What are the reasons for excessive vehicle exhaust emissions?
4 Answers
The reasons for excessive vehicle exhaust emissions are: 1. Engine misfiring; 2. Spark plug oil leakage; 3. Failure of the three-way catalytic converter; 4. Dirty intake system, exhaust system, or fuel system; 5. Faulty oxygen sensor; 6. Aging components, poor contact, or poor sealing; 7. Incomplete fuel combustion. The solutions for excessive vehicle exhaust emissions are: 1. Replace the engine; 2. Replace the spark plugs; 3. Replace the three-way catalytic converter; 4. Check the oxygen sensor; 5. Clean the intake system, exhaust system, and fuel system; 6. Add additives to the engine oil. Vehicle exhaust is an environmental pollution caused by the waste gases emitted by vehicles, and its pollutants include: carbon monoxide, hydrocarbons, nitrogen oxides, sulfur dioxide, lead compounds, and particulate matter.
I previously encountered older vehicles with excessive exhaust emissions, and found that many issues stem from the ignition system. Worn spark plugs and leaking high-voltage wires are the most common problems, as untimely ignition prevents complete fuel combustion. Another issue is incorrect air-fuel mixture ratios, caused by dirty mass airflow sensors or failed oxygen sensors, which can mislead the engine control unit into injecting too much fuel. Vehicles frequently used for short trips are prone to carbon buildup clogging the catalytic converter—when this gets blocked, harmful gases are directly emitted. Additionally, minor issues like a stuck crankcase ventilation valve or oil leaks in the turbocharger can lead to bigger problems. I recommend regularly reading fault codes and performing exhaust gas analysis, and paying extra attention to ignition components and sensor conditions for vehicles over 80,000 kilometers.
I've observed that fuel quality and driving habits are crucial. Using lower-grade gasoline with high sulfur content can lead to excessive carbon buildup, clogging the catalytic converter and causing emissions to skyrocket. Frequent rapid acceleration or heavy throttle usage is particularly fuel-intensive, as unburned gasoline turns into large amounts of hydrocarbons in the exhaust. Neglecting air filter maintenance is another issue – restricted airflow forces the ECU to increase fuel injection, creating a rich mixture that produces carbon monoxide. This problem worsens when warming up the engine for over three minutes in winter, especially in older carburetor-equipped vehicles. I recommend developing smooth driving habits and checking the exhaust system's sealing during regular maintenance.
My car failed the last emission test due to neglected maintenance. The catalytic converter I replaced three years ago had actually failed long ago, but I kept putting off replacing it to save money, resulting in its purification efficiency dropping below 40%. Recent long-term short-distance commuting caused severe engine carbon buildup, almost clogging the spark plug gaps - no wonder it was emitting black smoke. The air filter hadn't been changed for two years, with the intake vent caked in oil sludge. Worst of all, the mechanic misconnected the vacuum tube during the last repair, causing complete EGR system failure. I advise everyone not to follow my example of delaying maintenance, especially for vehicles over five years old - pay special attention to exhaust-related components.
