Could be the bushings in the 4x4 linkage. Nasty habit of coming apart and letting the linkage fall out. The one you looked at may have then worn enough that it won't go all the way in (not saying that is definitely the problem ) but something you can check easily if you don't mind crawling under the 'rango.
Idle could be the idle air control needs cleaning.
In the middle of swapping my '00 Durango 5.9 4x4 over to a 5 speed. I've been picking at it for almost a month now but every time I start on it, the skies open up. Thought I would get the trans out this morning but the bottom fell out as I was about to take out the last bellhousing bolt. (Working outside.)


Tim