over heating

Hello everyone! Thanks in advanced for taking the time to read and for any veteran advice you have. Jeep liberty 2008 3.7L V6 214,0114 Here's the issues I've observed: temp gauge overheating while idling but immediately goes back down when accelerating but not if the ac is cranked...

So that's it, the car will overheat but the temp gauge stays right in the middle and doesn't show overheating. I've replaced the thermostat and the fan motor but still overheats. There are no codes saying the PCM is bad. Thanks James