I own a 1998 Expedition XLT with 80K miles. The vehicle often wants to idle at 1,500 or 3,000 rpm (depending on it's mood, I guess) while driving. The problem is most notable in warm or hot weather, and almost goes away when it's very cold out. I replaced the idle air mixture unit (proper name?), which fixed it for about a week, then the problem resumed. Secondly, the vehicle's front heating system is very weak - it will take 1/2 hour at full blast to make the driver even remotely comfortable. The rear unit appears to function normally. Could these problems be related? I am very limited on $ and need to keep this vehicle for a long time, but these problems make it very unpleasant for me and the kids to ride in. Any and all help is GREATLY appreciated. Jim