When my IAC was acting up, it just wouldn't run if I didn't have my foot off the gas. It would just stall out at a stoplight ir whenever I took my foot off the gas. I'll tell ya, that was tricky trying to brake to a red-light. Too many pedal's, not enough feet! I was able to clean it up and it hasn't acted up since then.
When my o2 was out the way out, it would idle eratically. I would just try un-plugging the o2 sensor and see if anything changes. Have you checked your codes?
1992 4.0HO 5spd -- BDS 3.5" lift -- 33x11.5 M/T's -- Gibson Cat-Back -- 8.8 with 4.10's -GONE
1967 FJ, linked, 350 chevy, 35's, arbs, blah blah...
"If you're not moving ahead, you're falling behind"