The driving mileage is about 182 thousand km, the engine model is TU3JP/K, 1.4L, using BOSCH MP5. 2 electronic control injection system Dongfeng Citroen Fukang 988 car, the car for taxi. In the last few days, there was a rapid acceleration of car setback, idle flameout phenomenon, and then stepped on the clutch and stepped on the accelerator pedal. The frequency of the last few days was getting higher and higher, to the repair shop to clean the throttle, the replacement of the spark plug and the injector, and to the Dongfeng Citroen service station for maintenance. Fault diagnosis: after the inquisition to know the above failure phenomenon and the maintenance process, then the maintenance personnel carry on the road test, the road test results coincide with the failure phenomenon stated by the owner. Then parking in situ test, quick acceleration when the car does not reach is, that is, the speed is quickly up to normal, but a loose accelerator pedal is extinguished, and the carburetor engine accelerated pump damage when the phenomenon is exactly the same. According to experience, it is possible to judge the most possibility of the oil road fault, and the particularity of the fault diagnosis of the electric injection gasoline engine. The possible reasons are: (1) the temporary hairpin of the injector does not spray; (2) the intake pipe has a slight leakage; (3) the intake pressure sensor signal is mistaken; (4) the oxygen sensor has a fault; 5. There is a temporary phenomenon of not jumping fire; cylinder pressure is not enough or valve temporary closure is not strict; and so on. The maintenance personnel first check the air intake system carefully, there is no air leakage, and then the replacement of the intake pressure sensor, oxygen sensor, spark plug, no effect, the failure is still. The reason for the replacement of the spark plug is that the engine does not shake at idle speed, and the spark plug will not have problems. This is one of the traditional experiences of the traditional car repair. But the spark plug can jump out of the blue spark in the air and hear the sound of "cracking in the chewing". It is thought that it will apply in the diagnosis of the electric injection engine, which is not appropriate. This does not take into account the high pressure of the EFI gasoline engine, the degree of ionization in the air and the ionization degree of the mixture in the combustion chamber. The spark test in the air does not indicate that spark plugs can jump well in the high temperature and high pressure environment of the engine cylinder. Then the ignition timing was re calibrated, the injector was cleaned and sealed for second times, and the seal was good. Starting test, the failure is still. At this time, the author came to the site of the fault car and suggested that the cylinder pressure test should be done again. The results of the 4 cylinders were around 0. 92MPa (the standard value was 0.93 MPa). It seemed that the cylinder pressure and valve seal were in the normal range. Then the maintenance personnel suggested that the main line of the engine should be replaced, although there was no reason for that, but now we have to try it. Because it is a professional maintenance station, only more than 20 minutes in the same model of the same type of car harness to be removed, starting test, is really disappointing, no effect, the failure is still, and idling when there is a car phenomenon, so the wiring harness is changed. The author proposes to read the data flow. When the engine is idle, the absolute pressure value of the inlet pressure sensor is 340mbar (270 ~ 320mbar), the oxygen sensor changes between 0.1 and 0.9 V (the standard value is 0.1 to 0. 9V), the injection pulse width is 2. 4ms (the standard value is 2.2 to 2.4 MS), which can not be seen from the data flow. What's the problem? Then, the author and the maintenance personnel jointly carried out an analysis, and the conclusion is that, if the intake and exhaust doors are too dirty or the valve is too thick, and the gas in the exhaust valve is too thick, when the gasoline in the mixture is saturated with carbon, there will be a mixture of normal mixture into the cylinder, and the engine has a short time car seat. Back to normal speed. So the maintenance teacher first used the carburetor cleaning agent to spray into the intake pipe, resulting in obvious improvement in the fault phenomenon. Lift the cylinder head down, remove the intake and exhaust valves, and find thick carbon deposits on the intake and exhaust valves. The coke is cleaned and the intake valve is ground, and the exhaust valve is in good condition. After the assembly start test, everything is normal, and the trouble is completely eliminated. Maintenance summary: the trouble of excluding the car has taken a lot of detours. The key is to think too complicated. From another point of view, it is still inexperienced in the maintenance of electronically controlled gasoline injection gasoline engine, and the fault of the vehicle is also special. Therefore, maintenance personnel should strengthen theoretical study in daily work and guide practice with theory. I suggest that the colleagues subscribe to several magazines on automobile maintenance and learn a lot of knowledge and experience in order to improve their professional quality. This is the personal experience of the author for many years. Troubleshooting: Troubleshooting this fault is really a waste of time. Maintenance technicians have changed many spare parts and have not eliminated any failures. The author and the maintenance personnel analyzed the phenomenon, and finally came to the conclusion, but did not explain the process of analysis. In fact, this is very important. In writing this case, the author attaches great importance to what other people have done and fails to elaborate on the cause of the failure. I think the author should have improved it on this point. It is a pity that this article is regrettable. If the author can do this, it will be a very good case of failure analysis. Any fault occurs for a reason, and there is a certain cause and effect relationship between the cause of failure and the failure phenomenon. In the process of troubleshooting, as a maintenance personnel must analyze the causality between the two, in order to understand the mysteries of the problems, but many maintenance personnel are often in trouble and often fail to enter. It is not advisable to replace components with detailed analysis. At present, automobile troubleshooting is no longer entirely based on experience. In the process of troubleshooting, many maintenance personnel did not locate the fault points according to the data, but replaced the components by feeling. For example, the maintenance personnel still use the method of jumping fire when deciding whether to replace the spark plug, and now there is an oscilloscope. As long as the oscilloscope is used to detect the secondary ignition waveform, the problem of the ignition system can be analyzed according to the measured secondary ignition waveform, and the compression of the cylinder can also be determined. Whether there is a problem of mixing gas concentration and so on. If the mixture is too thin, it will react on the ignition waveform, which will cause the spark line to tilt upward. In general, the thinner the mixture, the higher the spark line will be. The excessive mixture of gas also leads to abnormal rough, sawtooth, or strange spark line. According to this, we can analyze the essence of the fault is the problem of excessive mixture gas, then it is very easy to determine the specific fault point.