What are the reasons for a car's exhaust emissions failing to meet standards?
2 Answers
There are four main reasons why a car's exhaust emissions may fail to meet standards: 1. Aging of car components: During long-term use, many parts of a car may age, leading to a noticeable decline in performance. For vehicles used over an extended period, it can be difficult to meet emission standards, possibly due to the level of production technology causing excessive emissions. 2. Poor fuel quality: When refueling, if the fuel quality is not guaranteed, the high impurity content in low-quality fuel can easily lead to excessive emissions. This may result in the car failing the annual inspection, especially for imported cars, which have stricter fuel requirements. 3. Catalytic converter failure: After prolonged use, the catalytic converter may malfunction due to carbon buildup in the car. Therefore, regular maintenance should include checking the catalytic converter to avoid emission-related failures during the annual inspection. 4. Design or production defects causing the vehicle to exceed standard atmospheric pollutant emissions.
Last time my annual inspection showed excessive exhaust emissions. The mechanic said it was due to a clogged catalytic converter—it's like a mask for the exhaust; when clogged, nothing gets filtered properly. It could also be a faulty oxygen sensor, which monitors oxygen levels in the exhaust. If it fails, the car starts injecting fuel haphazardly. Insufficient engine cylinder pressure or burning oil (blue smoke) can also cause excessive emissions, especially in older cars where piston ring wear leads to oil leakage. Bad spark plugs result in incomplete combustion, making black smoke from the exhaust particularly noticeable. The most troublesome issue is abnormal ECU data in the engine control unit, which messes up the air-fuel mixture ratio—this requires a computer diagnostic to detect.
