2000 Jeep Cherokee Sport 4.0 Low Idle Problem

Hi I have a 2000 XJ sport 4Liter. Recently, I started having an on and off problem with low idling when the jeep is stopped. It runs fine when in motion and in gear but when i come to a stop it will idle at uncomfortably low rpms. It does not make a difference if I am in gear or not. As the problem became more frequent I noticed it will start and idle fine but as the engine heats up the idle will drop. I already threw a throttle position sensor at it because that code came up on my reader a while back but went away. The new TPS did not help the problem. Also, there doesn't appear to be any blatent vacuum leaks. What else should I be looking at?

Thanks in advance for your help.