My engine idles at 1000rpm, all the time. When cold, a little higher, but that's expected. After warming up enough, it drops to 1k again. I had a smoke test done and no smoke came out from anywhere it shouldn't have, so it's not a vacuum leak that I can tell. I've been told it might be the Throttle Position Switch, or that it might just have to be adjusted. Could there be any other culprits?