I have an '89 4.0 Cherokee Pioneer. I have been having an idle problem for some time. Sometimes, first thing in the morning, or after work on my way home, when I start it, it will idle way up at 2500 rpm for a while until I shut it down and try again. Sometimes (usually in the summer) parked in the hot sun but a cold engine, it will start fine, but when I go the idle will be so low it will stall, this is very annoying, it will be stalling one minute and the next minute it I am idling about 1800 rpm, coming to a stop sign I have to really press hard on the brake (or throw it in neutral) and sit there like a moron with my engine revved up.
I have taken it twice to my works mechanics (commercial) over the past years and they did something to it that worked fine for a year then the problem came back. I have a new vacuum hose harness. (but some hoses are old)
Richard