Car starts, but won't stay running.

What is your question?

Brand new battery and alternator. Car will start, but slowly idles down until it shuts off completely. A friend who replaced the alternator thought it could be the electronic throttle? Said something about it being "gummed up", that it might need a cleaning. Does anyone have any ideas of why a car would start but not stay running? It seems like it would stay running if I constantly was revving on the gas, but if it's allowed to just sit and idle, it eventually shuts off. Yes, there is gas in it. ;o) Thanks!