My 02 4.0 has an erratic idle at idle only...does not miss under load or acceleration. not plugs or wires, cleaned the throttle body...any ideas

 

I would clean the MAF with special electric cleaning spray.
Have you ever replaced your fuel filter?
A dirty fuel filter may cause this.
Also, check/listen for vacuum leaks.
You may have a vacuum hose that came loose.
Good Luck.

 

2001 and up 4.0l SOHC Rangers had an issue with PCV valve hoses, they would crack at the elbows, under side so you can't see it, have to lift it up to look.

Wowmike has some pictures here of what to look for and a good fix: https://www.ranger-forums.com/4-0l-o...mon-cel-93776/

After engine is warmed up, unplug the 2 wires on the IAC(idle air control) Valve, that sets engine idle.
Idle should drop to 500rpm or engine may even stall, either is good, it means no vacuum leaks.
If idle stays higher and/or up and down then start the search for the vacuum leak, you got one