What Causes the 'Bang' Sound When Starting the Engine?
2 Answers
Cold start 'bang' sound may be normal for new cars. Here is some relevant information about gasoline engines: 1. Introduction: A gasoline engine is an engine that uses gasoline as fuel to convert internal energy into kinetic energy. Due to gasoline's low viscosity and fast evaporation characteristics, a fuel injection system can spray gasoline into the cylinder. After compression reaches certain temperature and pressure levels, a spark plug ignites the mixture, causing gas expansion to perform work. 2. Characteristics: Gasoline engines feature high rotational speed, simple structure, light weight, low cost, smooth operation, and convenient maintenance. They are widely used in automobiles, especially in small cars.
I've been repairing cars for nearly 20 years, and that 'bang' sound during startup is mostly caused by backfiring in the exhaust pipe. The main reason is incorrect air-fuel mixture concentration, where unburned fuel enters the exhaust pipe and ignites. There are three common scenarios: first, aging spark plugs with insufficient ignition energy lead to uneven air-fuel mixture during cold starts; second, leaking fuel injectors that continue dripping after engine shutdown cause an overly rich mixture; third, excessive carbon buildup affecting air intake efficiency. When encountering this issue, first check the spark plug electrode gap and carbon deposits, using a borescope to inspect cylinder interiors if necessary. Air-fuel mixture problems can also damage the catalytic converter, so it's best to address them promptly.
