What is the normal idle speed when starting a car engine?

[HadleyFitz]

When starting a car engine, an idle speed of 700 to 800 revolutions per minute (RPM) is considered normal. The impacts of engine idling include: 1. Increased carbon buildup in the engine; 2. Shortened engine lifespan; 3. Overly rich air-fuel mixture in the engine, which can easily damage the three-way catalytic converter; 4. Loosening of the vehicle's braking system, potentially leading to accidents; 5. Increased exhaust emissions from the engine cylinders. Car idling refers to the engine running without any load, only overcoming internal frictional resistance, without delivering power output externally, maintaining the minimum stable operating speed of the engine. The idle speed can be adjusted by modifying the throttle opening size and the idle fuel supply quantity.