What are the causes of excessive nitrogen oxides in exhaust emissions?
2 Answers
Automobile exhaust nitrogen oxides exceed the standard mainly due to poor intake system, engine carbon deposits, cylinder wear, failure of the three-way catalytic converter, oxygen sensor out of control, etc. Different treatment methods should be adopted according to the causes of exceeding the standard: 1. Check the engine: A simple check can be done. The engine is the heart of the car. To check whether the engine is normal, you can remove the spark plug to see if there is any engine oil. If it is very clean, it means the ignition is normal, and the engine does not have oil leakage. Observe when accelerating the throttle to see if the operation is smooth and powerful. If the above checks are no problem, it is normal. 2. The three major systems of the vehicle are too dirty: This situation generally occurs when the vehicle is still relatively new, but the test results exceed the standard, or the excess is not serious, only a few percent or a few tenths of a percent. This situation indicates that the vehicle's exhaust treatment system, namely the three-way catalytic converter and oxygen sensor, does not have major problems. The main reason for the excessive exhaust emissions is that the three major systems of the vehicle (intake system, exhaust system, fuel system) are too dirty.
Having driven for decades, excessive nitrogen oxide emissions typically occur when the engine is not burning fuel efficiently, such as during hard acceleration or high-speed uphill driving when the engine temperature soars, making it prone to nitrogen oxide formation. Another common cause is issues with the exhaust gas recirculation (EGR) system. If the valve is clogged or worn out, exhaust gases fail to recirculate to cool the air-fuel mixture, leading to a spike in nitrogen oxide emissions. Additionally, if the three-way catalytic converter fails, it can't convert harmful gases, allowing pollutants to be released directly. Poor fuel quality and a dirty air filter also contribute negatively. I recommend regular exhaust emission checks. If levels exceed standards, promptly replace parts or seek professional repairs to avoid health impacts and annual inspection failures.
