What Are the Main Reasons for Excessive Vehicle Exhaust Emissions?

[QuinnLynn]

There are several reasons for excessive vehicle exhaust emissions: 1. Vehicle aging: If a vehicle has traveled more than 450,000 kilometers or has been in use for over 15 years, its components will show significant aging, poor contact, poor sealing, and insufficient pressure. 2. Failure of the three-way catalytic converter: The failure of the three-way catalytic converter is the primary reason for excessive vehicle exhaust emissions. The three-way 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 emitted by the vehicle's exhaust into harmless carbon dioxide, water, and nitrogen through oxidation and reduction reactions. When high-temperature exhaust gases pass through the purification device, the catalyst in the three-way catalytic converter enhances the activity of CO, HC, and NOx, promoting certain oxidation-reduction chemical reactions. CO oxidizes at high temperatures into colorless, non-toxic CO2 gas; HC compounds oxidize into water (H2O) and CO2; and NOx reduces into nitrogen and oxygen. These three harmful gases are transformed into harmless gases, thereby purifying the vehicle's exhaust. 3. Abnormal engine operation: The engine may experience issues such as misfiring, spark plug oil leakage, or oil mixing, causing it to run unevenly and weakly when the throttle is increased. 4. Dirty vehicle systems (intake system, exhaust system, fuel system): This situation usually occurs in relatively new vehicles, but the test results show excessive emissions or only slight exceedances by a few percent or fractions of a percent. This indicates that the vehicle's exhaust treatment system, including the three-way 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, fuel system) being excessively dirty.

[VonClara]

As a seasoned mechanic with years of experience, the most common issue I see with excessive car emissions is inadequate engine maintenance. Worn-out spark plugs or ignition system failures lead to incomplete fuel combustion, producing large amounts of CO and HC. A dirty air filter blocking the intake disrupts the air-fuel ratio, also increasing emissions. Additionally, a failed catalytic converter means exhaust gases aren’t purified. Older cars are more prone to this, such as oxidized wiring or excessive carbon buildup in the fuel system, leading to reduced power. Frequent hard acceleration while driving puts a heavy load on the engine, worsening combustion efficiency. I advise car owners to regularly check spark plugs and air filters, replace worn parts, and not skimp on small expenses. If emissions are severely excessive, promptly visit a professional shop for tuning—replacing the catalytic converter can solve most of the problem.

[JasmineFitz]

Having driven for decades, I believe there are various reasons for excessive exhaust emissions, but the core issues are improper use and neglect of maintenance. Older car engines are outdated, designed with lower emission standards, making them naturally prone to exceeding limits. Additionally, poor fuel quality, such as using substandard gasoline, leads to carbon buildup or incomplete combustion. Air-fuel ratio imbalance is also common, caused by inaccurate ignition timing or damaged sensors that fail to control fuel injection properly. If owners neglect regular oil changes or filter replacements, accumulated dirt can significantly reduce engine efficiency. Excessive idling also contributes to the problem, wasting fuel. I always advise my friends to perform regular maintenance and not wait until the inspection fails to regret it. Choosing reputable gas stations and timely checks can prevent many issues.

[StIsaac]

As a new car owner, I've found that excessive exhaust emissions are closely linked to daily driving habits. The main causes include a faulty oxygen sensor providing inaccurate signals that prevent proper air-fuel mixture adjustment, leading to dramatically increased emissions. Frequent hard braking or aggressive acceleration during driving results in incomplete combustion and increased carbon buildup. Neglecting regular maintenance, such as failing to replace the three filters, allows dirty air intake that reduces combustion efficiency. Older vehicle models with outdated emission systems also contribute - upgrading catalytic converters or components can help. When I encountered emission issues, I promptly visited the 4S shop where simple diagnostics identified the root cause and prevented fines.

[MariaLynn]

From an environmental perspective, excessive vehicle emissions primarily stem from technical flaws and human factors. Outdated engine designs lead to incomplete fuel combustion, resulting in excessive hydrocarbon emissions. The failure of three-way catalytic converters is critical, as they cannot transform pollutants; malfunctioning oxygen sensors disrupt the air-fuel ratio balance. Prolonged idling in urban traffic congestion exacerbates fuel wastage and emissions. Driving habits such as rapid acceleration or overloading increase engine strain. I recommend adopting eco-driving techniques, such as smooth acceleration and regular inspections, which save money and reduce pollution, benefiting society in the long run.