Ford Repair: 2002 Ford Explorer keeps dying, throttle position sensor, air control valve

Question
My 2002 Explorer keeps dying on me. It is always when in drive and stopped or slowing to a stop.  When sitting at idle in drive, the engine has small surges up and down and will almost die many times, then catch again. Then the next time, it will die.  Runs better when the air is running at 3 on the fan.  It is a 4.0L SOHC Flex Fuel 6 cyl, 5 speed auto., 54,000 miles.  A friend's husband changed some kind of sensor on his explorer that fixed his problem.  He can't remember what the sensor was called, but was cheap and easy to replace.  Any ideas what is causing the problem?

Answer
The dying sounds like a dirty idle air control valve.However, the surging indicates a throttle position sensor.Have the trouble codes pulled at your local parts store. It should be a good indicator of which sensor is defective. While you are there, buy some Air Intake and Throttle body cleaner. You will need to clean the throttle body with some elbow grease, and a cotton towel.