I have a 2001 Chevrolet Silverado I start it in the morning and it idles real high then it will idle real low and it will either die or if it catches itself it will idle real high again once it warms up its fine the service engine soon light will come on sometimes any ideas what's wrong

 

I'm guessing your intake gaskets are bad causing a vacuum leak until the engine warms up. You'll need a tech2, or to be brave and go outside when it's cold, and the truck has sat for a while. Start the engine, and pour a cup of water on the intake where it meets the cylinder head. If the engine bogs and sounds like it made a sucking sound, then you've got bad intake gaskets.

It's so darn cold though, I don't know if you'll be successful without creating ice.