What Causes the Brief Rattle Sound When Starting a Car?

[KeeganLee]

The causes of the rattle sound during car startup are as follows: 1. Cold Start Noise: Many car owners hear a "rattle" noise from the engine compartment during a cold start. This noise occurs because the oil pump hasn't fully built up oil pressure yet, leading to insufficient lubrication of engine components. Normally, the rattle sound disappears after the engine runs for a while. 2. Charcoal Canister Solenoid Valve Operation Noise: The charcoal canister solenoid valve opens after engine startup, allowing gasoline vapors stored in the charcoal canister to enter the intake manifold along with air for combustion. This not only reduces emissions but also improves fuel efficiency. This component can also produce a rattle sound during operation.