Tahoe issue??

[THEFERMANATOR]

You will know REAL quick if it is the throttle body carboned up. The colder it gets the worse it will be. When the engine is cold it needs more air, and if teh throttle body and IAC are carboned up it cannot get enough air in. Think of it like a choke on an old carbed engine. If the throttle body is carboned up, then the choke essentially can't work to allow it to stay running. If it doesn't want to stay running, give it a little throttle right after it starts to keep it running. After a minute or so it should idle on it's own.