1993 E150 Idle Problems

I have a 1993 E150 (302 motor 5.0 V8) that has been sitting in my boss's driveway for a couple of years. We replaced the spark plugs to get it to turn over. It will run with the gas pedal down, but when you let off the gas it shuts off. It has been about 10 degrees ferenheit or less since we started to try getting it to run. Everything works fine, it just won't idle on its own. The boss says it just needs to warm up and work out its kinks. I'm skeptical though! Any thoughts?