What causes abnormal noise when the engine is just started?

[StVivienne]

The reason for abnormal noise when the engine is just started (cold start) is usually due to the loss of lubrication inside the starter motor's gears, causing stiffness and sticking, which affects the timely return of the gears. That is, when starting the engine, the starter motor rotates to drive the flywheel, thereby starting the engine. At this time, the engine's speed is driven by the starter motor, so the engine speed is lower than the starter motor's speed. When the engine starts and its speed exceeds the starter motor's speed, the ignition switch is manually turned off, and the starter motor shuts down. Information about cold starts is as follows: 1. A cold start refers to starting the engine when the coolant temperature is low, usually after the car has not been started for a long time (such as after overnight parking). 2. An engine cold start means that the engine has been shut down for a period of time, and it starts when its internal temperature matches the ambient temperature.