What Causes Foul Smell in Small Car Exhaust?
2 Answers
Small car exhaust smell can occur during hot idling or at high RPM, sometimes accompanied by weak acceleration, indicating severely excessive exhaust emissions, primarily CO over the limit. Automotive Exhaust: Automotive exhaust is a byproduct of engine combustion. After purification by the catalytic converter, normal exhaust mainly contains water vapor, nitrogen, carbon dioxide, and small amounts of nitrogen oxides. For vehicles in normal working condition, the exhaust is colorless and odorless. If the exhaust emits an unusual smell, such as a foul odor, immediate vehicle inspection and repair are necessary. Reasons for CO Overlimit: The main reason for CO overlimit is an overly rich air-fuel mixture. Excessive fuel or insufficient air intake leads to incomplete combustion of carbon in the fuel, producing CO. Normal combustion should produce CO2, which is a colorless and odorless gas. Exhaust containing excessive CO can cause oxygen sensor failure, high-temperature sintering of the catalytic converter, and even damage to the vehicle's computer. Therefore, if a vehicle's exhaust emits a foul smell, it is best to address the issue immediately to avoid greater losses.
When I smell a foul odor from my car's exhaust while driving, it's usually due to incomplete combustion in the engine, such as aging spark plugs or clogged fuel injectors, which prevent the fuel from burning completely and release strange smells. Another common issue is a damaged catalytic converter, which is responsible for purifying exhaust gases. Once it fails, harmful gases are directly emitted, smelling like sulfur or rotten eggs. There could also be excessive carbon deposits accumulating in the pistons and cylinders, affecting normal operation, or a clogged air filter causing insufficient air intake and making the fuel mixture too rich. If you've just filled up with cheap gasoline, poor fuel quality can also cause this. If not repaired promptly, it not only affects driving safety but may also damage the engine's lifespan. I always recommend going to a repair shop for an exhaust test and replacing any worn-out parts as soon as possible.
