IAC's are known for hating cold weather. Autozone sells them for $45.

As far as a high idle, is this when you're driving or when you first start the truck up? This sounds really stupid, but it has proven true many times. Ford Rangers and Explorers have a problem when it comes to distance between the brake and the gas pedals. If you are a member of the size 12 and up shoe club, then you need to watch your footing when you're at stoplights. It is very possible to have your foot halfway on the brake and halfway on the accelerator. I had this problem myself, and when I looked at my putting one time when ythe idle skyrocketed, I saw that my foot was halfway on the gas, and when I moved my foot farther onto the brake pedal, the idle dropped down.