I have a 2002 Ford Explorer Sport Trac 2wd 4.0L with 75,000 miles. Within the last 5 days my engine light has come on, and it will not idle properly. Once it goes below 1000 rpms it cannot maintain an idle. The rpms will fluctuate between 800, 1000, 500, and lower until it stalls. If I keep the engine at over 1000rpms while stopped it will not stall. At higher speeds and rpms there does not seem to be a problem. The only other thing I have noticed, is that it seems a little sluggish when you hit the gas. Do you know what might be wrong?