Why is the idle speed high in winter?
2 Answers
In winter, the high idle speed occurs because the engine's normal operating water temperature is around 90 degrees Celsius. In extremely low temperatures, after the engine starts, the water temperature sensor sends a signal to the ECU, prompting the engine to increase fuel injection and air intake, thereby raising the engine speed to quickly reach the normal operating temperature. As the engine temperature gradually rises, the idle speed will also gradually decrease to normal levels. The increase in idle speed after a cold start is a normal phenomenon, serving as a protective measure for the engine by the car, and also aimed at improving combustion efficiency and meeting emission standards. The car engine is the device that provides power to the vehicle, acting as the heart of the car, and determines the vehicle's power, fuel economy, stability, and environmental friendliness.
I'm all too familiar with the high RPM during cold starts in winter. It's mainly because the engine control unit (ECU) helps the engine warm up quickly, as engine oil becomes as thick as syrup in low temperatures, increasing cylinder friction resistance. To maintain stable operation, the ECU automatically injects more fuel to raise the RPM, usually around 1500 RPM is normal. The key is to see if it drops to around 800 RPM after the coolant temperature rises. If it doesn't come down after ten minutes, it needs checking. I've personally experienced situations where the oxygen sensor was frozen, and another time when carbon buildup on the throttle body jammed the intake flap. Remember not to stomp on the gas pedal when warming up the car—wait until the blue coolant temperature light goes off before driving, or it can seriously damage the catalytic converter.
