was changed?

 

The fuel filter on these trucks in in the fuel pump unit itself.. they dont commonly go bad but, in order to change them you must drop the tank and replace it as a whole fuel pump unit.

 

I'm learning as I go here, so random questions from me will die down as I figure everything out.

I do recommend having the fuel pressure tested though, just to eliminate that as the cause.

 

Well it seems that it was the PCM indeed! I had the dealership replace the original one, and now the Durango runs like new again. $1200 total, that's with the tune-up and fuel injection system clean that wasn't the cause of the issues.