1. The temperature is too high

Three-way catalytic converter does not have catalytic ability at normal 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. When the catalytic converter works, a large number of catalysts are produced. The higher the amount, the higher the temperature of oxidation. When the temperature exceeds 850-1000 °C, the catalyst in 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 high exhaust temperature, affecting the efficiency of the catalytic converter.

2. Chronic poisoning

The catalyst is very sensitive to sulfur, lead, phosphorus, zinc and other elements. Sulfur and lead come from gasoline, phosphorus and zinc come 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.

3. Surface area carbon

When the car works in a low temperature state for a long time, the three-way catalyst can not start, the soot emitted by 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.

4. Exhaust deterioration

The catalytic converter has a certain limit on the conversion ability of pollutants, so it must be minimized by internal purification technology.If the concentration and total amount of the components 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 high temperature.

5. Not matching with the engine

Even if it is the same engine and the same three-way catalytic converter, 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.

6. Failure of oxygen sensing path

In order to achieve the best 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 oxygen concentration 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%. Therefore, the key to achieve the best air-fuel ratio is to ensure the normal operation of oxygen sensors. If the fuel contains lead and silicon, it will cause oxygen sensor poisoning. In addition, improper use will also cause oxygen sensor carbon deposit, ceramic fragmentation, heater resistor wire burnout, internal circuit breakdown and other failures. The failure of oxygen sensors will lead to the improper 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.