What are the causes of high idle speed in motor vehicles?
1 Answers
There are many reasons that can cause high idle speed in vehicles, which are detailed as follows: Idle speed control valve malfunction: The normal idle speed of an electronic fuel injection engine is determined by the idle speed control valve. The electronic control unit (ECU) calculates signals from engine speed, temperature, throttle position, and air conditioning switch, then adjusts the idle speed control valve to open the intake bypass channel or directly increase the throttle opening, thereby increasing the air intake to raise the engine idle speed. If oil contamination or carbon deposits cause the idle speed control valve to stick or the throttle to fail to close properly, the ECU will be unable to accurately regulate the engine's idle speed. Intake system air leakage: Under normal circumstances, the air intake must be strictly controlled. If there is a leak in the intake pipe, the air flow sensor cannot measure the actual air intake, leading to inaccurate air intake control by the ECU and resulting in unstable vehicle idle speed. Fuel injector dripping or clogging: If the fuel injector drips or becomes clogged, it cannot spray fuel according to the ECU's instructions, causing the air-fuel mixture to become too rich or too lean. This leads to poor performance in individual cylinders and unstable idle speed.
