What is the reason for the car idling?

There are many reasons for the unstable idle speed of automobiles, such as air leakage in the intake system, low fuel pressure, air filter blockage, atomized oil leakage from the fuel injector, improper idle speed adjustment, poor spark plug operation, air flowmeter failure and so on. So many can't be introduced one by one, so I chose a few common ones to analyze.

1. The normal idle speed of EFI engine is determined by the idle speed control valve. According to the engine speed, temperature, throttle switch, air conditioning switch and other signals, after calculation, the electronic control unit opens the air intake bypass channel leading to the idle speed control valve or directly increases the throttle opening, thus increasing the air intake and improving the engine idle speed. If there is oil pollution and carbon deposition, the idle speed control valve will jam or the throttle valve will not close normally, which will make the electronic control unit unable to adjust the engine idle speed accurately.

2. In general, the air intake must be strictly limited. If the air intake pipe leaks, the air flow sensor can't measure the real air intake, and the electronic control unit can't accurately control the air intake, which leads to the unstable idle speed of the car.

3. The fuel injector leaks or is blocked, or the circuit fault affects the fuel injection quantity and quality, which leads to the inability to inject fuel according to the instruction of the electronic control unit, thus causing the mixture to be too rich or too thin, resulting in poor operation of individual cylinders and unstable idle speed.

4. Air flowmeter is one of the main bases for ECU to infer fuel injection quantity. The fault of the air flow meter and its circuit makes the electronic control unit unable to receive the air flow signal or the received signal is distorted, which leads to inaccurate fuel injection by the injector, too rich or too thin mixture, resulting in too low rotation speed and fire.

5. When the engine is idling, the automobile electronic control unit will interpret the thermal state of the engine according to the signal input by the coolant temperature sensor, that is, the water temperature sensor, and correct the fuel injection quantity. If the water temperature sensor is not good, the output signal will be inaccurate, resulting in low idle speed, misfire and soft operation.

Of course, in addition to the above situation, there are other factors that may lead to the idling flameout of the car, so we should check them one by one to solve the idling failure of the car.