What Causes the Roaring Sound When Starting a Car?
4 Answers
Introduction to the main reasons for loud roaring sounds when starting a car: 1. Cold start noise: This "clicking" noise occurs because the oil pump hasn't fully built up oil pressure during a cold start, leading to insufficient lubrication of components. Normally, the clicking noise will disappear after the engine runs for a while. 2. Charcoal canister solenoid valve operation noise: The charcoal canister solenoid valve opens the electromagnetic valve between the charcoal canister and the intake manifold after the engine starts, allowing adsorbed gasoline vapors and air to enter the cylinders for combustion. This not only reduces emissions but also lowers fuel consumption. This component can also produce a clicking sound during operation. 3. Engine mount aging or loosening: Engine mounts are rubber blocks placed between the engine and the frame. Their purpose is to reduce vibration and cushion the engine's operation while securing the engine in place. If these mounts age or loosen, the engine may shake, and in severe cases, a "clicking" noise may occur. This can be resolved by replacing the engine mounts. 4. Overly rich air-fuel mixture: When the engine's air-fuel mixture is too rich, symptoms include difficulty accelerating after starting, uneven engine operation, black smoke from the exhaust pipe, a clicking noise from the engine, sometimes backfiring, reduced engine power, and increased fuel consumption. This is often related to carbon buildup or clogged filters and usually doesn't require major repairs.
I've been repairing cars for over a decade, and that loud roar during cold starts is most likely the engine's self-check function in action. When temperatures are low, the vehicle's computer automatically increases fuel injection to raise the RPM, specifically to help the oil pump quickly build oil pressure while also preheating the catalytic converter. This sound is particularly noticeable in winter, resembling a sports car's roar, but it's normal as long as the RPM drops back to 800 within ten seconds. However, if you hear metallic grinding noises, be cautious—it could indicate a worn-out alternator belt or issues with the timing chain tensioner. Older German cars often exhibit this, while newer models tend to show it less.
Just installed an engine sound simulator on my newly acquired electric car last week, so I've been researching the principles of engine roar. During startup, the high-revving sound mainly relies on the ECU fully opening the intake valves while the dual injection system enriches the fuel-air mixture. It's somewhat similar to stomping on the accelerator before the tachometer responds - the key indicator is whether white exhaust smoke appears after the roar, which could signal incomplete combustion due to aging ignition coils. Regular throttle body cleaning can reduce this phenomenon, especially for turbocharged city commuters.
I remember being really scared the first time I encountered this situation, thinking my car that I had just bought half a year ago was about to explode. The technician said that the fuel pump produces cavitation noise when building pressure, especially when the fuel filter is clogged, it gets even louder. Now I've learned my lesson: when parking on a slope, starting with the front of the car facing downhill reduces the roaring sound significantly. During the last maintenance, I found that cracked engine mounts can also amplify the vibration noise, and these rubber parts should be replaced every five years. Don't believe the online advice about pulling out fuses to solve the issue, as it might damage the car's computer if not done properly.
