Heat gage goes from normal to hot and back

Could be the temp sensor for the dash, not the separate one for the computer.

SOUND LIKE THE TEMPATURE SENSOR IS BAD REPLACE IT WITH ONE THAT THE CAR RECOMEND. IF THE CAR ENGINE IS HOT :CHECK THAT THE FAN IS PRODUCING ENOUGH AIR THRO THE RADIATOR IF OK THEN CHECK THAT THE THERMOSTATE IS NOT THE FOULT.

have the cooling system checked for air lock
will be a gauge sender not a sensor

is it really because the engine is hot, sounds like a flaky guage of the temperature sensor under the hood is going bad

Your electric fan is probibly not running.Fan switch,fan relay or the fan could be bad.If it is getting hot and you pop the hood you should hear the fan running.

check the fan and water pump one of these is possibly ur problem when ur at idle there is no heat load and the radiator can dissipate that when ur driving causes more heat if fan isnt working the car wont cool same if problem is water pump at idle pump may be able to move some of the hot anti-freeze but when driving may not be pumping it thru radiator to cool

sounds like a blown heat gasket, very common on a 4.6

sounds like you have air bubbles in the system

U have a problem with the air temp control blend door actuator motor, very common failure. In order to replace this part the dash must come out.

should be fine as long as the gage goes up and down and you get heat it should be fine make sure you consider the outside temp. as the engine starts it will heat up get really hot the the thermostate opens and the gage will fall and should but not always stay low it could just be the ip gage.