02 trailblazer revving really high at times

[slimnottygirl]

I own a 02 trailblazer and it just started revving really high when it is cold. I live in canada so it really isnt that cold right now but when the temp gauge is at 40 due to the truck sitting for a while when i start it and when i drive it, it reves really high once driving it and the odd time if you give it a shot of gas it will lower revving but it is really loud when i first start out.