Idle speed is the engine's operating state under no-load conditions. While seemingly simple, it requires precise control. The ECU monitors engine speed, throttle position, and the operating status of auxiliary equipment such as the air conditioner and alternator, automatically adjusting the throttle opening and fuel injection to maintain a stable idle speed.
When the air conditioner is turned on, the engine load increases. The ECU automatically increases the throttle opening and raises the engine speed to ensure the engine has sufficient power to drive the air conditioner compressor, while maintaining a stable idle speed and preventing the engine from stalling due to excessive load.