What is the reason for the unstable idle speed of the cold car?

Hello, the biggest doubt in basic judgment may be related to the throttle. This fault has nothing to do with transmission oil, brake oil and coolant.

The throttle of modern vehicles is different from that of the past. The previous throttles were all mechanical throttles. When idling, the throttle valve is completely closed, and the air is transported by a channel next to the throttle valve, and there is another valve in the channel to control the air flow (idle control valve). Usually, even if the throttle is dirty, it rarely affects the stability of idle speed. Only if there is a problem with the idle speed control valve will there be a fault.

But now cars are all electronic throttles. When idling, the throttle is actually slightly open. This will minimize air flow. If the throttle is dirty, it will easily lead to unstable idle speed. (Originally, only a narrow gap was opened. If there are carbon deposits or oil stains on both sides of the narrow gap, the control accuracy will naturally fail. ). At this time, the problem can often be solved by cleaning the throttle once.