elkhunt22

Hi to all! I have an 03 silverado half ton and I am having trouble with my cold start. I start the truck which turns over like a top then it idles high at 3k rpms for several seconds then immediately drops and starts sputtering and occasionally dies if the gas is not applied. When I put it into drive it again idles very high around 3k. As soon as I brake or shift to neutral it starts sputtering again. Check engine light comes on occasionally but not when I go to test the codes. I was thinking it was a sensor but I am not sure. Anybody had similar problems? Thanks much for the help!