My '99 XLT (4.0 & auto trans) with 95k miles has started idling fast
-- about 1500 rpm in neutral or park -- after it warms up (normal idle when it's cold). It does not run rough. The second part of this problem is that the engine runs hotter than normal - though it never gets into the "red" zone it gets warm enough to cause "strange" shifts. There is no water in the oil, or oil in the water. I don't hear any obvious vacuum leaks around the front end.
Browsing past posts, the IAC seems to catch the blame for a lot of the idle problems, but nobody has mentioned an elevated temperature for the IAC.
Any ideas are very welcome.
Mark Sparge