Automobile annual inspection exhaust gas exceeds the standard. What's the problem?

Where is the problem of excessive exhaust gas in automobile annual inspection?

After the implementation of the national six emission standards, it means that the detection of automobile exhaust is becoming more and more strict. Many cars can't be tested, so they have to stay at home. If they can't get on, they will basically be scrapped. But many of these cars are in good condition. Today we will talk about the topic of automobile exhaust detection.

Excessive detection of automobile exhaust gas is mostly related to oxygen sensor or three-way catalytic converter. The oxygen content in exhaust gas is detected by oxygen sensor, and the signal data is transmitted back to ECU, and the fuel injection quantity is calculated according to the returned signal, so as to ensure that the air-fuel ratio is always maintained near the theoretical value. The oxygen sensor can correct the air-fuel ratio. When the air-fuel ratio is controlled at 14: 7, the purification efficiency of the three-way catalyst is also the highest. Too rich or too thin mixer will lead to the change of air-fuel ratio, and will also affect the fuel consumption and power of the engine. At present, most vehicles are equipped with two oxygen sensor three-way catalysts, one in front and one in the back. The front is used to test whether the engine empty pen is qualified, and the back is used to test the purification effect of the three-way catalyst. That is what we often say, oil before gas.

If the car runs for a long time, the oxygen sensor is poisoned, too much carbon is deposited, and the heating wire is broken, which will lead to the abnormal operation of the oxygen sensor. The cause of poisoning is that the lead content in gasoline is too high and carbon deposit is too high, which leads to abnormal signal of oxygen sensor. Broken heating wire will lead to heating failure. Because the working temperature of oxygen sensor is above 300 degrees Celsius, the initial temperature is usually completed by electric heating wire. Once the monitoring data of oxygen sensor is abnormal due to these reasons, there will be too little fuel injection, insufficient vehicle power, frequent engine shutdown, or too high fuel injection, resulting in increased fuel consumption and substandard exhaust emissions.

Three-way catalytic converter is the most important off-site purification device installed in automobile exhaust system. It can make the harmful gases such as carbon monoxide, nitrogen hydride and nitrogen oxide discharged from automobile exhaust undergo redox reaction through the purifying agent in the three-way catalytic converter, so that the automobile exhaust can be converted into harmless carbon dioxide, water and nitrogen to purify the automobile exhaust. When the car is driving for a long time, the three-way catalytic converter may fail, block and break the carrier, resulting in poor purification effect and natural exhaust gas exceeding the standard.

After talking about why the exhaust gas will exceed the standard, let's talk about what to do when the test is unqualified. The first is to go to a regular gas station to refuel. The sulfur content of unqualified fuel usually exceeds the standard, which will make the three-way catalyst unable to completely purify the exhaust gas, and will also lead to the blockage of the three-way catalyst, the failure of the oxygen sensor and the increase of carbon deposition. The second is to check the three-way catalytic converter. If it is blocked, it can be cleaned. If it is broken, it must be replaced. Third, check the oxygen sensor and clean it together with the three-way catalyst if necessary. The fourth is to do some preparatory work before the on-line inspection work, such as maintaining the engine in advance, preheating the car in advance before going online, and so on. The fifth is to find scalpers. As long as you are willing to spend money, there will always be someone to help you settle all this. The above are the reasons for the unqualified annual inspection of automobile exhaust and some common treatment methods.