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A 2009 golden cup sea lion car with a mileage of about 70 thousand km and a 4G20D4 2 L electronically controlled gasoline engine and five speed manual transmission. Users reflect: the engine of the vehicle is not speeded up smoothly, and the exhaust pipe is emitting black smoke. According to the users, the car had been repaired at the fast repair shop before. It had replaced the spark plug, the ignition coil, the air inlet manifold absolute pressure and the temperature sensor, cleaned the fuel injector, and the related wiring harness of the engine electronic control system was checked, but the fault was still on, and the engine barrier lights sometimes lit up when the vehicle was driving. Fault diagnosis: the analysis shows that the engine acceleration is not smooth, the cause of the smoke of the exhaust pipe may be the air flow sensor and its line fault, the oxygen sensor and its line fault, the cooling liquid temperature sensor and its line fault, the air inlet manifold absolute pressure sensor and its line fault, the spark plug working and burning. Oil quality problems and so on. The fault code reads the fault code, and the fault code is "P0105 intake manifold pressure too high / too low", record and try to clear the fault code, the fault code can be cleared. The data flow of engine idle speed is read. The result is that the absolute pressure of the intake manifold is constantly changing from 53 kPa to 68 kPa, the signal voltage is constantly changing from 2100 mV to 2683 mV, the opening of the throttle is 0%, the throttle signal voltage is 585 mV, the battery voltage is 14 V, the intake temperature is 46 C, the cooling temperature is 92 C and the ignition is 92. The advance angle is 5.7 degrees; the engine speed varies from 713 r/min to 875 r/min; the injection pulse width varies from 8.2 MS to 9.7 MS; the idle air control is constantly changing from 42 steps to 47 steps; the voltage of oxygen sensor 1 is 0 mV; the air fuel ratio is 14.00:1. Through the above data flow, it can be seen that the engine mixed gas in the car is in a strong state, and the signal data of the oxygen sensor are also problematic, and it is precisely because the mixture of gas is thicker, and the engine exhaust smoke and acceleration are not smooth and so on. In the process of engine idle speed, the maintenance personnel found that the engine idle speed has a gradual downward trend, sometimes even automatically extinguish. When the engine speed drops, the absolute pressure of the intake manifold and the signal voltage, the injection pulse width and the idle air control data fluctuate greatly, and the absolute pressure of the intake manifold can be from 63 kP. A decreased to 19 kPa, the signal voltage decreased from 2630 mV to 1080 mV, the injection pulse width decreased from 9.5 MS to 5.3 MS, and idling air control dropped from 47steps to 17steps. If the engine accelerates again and again, the engine fault light will be lit again and the smoke will be smoky. According to the hint of the fault code, using the multimeter to measure the absolute pressure of the intake manifold and the related line of the temperature sensor, it is confirmed that the power supply, the iron lap and the signal line are normal. Therefore, it is doubtful that the absolute pressure and temperature sensor that the intake manifold has changed can be unstable. After the consent of the owner, a new intake manifold absolute pressure and temperature sensor was replaced and tested repeatedly, and the malfunction was found to be greatly improved. This shows that the absolute pressure and temperature sensor of the intake manifold replaced by the fast repair shop does have problems. After that, the data flow at idling speed of engine was observed, and the data had been gradually approached to normal data. Only the data flow of oxygen sensor still did not respond. Considering that the engine has been running in a relatively strong mixture of gas for a period of time, the spark plug electrode and the oxygen sensor may have more carbon deposition on the surface of the oxygen sensor, so the car's spark plug and oxygen sensor inspection is removed, and the carbon dioxide in the dismantled oxygen sensor and the spark plug are found to be more carbon. In order to save the maintenance cost, the maintenance personnel carried on the loading test after repeated cleaning of the spark plug and oxygen sensor, and the acceleration performance of the vehicle was obviously improved, and the failure of the exhaust pipe black smoke almost disappeared. The engine idle speed, the absolute pressure of the intake manifold and the signal voltage, the injection pulse width and the idle air control are still somewhat higher, the engine idle speed is 785 r/min to 873 r/min, the absolute pressure of the intake manifold is 39 kPa to 52 kPa, and the absolute pressure of the intake manifold is the absolute pressure. The signal voltage of the force sensor is 1320 mV to 1975 mV, the injection pulse width is 4.9 MS ~ 5.7 MS, the idle air control is 35 steps to 46 steps, and the oxygen sensor has been restored to work, and the signal voltage is constantly changing. So why does the engine run normally and the engine failure light is not bright, but can the relevant data flow be less than normal? After consideration, maintenance personnel suspect that there is a leak in the engine intake system. In the idle state of the engine, after careful listening, there is no air leakage around the intake system; in the state of the engine, the carburetor cleaning agent is sprayed to the seal of the 4 injectors and cylinder heads respectively, and the engine speed has no obvious change. As the data flow is only slightly higher, the maintenance staff decided to remove the injector to check the tightness, because the car had removed the injector cleaning in the fast repair shop before. After removing the fuel manifold fixing bolt, gently pull out the 4 injector, and find that the O ring of the 3 cylinder fuel injector has been broken. Troubleshooting: replace the O ring, the injector is installed after the test, the engine idle speed is stable, the speed is smooth, again the engine idle speed of the data flow, the data flow is also restored to the normal value, so the failure completely eliminated.