1. The temperature is too high

 Three-way catalytic converter does not have catalytic ability at room temperature. The catalyst must be heated to a certain temperature to have the ability of oxidation or reduction. Usually, the ignition temperature of the catalytic converter is 250-350 °C, and the normal working temperature is generally 350-700 °C.

 The catalytic converter will produce a large number of self-high, the higher the oxidation temperature is. When the temperature exceeds 850-1000 °C, the catalyst of the inner coating is likely to fall off and the carrier is broken.

 Therefore, attention must be paid to the control of various factors that cause the increase of exhaust temperature, such as the late ignition time or the disordered ignition order, the fire break, etc., which will make the unburned mixture enter the catalytic reactor, resulting in the excessive exhaust temperature and affecting the efficiency of the catalytic converter.

2. The exhaust is deteriorating

 The catalytic converter has a certain limit on the conversion ability of pollutants, so the original exhaust must be reduced to low through the internal purification technology. If the concentration and total amount of the exhaust pollutants are too large, such as the mixed gas is too thick, it will affect the catalytic conversion ability of the catalyst and reduce its conversion efficiency.

 In addition, because there are a large number of HC and CO in the exhaust gas after entering the catalytic reactor, excessive oxidation reaction will occur in it, and a large amount of heat generated by the oxidation reaction will cause the catalytic reactor to be damaged by excessive temperature.

3. Chronic poisoning The catalyst is very sensitive to elements such as sulfur, lead, phosphorus and zinc. Sulfur and lead come from gasoline, phosphorus and zinc from lubricating oil.

 These four substances and their oxide particles formed after combustion in the engine are easy to be adsorbed on the surface of the catalyst, so that the catalyst can not contact with the exhaust gas, thus losing the catalytic effect, namely the so-called "poisoning" phenomenon.

4. Failure of oxygen sensing path

 In order to achieve good exhaust gas catalytic rate, it is necessary to install oxygen sensors in the engine exhaust pipe and realize closed-loop control. The working principle is that the oxygen sensor will measure the concentration of oxygen in the exhaust gas, convert it into electrical signals and send them to ECU, so that the air-fuel ratio of the engine can be controlled in a small and close to the ideal area.

 If the air-fuel ratio is large, although the conversion rate of CO and HC is slightly increased, the conversion rate of NOx is sharply reduced to 20%, so the best air-fuel ratio must be ensured.

 If the fuel contains lead and silicon, it will cause oxygen sensor poisoning. In addition, improper use will also cause carbon deposition of oxygen sensor, ceramic fragmentation, heater resistor wire burnout, internal circuit breakdown and other faults.

 The failure of oxygen sensors will lead to the failure of air-fuel ratio, the deterioration of exhaust conditions, the reduction of catalytic converter efficiency, and the reduction of catalytic converter service life for a long time.

5. Surface area carbon When the car is working at low temperature for a long time, the three-way catalyst can not start, the soot discharged from the engine will be attached to the surface of the catalyst, causing no contact with CO and HC. In the long run, the pores of the carrier will be blocked, affecting its conversion efficiency.

6. Not matching with the engine

 Even if it is the same engine, the same three-way catalytic converter, different models, the common working range of the engine is different, the exhaust condition changes, and the location of the three-way catalytic converter is different, which will affect the catalytic conversion effect of the three-way catalytic converter.Therefore, different vehicles should use different three-way catalytic converters.