Why does the engine speed fluctuate?

[Kingston]

The cause of fluctuating engine speed is that the ECU receives an acceleration signal during idle conditions, while the engine is actually operating at idle with less air intake, resulting in an overly rich air-fuel mixture and a rise in speed. When the ECU receives an "overly rich mixture" signal from the O2 sensor, it reduces fuel injection, causing the mixture to become too lean and the speed to drop. Here are the related details: 1. Engine speed: The engine speed determines the number of power cycles per unit time or the effective power output of the engine, meaning the effective power varies with different speeds. 2. Introduction to engines: An engine (Engine) is a machine that converts other forms of energy into mechanical energy, including internal combustion engines (reciprocating piston engines), external combustion engines (Stirling engines, steam engines, etc.), jet engines, electric motors, etc.