What Are the Reasons for Excessive Vehicle Exhaust Emissions?
2 Answers
Reasons for excessive vehicle exhaust emissions: 1. Abnormal engine operation: The engine may experience issues such as misfiring, spark plug oil leakage, or oil mixing. When accelerating, the engine runs unevenly and lacks power. 2. Dirty vehicle systems: This usually occurs in relatively new vehicles, but the test results show excessive emissions, or the excess is minor (only a few percent or fractions of a percent). This indicates that the vehicle's exhaust treatment system (including the catalytic converter and oxygen sensor) is not significantly faulty. The cause of excessive emissions may be due to the three major systems (intake system, exhaust system, and fuel system) being too dirty. 3. Catalytic converter failure: A faulty catalytic converter is the primary reason for excessive vehicle exhaust emissions. The catalytic converter is the most important external purification device installed in the vehicle's exhaust system. It converts harmful gases such as CO, HC, and NOx from vehicle exhaust into harmless carbon dioxide, water, and nitrogen through oxidation and reduction. 4. Oxygen sensor damage: In engines using catalytic converters to reduce exhaust pollution, the oxygen sensor is an essential component. It detects the oxygen concentration in the exhaust and sends feedback signals to the ECU, which controls the fuel injector to adjust the fuel injection volume. This keeps the air-fuel ratio of the mixture near the theoretical value, ensuring more complete fuel combustion. 5. Vehicle aging: If the vehicle has traveled over 450,000 kilometers or is more than 15 years old, various components may show significant aging, poor contact, inadequate sealing, or insufficient pressure.
I previously failed my vehicle inspection due to excessive tailpipe emissions. The mechanic said there are quite a few common causes, such as poor fuel quality with too many impurities, which increases pollutants when combustion is incomplete; a deteriorated or failed catalytic converter that can't effectively convert harmful gases; a clogged air filter preventing proper airflow, leading to a lean air-fuel mixture and reduced combustion efficiency; or a faulty O2 sensor causing inaccurate readings and improper fuel injection by the engine. During cold starts, low temperatures mean the engine isn't warmed up, resulting in incomplete combustion. Prolonged idling also leads to excessive carbon buildup. I recommend regular maintenance, checking filters and small components, fueling up at reputable gas stations, and avoiding overloading to reduce strain. In short, don't ignore minor issues—address excessive emissions promptly to avoid failing the annual inspection and damaging your car.
