What is the reason for the high idle speed of hot cars?

The reasons can be roughly divided into three categories: excessive fuel injection, excessive idle intake, or incorrect engine control signal.

The common reason is that there is something wrong with the throttle. Throttle is called the throat of an automobile engine. Because the throttle is connected to the air filter and the engine block. When we step on the accelerator pedal, we actually control the opening of the accelerator instead of the amount of gasoline injected.

Air conditioning is an extra load on the engine. After starting the air conditioner, engine power is needed to drive the air conditioner compressor. At this time, the engine load increases and the idle speed increases!

Generally speaking, the lower the temperature of the air conditioner in the car, the greater the power required by the compressor and the higher the engine speed! Therefore, it is normal for the engine speed to increase when the air conditioner is turned on.

Extended data:

The idle speed control valve is located on the throttle body, and the throttle valve is almost closed at idle speed. At this time, the idle speed is adjusted by controlling the air volume of the bypass valve. Once the idle valve fails, it will cause unstable idle speed, cold start and air crash.

If the sensor of the air intake or fuel injection system fails, it will lead to various failure phenomena, such as idle jitter, weak acceleration, difficult start and so on. Such as air flow meter, intake pressure sensor, coolant temperature sensor, camshaft position sensor, etc.