KIA Maxima 1.6 automatic transmission is unstable at idle speed. What is the reason

What is the reason for the car's unstable idle speed, up and down? 1: The internal energy in the system is reduced due to the failure of the ignition system. 2. Air leakage in the intake manifold will lead to unstable vehicle speed. 3. If there is too much carbon deposit on the accelerator, the idle speed of the car will be unstable. 4. The fuel system failure leads to unstable idle speed of the car.