What is the reason for Jetta's high idle speed?

Jetta's high idle speed is due to the failure of idle speed control valve, air leakage in air intake system, dripping or blockage of fuel nozzle. The following explains the above reasons in detail: Idle speed control valve failure: The normal idle speed of EFI engine is determined by idle speed control valve. According to the engine speed, temperature, throttle switch idle speed adjustment and other signals, after calculation, the electronic control unit will open the intake bypass channel of the idle speed control valve or directly increase the throttle opening, thus increasing the intake air volume and improving the engine idle speed. If there is oil pollution and carbon deposition, the idle speed control valve will act, and the throttle valve will not be closed normally, resulting in the ECU not being able to accurately adjust the engine idle speed. Air leakage in air intake system: In general, air intake must be strictly restricted. If the air intake pipe leaks and the air flow sensor can't measure the actual air intake, then the electronic control unit can't accurately control the air intake, resulting in unstable idle speed of the car. Dropping or blocking of oil nozzle: The oil nozzle leaks or is blocked, which makes it impossible to inject fuel according to the instruction of the electronic control unit, and the mixture is too rich or too thin, which leads to poor operation of individual cylinders and unstable idle speed.