I think I have my own problem with my Aerostar. It is a 94 short E-4WD 4.0. I have only owned it for about 3 months, it now has 58,000. Since I bought it I have (New plugs, wires, PVC, cleaned MAF, changed all fluids, new thermostat, old one was sticking open, to try to correct idle problem replaced TPS and idle air control valve, after doing all this it idles alot better. The problem or wierd thing that it does is, it seems to not go into cold idle mode when it is started cold (sitting overnight) When I start it, it idles like it has just been driven. I have owned alot of fuel injected cars, and they always idle high for a little while when first started when they are cold. So I know this one should to. It still idles a little rough until it warms up. I have checked for vacuum problems, don't see any. Any sugestions, I am getting tired of playing (Which sensor is it game) (HAHA) Any help would be appriciated, can any one with the 4.0 let me know how theres idle when cold? I know this is not an Explorer, but I could use all of your knowledge on the 4.0 this is driving me nuts!!!