Doubt it's a low compression cylinder since I have no codes showing up. I did a live monitor and everything has checked out OK. I'm using an AutoXray EZ5000. It's a fairly decent scanner. I did notice this today and here's my thoughts. Tell me what you guys think. I was watching the temp gauge. To my knowledge the needle has always been dead center in the middle no matter what the weather or temp out side. It's winter here now so, it takes a while for the temp needle to get to the center of the gauge. When it does and I stop at a light the needle drops a significant amount. then goes back up after driving for a while. This is repeated at every stop. Also, the heater doesn't seem to put out the heat it used to. If this thermostat is sticking open wouldn't this tell the ECM the engine is colder so dump more gas in? That would explain the rough idle at stops and the poor gas mileage when it happens. Let me know what you think...