Why is there abnormal noise when starting the car?

[StCaroline]

Reasons and solutions for abnormal noise when starting the car are as follows: 1. The engine temperature is too low. During cold starts, the engine temperature is too low for normal operation. Solution: This is a normal phenomenon; simply wait for the engine temperature to rise to normal levels. 2. Thermal expansion of the car's three-way catalytic converter. Abnormal noise that occurs when the car is first started but disappears after a while is caused by the thermal expansion of the three-way catalytic converter. Solution: This is a normal phenomenon. 3. Transmission failure. A malfunction in the transmission can cause internal gears to rub, resulting in abnormal noise. Solution: Professional inspection and repair at a repair shop or 4S store are required. 4. Wear of the engine belt or chain. Wear of the engine belt or chain can also cause friction or abnormal noise due to idling when starting the vehicle. Solution: Directly replace the engine belt or chain.