high idle sometimes

I have a 1995 S-10 with 4.3L W CPI. I have been noticing my idle is hi (1300 RPM)when I would come to a stop but not every time. I own my own scanner and there are no codes. The hi idle is coming from the IAC 37 counts. It should be around 12 with a/c on. Something else is weid is my Knock sensor reads 200 +. when it hi idles. I have played with the a/c switch to take the load off but nothing happens.