Hello,
I noticed you have some great info on idle problems, and was hoping you (or anyone else who knows) could help me with an idle problem I've got with my 1990 2.6 4ZE1 : The problem is directly tied to outside air temp. When temps are high, say above 75-80, my trooper has a very low idle (and will sometimes die) on COLD start up. The low idle is worse the higher the outside air temp. After the engine has warmed up for only a minute or two the problem goes away and the idle speed is fine. If I restart the engine WARM there are no problems.

I bypass this problem by immediately switching on the AC as soon as I start, and the idle is fine. I have had this problem for a long time, and no one seems to know what causes it. I have heard from other troop owners with the exact same problem. In the cooler winter months on a cold startup the engine does fine, with idle immediately kicking up to 1500 rpm or so before dropping down once warm. This problem ONLY occurs in warm (especially hot) weather on a cold start. Sorry for the somewhat long post. Any help/advice would be MUCH appreciated. Thanks