What is the reason why the 3008 emission standard is unqualified?

A sensor failures such as air flow meter, throttle position sensor and water temperature sensor do not occur frequently, mainly due to various reasons of signal or line failures. However, the symptoms of sensor failures that can cause insufficient combustion of mixed gas are very easy to judge, because in addition to excessive exhaust emissions, engine idling instability and jitter are almost * * *.

Second, the front oxygen sensor other sensors will not be troubled by carbon deposition, while the oxygen sensor is different. The probability of problems with the front oxygen sensor is no less than that of the three-way catalyst. Insufficient combustion of engine mixture will always produce a lot of carbon deposits, some of which are attached to the inside of the three-way catalyst and some to the outside of the oxygen sensor. As time goes by, if carbon deposition is serious, the sensitivity of oxygen sensor will decrease. The failure of the front oxygen sensor will cause the ECU not to correctly sense the oxygen concentration in the exhaust gas and accurately control the fuel injection quantity, resulting in insufficient combustion of the mixed gas and excessive emissions. For convenience, the front oxygen sensor is generally cleaned together with the three-way catalyst, and can be soaked in oxalic acid solution (concentration: 10%) for cleaning.

Third, the engine carbon deposit problem spark plug carbon deposit, nozzle carbon deposit, intake carbon deposit, etc. If there is more carbon deposit, the quantitative change will produce qualitative change, which will affect the engine working condition to a certain extent and will also cause insufficient combustion of mixed gas. Insufficient combustion of mixed gas not only produces a lot of carbon deposits, but also easily leads to excessive exhaust pollution. Therefore, if the automobile exhaust gas is unqualified in the annual inspection, and the three-way catalyst and oxygen sensor are still being cleaned, you can consider doing a deep cleaning of carbon deposit on the engine.

Fourth, the blockage of the filter screen causes poor oil flow. The blockage of oil passage is mostly caused by impurities in fuel. Although it is different from carbon deposition, it will also affect the air-fuel ratio of the engine, resulting in insufficient combustion of the mixture and the same emission of pollution. The common problems of oil circuit blockage are fuel pump filter screen blockage, fuel filter blockage for a long time, and unintentional addition of some inferior fuel, which leads to oil circuit blockage.