Car Shut Off While Idling Wont Start

With our improved gas and highly improved oils, wear, for most engines, is not an issue. The truck wont start unless i press on the gas pedal as I turn the key, even then it still shuts off every once in a while while I'm idling whether at a stop light in drive, or in a parking lot in park. Last night I was on I-95 south bound doing about 65mph in my 2002 Chevy 1500 4x4 4. The engine tried to turn over, but it didn't start. Once you get the car running, let it idle until the temp gauge is half way (operating temp) and then adjust the screw until you have a grey exhaust smoke. It goes black>