Its been sitting for about 2 weeks, since I've been on vacation, so I started it up to make sure there were no problems before I began body work.

It started up perfectly, I let it idle for about 20 minutes, then I went to turn it off. I turned off the key, pulled it out, but the truck was still running, very poorly. It sputtered for about 45 seconds then finally stalled out.

What could cause this and how do I fix it?

Thanks!