Ok haven't been driving my disco lately because it developed gradually an erractic idle that eventually became bad enough that it would die almost every time I stopped. I have put a few new parts on such as fuel pump, filter, intake manf. due to crack, injector seals, performed numerous vacum leak test, tested the temp sensors all to no change in performance. Today realized there is one more temp sensor on the elbow of the thermostat housing that tested open no resistance. thought that was the prob so subbed in a resisitor to trick the computer to think it was at proper temp no luck. Remembered that I had checked the timing and set to 6 btdc and not tightened it down. In moving the dist. a little starts running smooth and holding constant idle at 800rpm. checked timing it was at about 8 atdc. This was extremely odd but the truck runs great and if you put it back to 6btdc it runs rough again. Is it possible that something has slipped some where. First thought was timing chain slipped but I just replaced it 20k ago and it has run fine since then. Any insightful ideas would be appreciated. Thanks Daniel