What is the reason why cars emit black smoke?

Common causes of black smoke from automobile engines

(1) The air filter is blocked.

(2) Faults of fuel injectors, such as poor atomization, dripping or high injection pressure.

(3) The fuel system pressure is too high. If the oil return pipe is blocked, the oil supply is too large, or the regulator is faulty.

(4) air leakage.

(5) The vacuum degree is reduced.

(6) The energy of the ignition system is too low.

For example, the spark plug is not firm, which causes carbon deposition and affects the combustion quality.

(7) The valve is not tightly sealed and leaks internally.

(8) Improper adjustment of valve clearance.

(9) The gap between the cylinder and the piston is too large.

(10) The ground wire is poorly grounded.

Causes of black smoke emitted by electronic control of automobile engine

(1) The oxygen sensor is faulty. If the power cord is open and cannot be heated, the oxygen sensor itself is poisoned or unclean. (2) The air flowmeter is faulty. Such as metrology error or misalignment.

(3) There is something wrong with the cold start injector.

(4) The fuel pressure regulator is faulty. If the vacuum hose of the oil pressure regulator is damaged or blocked, it will sometimes cause the regulator to lose control of the vacuum, resulting in excessive fuel pressure.

(5) The throttle position sensor and its circuit are faulty. (6) The intake pressure sensor is faulty. For example, a normal intake pressure signal cannot be provided.

(7) The coolant temperature sensor is faulty. For example, the temperature of the coolant cannot be provided correctly.

(8)ECU computer program failure.

(9) Assembly error. For example, connect the vacuum tube of the intake pressure sensor to the intake manifold (which should be connected to the throttle body).

(10) The grounding wire is poorly grounded. For example, the signal wire of the oxygen sensor is screwed with the shielded grounding wire.

Troubleshooting of black smoke from the engine: black smoke from the exhaust pipe of the engine indicates that the engine is not working normally, and the mixed gas in the fuel supply system is too thick, indicating that the load of the automobile does not match the actual fuel injection. There are many reasons for black smoke in the exhaust pipe, which often involve machinery, oil supply, air intake, electronic control system and so on. Before troubleshooting, first of all, we should analyze the direct or indirect effects of the above systems on black smoke and high fuel consumption, and pay attention to their internal relations, so as to have a clear aim when troubleshooting. The cause of black smoke mentioned above is generally easier to find, but the cause of electronic control is more difficult to find. From the practical experience, the most common cause of black smoke fault of electronically controlled engine is electronic control.

Therefore, when eliminating black smoke, we should pay attention to the following three aspects. (1) Whether the sensor is damaged and the input signal is correct. Damage to the sensor will lead to black smoke failure. For example, after the air flow meter, throttle position sensor, oxygen sensor or other important sensors are damaged, the signals (voltage or frequency) they transmit to the computer can not truly reflect the air flow, thus abnormally increasing the oil supply and causing the mixture to be too rich. Here are two examples.

A BMW 535i car, shortly after wading, appeared the phenomenon of black smoke from the exhaust pipe. The fault code was extracted as normal code, and no abnormality was found in other systems. Check the output signal of the air flowmeter and find that its value is abnormally high. Check the printed circuit board and find that there is an open circuit due to corrosion. After open-circuit welding, the phenomenon of black smoke gradually decreases and finally disappears completely.