What are the reasons for high engine idle speed?

[ElenaAnn]

Reasons for high engine idle speed: 1. A dirty throttle valve can cause errors in the throttle opening, reduce its sensitivity, and prevent it from closing properly during idle, leading to abnormal idle speed; 2. A faulty idle valve can prevent the correct adjustment of idle speed, causing issues such as unstable idle, difficulty in cold starts, and in severe cases, no idle at all—the engine may stall as soon as the accelerator is released; 3. Sensor malfunctions can lead to incorrect computer judgments or computer failures, resulting in abnormal engine idle speed; 4. Fuel injector leakage or blockage can prevent them from spraying fuel according to the ECU's instructions, causing the air-fuel mixture to be too rich or too lean, leading to poor performance in individual cylinders and unstable engine idle speed.