just picked up a 1990 xj for 600 bucks a few days ago and I am trying to get everything working 100%. The one thing I cant seem to put my finger on is the low idle. There is no issue with stalling, however she idles anywhere between 200-500 rpms. There is no issue with acceleration or anything just the low idle. Its the 4.0 renix 154000 miles.

 

i just got a 90 xj and its got 400+km on it and it idles arround 300-500 but never stalls or give any prob i think it might be the tac

 

I have an '88 XJ that does the same thing most of the time. I think that it has to do with which day of the week it is LOL, its pretty random and the jeep runs fine anyway. 231000 miles!