I've been having a probem with my car now for a couple weeks where my car overheats when I slow down or stop, then starts to blow out cold air, while the temp gauge goes up in the hot zone until I start moving fast or rev the engine quite a bit. I changed the thermostat, and checked the antifreeze level already so thats not the problem. Also, just recently my check engine light came on with an error for the knock sensor. Are any of these things related? I need help I'm really frusterated with the problem. Any info would be greatly appreciated.