Oxygen sensor fault reason: Engine black smoke and fuel consumption reasons are the following. (1) the air-fuel ratio of the engine mixture is too strong. Second, due to the poor working of a certain cylinder, the power loss will be greater and the cost of oil will be reduced. (3) some sensors on the vehicle are damaged, resulting in too much PCM control fuel injection. (4) the atomization of the injector is poor or sometimes the oil is leaking. The oil pressure is too high, resulting in excessive oil supply. Troubleshooting: first, use TECH2 to check, no fault code output. Reading the data flow view, it is found that the heating change is normal, but its value is high: the temperature sensor of the coolant is observed, the value of the sensor is about 98 9C, and the temperature of the sensor is normal, and the temperature of the sensor decreases with the starting of the electronic fan, and the other sensors have not been found after scanning and observed. (2) check the spark plugs of each cylinder and find that there is a lot of coke deposition. It is estimated that the mixture is too thick for a long time. After the replacement of the new spark plug, the failure remains. (3) using tail gas analyzer to detect the tail gas, it is found that the vehicle tail gas is seriously exceeding the standard, CO value is about 3.5%, HC value is 300 x 10-6 ~ 400 x 10-6, and the value of lambda value is 0.8 ~ 0.9V, and these 3 indexes also show that the mixture gas is too strong. But this value is unstable, and it will return to normal after running 2km. At the same time, the exhaust gas is qualified, and only occasionally appears some black smoke when accelerating. Therefore, it can be considered that this vehicle fault is accidental. Therefore, it is suspected that the fuel injector has the possibility of dripping fuel. The balance test of injector, found that 2 cylinder and 4 cylinder injector failed, removed and found internal dirty. The engine works smoothly after changing the new injector, but the exhaust emission is still high. Looking for it carefully, it is found that there is a crack in the vacuum hose leading to the engine oil pressure regulator. Replace the vacuum hose, troubleshooting. Fault analysis: as the internal blockage of the 2 and 4 cylinder injectors and the rupture of the vacuum hose, the fuel pressure regulator is sometimes uncontrolled by the vacuum, which makes the fuel pressure too high and causes oil and black smoke.