Lately when I start my truck in the morning or after it has set for a period of time, it will rev to what I would say about 2000 rpm (I don't have a tach) for about 5 seconds then back down to high idle until it is warmed up. Is this normal, or is there something I should investigate?

Thanks,

 

they always rev a little higher at first start up.

lived in WI all my life and EVERY single vehicle i cold started has done this. youre golden.