my cars temp gauge is pretty much always cold, but somtimes and i mean like once or twice a day it will get to the mid range between H and C.
could air in my coolant system mess the reading up too? i know that the idle air control valve uses coolant to tell the ecu that the engine is warm right? so that might be why i have problems with it keeping idle when its cold?

 

when i had my temp gauge problem it was because i needed to replace my thermostat, my car kept reading it was cold while the car was in motion, knowing damn well it was normal temp, maybe you should look into replacing your thermostat.

 

if the thermostat fails, depending if it fails open or closed, if it is open, the coolant will continuosly circulate threw the radiator and be cold all the time and the sensor wont pick it up. See if you get heat into the car when it is running for a while.