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On my 99 expy, 5.4 (66K miles), I have encounterned rough starting in the very cold Nevada mornings. I would have to crank the engine 3 to 4 times to finally get it to start. When it catches, it sputters for a second or 2 then idles fine and drives fine. It is also doing this after it is warmed up as well.
It could be the IAC, take it off and clean it, and see if that is the problem. I don't think it is, because the IAC usually causes rough idle, for longer than 2 seconds.