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The mileage is about 140 thousand km red flag CA7180A2E car. The engine shakes when the car is running at idle speed, and the engine idle speed decreases from 830r/min to 650r/min after the A/C switch is switched on. All the gears in the driving process have the phenomenon of shrugging, and there are slight tempering and firing phenomenon when speeding up. The fault detection instrument is used to read the fault code, the fault detection instrument shows the normal system, the data flow is read by the fault detector, the idle speed is 4 degrees, the injection pulse width is 2.1ms, the pulse width of the A/C switch is 3.9ms, normal, the cylinder pressure of the 1, 2 and 3 cylinders is above 1.1MPa, only 4 The cylinder pressure of the cylinder is 0.9MPa, and the pressure of the red flag car to the cylinder pressure is more than 0.9 MPa. Because the car has already run 140 thousand km, the above measured cylinder pressure is normal. It is normal to check the secondary waveform and fuel injection waveform with oscilloscope. The spark plug test is used to check the spark plugs, and the spark plugs can be detected at least 3cm, and the spark is blue and white. The atomization test of the injector is carried out by the ultrasonic cleaning machine. The injection amount of each injector is basically the same, and the atomization situation is very good, and there is no leakage phenomenon. At this time, the working temperature of the exhaust manifold of each cylinder is checked with an infrared thermometer. The results are as follows: 1 cylinder is 210 C, 2 cylinder is 220 C, 3 cylinder is 180 centigrade, and 4 cylinder is 108 C. According to the above results, it is not difficult to find that the working temperature of the 4 cylinder exhaust manifold is obviously too low, which is about 100 centigrade lower than that of the other cylinders. Therefore, it is determined that the fault of the vehicle is a mechanical fault of fourth cylinders. Removal of cylinder head revealed that the fourth cylinder intake valve had serious carbon deposition and slight burn marks. As a result, the valve closes badly, and the 3 cylinder intake valve also has serious carbon deposition. After removing the carbon in each cylinder and replacing the intake and exhaust valves, the vehicle is completely eliminated. In order to improve the comfort of the driver, the modern automobile is basically equipped with a warm air air conditioning system, and the warm air air conditioning system is usually composed of warm air, air conditioning, air outlet and so on. All the warm air conditioning systems use the principle of medium circulation and heat exchange inside and outside to achieve the purpose of regulating the temperature inside the compartment. In the process of heat exchange and medium flow, different temperature characteristics will be shown in different places. As the heat releases, the temperature of the medium will be reduced, and the change in the state of the material and the change of physical parameters in the process of circulation flow will also change the temperature, such as the increase of pressure and the temperature. It will gradually rise. In turn, we can indirectly study the internal work of the system by measuring and analyzing the external temperature of the system. Therefore, the infrared thermometer can be used quickly, conveniently and accurately to detect and diagnose the heating air conditioning system of the car. It is more important that your customer can see the trouble you have repaired. By showing the temperature before and after repair, the customer will trust you more. 1. air conditioning system temperature detection one and analysis automobile air conditioning system mainly rely on the compressor to promote the circulation between the evaporator and the condenser. The heat of the evaporator is brought to the condenser by the change of the refrigerant state. The heat is sent to the atmosphere by the condenser and fan, and the air blower is used to make the air flow through evaporation. The temperature of the car is reduced by the entry into the car. There are many factors affecting the performance and effect of the air conditioning system, such as the leakage of the refrigerant, the clogging of the pipeline, the decline of the working quality of the compressor, the control failure of the electromagnetic clutch and the driving skidding, the decrease of the cooling capacity of the condenser and the fan, the weakening of the air supply capacity of the blower and the ventilation duct (air filter, etc.). It also affects the refrigeration capacity of the air conditioning system, at the same time, the sealing condition of the car, the temperature of the environment, the humidity of the environment and the number of passengers in the car also affect the air conditioning effect to a certain extent. When the air conditioning system is tested, it is necessary to adjust the air conditioner control device first to reach the maximum cooling capacity and high speed air blast position, increase the engine speed to 1500 ~ 2000r/min, to measure the air outlet grid temperature of the evaporator, if the air volume is normal at 2~4, and the air volume is not normal by air conditioning filter. As a result of blockage, it indicates that there is no problem in the air conditioning system itself, and the possibility of problems in the sealing and insulation system of the vehicle is greater. Then, the whole refrigeration line can be detected by infrared thermometer in order to verify whether the temperature of each point is consistent with the temperature characteristics of the system at normal temperature. Air conditioning compressor is the core of the whole air conditioning system. It is the driving device of refrigerant circulation flow. It is also the dividing line between high pressure area and low pressure area of air conditioning pipeline, and it is also the boundary of high temperature zone and low temperature zone. The inlet of the compressor belongs to the low pressure and low temperature zone, and the outlet is high pressure and high temperature. Therefore, when the system works, the 2 regions should have a large temperature difference, otherwise it may be the bad work of the compressor. The total temperature of the pipe from compressor to condenser should be basically the same, and the difference of larger temperature is a sign of blockage of the pipe. From the top to the bottom, the temperature of the condenser should be gradually changed from heat (about 70 to 90 C) to temperature (about 50 ~ 65 C), and the temperature change indicates that there is a blockage in the pipe of the condenser. The inlet pipe and outlet pipe of the savings tank / dryer should be at the same temperature (about 50 degrees C); the temperature should also be basically the same from the saving tank / dryer to the expansion valve's liquid pipeline; the expansion valve should be free from frost and the inlet and outlet should have a greater temperature difference; from the evaporator to the compressor part There is a lower temperature (about 5 ~ 10 C). If the temperature of the high pressure area is very high, it is beyond the normal range, and the temperature of the low pressure area is not low to the normal range. It is often caused by the high pressure area pressure too high to cause the compressor to frequently break. At this time, it is necessary to find the cause of the failure as soon as possible, otherwise it will be more dangerous. If the temperature of the high and low pressure tube is just in line with the normal condition, but the feeling in the car is not cool, the cooling of the air conditioning is not a problem, the problem may lie in the temperature regulation system of the air conditioning. Check the heating switch to control whether the pull line is off and check whether the heating water valve is in the closed position. 2. the detection and analysis of the temperature of the warm air system is much simpler than that of the air conditioning system. It mainly introduces the hot water of the engine cooling system into the warm air core, and then blowing the air through the warm air core through the air blower to the car, and it is naturally heated when the air flows through the warm air core. The main reason for the lack of warm (heat) output is the blockage of the warm air. It is possible to diagnose whether the warm air is blocked by comparing the temperature of the warm air input and the output tube. The input and output hoses must be hot, and the temperature of the input tube is about 20 degrees higher than that of the output tube. If the output tube is not hot, it shows that the coolant does not pass through the warm air core, the main reason is the warm air blocking or the heating control valve failure, so the corresponding parts need to be further checked.