Check engine light on 2003 Ford Explorer Sport Trac

check engine light is now on, vehicle does not idle very good, will even die at times.....vehicle runs great down the highway.

2 answers
I'm not a mechanic, but I would get a fuel system cleaning and have the run a computer diagnostic on ur engine.
You probably want to have a diagnostics check done, but I was experiencing the same problem and it turned out that one of my vacuum hoses had a leak. I had the hose replaced and it has run great ever since.