What to Do When the Engine Idle Speed is Unstable and Fluctuates?

[Asher]

Here are the specific methods to deal with unstable idle speed that fluctuates and lacks acceleration power: 1. The correct idle speed of an electronic fuel injection engine is ensured by the electronic idle speed control valve. The ECU adjusts the idle speed control valve based on signals such as engine speed, temperature, throttle switch, and air conditioning. 2. When the idle speed is lower than the set value, the computer commands the idle speed control valve to open the intake bypass channel or directly increase the throttle opening to increase the intake air volume, thereby raising the engine idle speed. 3. When the idle speed is higher than the set value, the computer commands the idle speed control valve to close the intake bypass channel, reducing the intake air volume and lowering the engine speed. Due to oil contamination, carbon deposits causing sluggish or stuck movement of the idle speed control valve, or the throttle not closing properly, the ECU cannot correctly adjust the engine idle speed, leading to unstable idle speed. 4. Diagnostic method: Check the operation sound of the idle speed control valve. If there is no sound, the idle speed control valve is faulty. Troubleshooting involves cleaning or replacing the idle speed control valve and using a dedicated decoder to perform a basic setting of the idle speed.

[CaliLee]

I've been driving for over 20 years and have encountered unstable idle speed issues many times. The most common causes are throttle valve carbon buildup causing sticking, or clogged air filters restricting airflow. DIY solutions are quite simple: First, turn off the engine and open the hood, locate the throttle valve (usually connected to the intake pipe), spray some specialized cleaner and wipe to remove carbon deposits. Also check if the air filter is dirty - replacing it can improve performance. Worn spark plugs are another frequent culprit - remove and inspect the electrodes for erosion or carbon buildup, replacing a new set only costs a few dozen yuan. Additionally, listen to the engine sound - if there's a hissing noise, it might indicate vacuum hose leakage which can be fixed by tightening. Don't ignore these minor issues as unstable idle speed will dramatically increase fuel consumption and affect driving experience. Regular throttle valve cleaning every 10,000 km is the best prevention.