Guess I'm still learning my way around the 4.0

[TrexMex]

After checking a TON of threads that have to do with idling, I finally found out that 900 RPM is a normal idle value on a manual 4.0.... or at least that's what it says here: http://www.therangerstation.com/forums/showthread.php?t=44509

I still have the RPMs intermittently dropping and going up between 600 and 1000... I did the IAC valve test (unplug it with engine warm and see if engine stutters/dies) and nothing happened so I guess I need to start there..

Any suggestions are more than welcome

 

[Kona]

My 91 4.0 idles around 800 - 900