Is this a thermostat problem, when im idling my temperature goes to 3/4, the fan turns on and stays the same, i start driving and my temp drops to normal, coolant is full, the engine is d16z6

 

When in doubt, change it out!

That is what it sounds like to me. Next time it starts to rise tap the gas and spin the motor up to 4k. Just a tap of the pedal and see if that will make the temps drop. Try it a couple of times. What it will do is put more water pressure/vacuum behind the t-stat and pull it open. If this does work then it is definately the t-stat.