Replace ignition coil and clean throttle.

I don't know if the idle speed is unstable or high. Normal cold start, in order to make the engine warm up quickly, the idle speed of the engine is relatively high at this time, and the engine speed will drop when the car is hot, generally above 700 rpm, which is a normal phenomenon; If the idle speed is unstable, there may be something wrong with the idle stepping motor on the throttle.