The mileage is about 166 thousand km, carrying the 2 L engine and 5 speed automatic transmission of Dongfeng Honda CRV in 2008. Users reflect: when the car is slow to slow down, the engine starts to shake suddenly, the engine jitter seriously when the red light is waiting, then the engine is automatically extinguished, and the engine is started several times after the fire is extinguished. Fault diagnosis: after arriving at the rescue site, starting the engine, the starter runs forcefully, indicating that the battery does not lose power; it is checked with HDS, the failure code is stored, the spark plug works and the jump fire is normal. After preliminary examination, no abnormal condition was found, so the car was towed back to the factory for further examination. The car has been servicing in our factory for inspection and maintenance records. It has been found that the car has always changed its engine oil, and there has been no engine failure. Next we decided to check the fuel supply system. The fuel pressure gauge is connected to the engine. The fuel pressure is 390 kPa (380 kPa ~ 420 kPa normal) and normal; the injector is checked, the fuel injection is good and no leakage. Is the cylinder pressure abnormal? When the cylinder pressure was checked before the pressure was checked, the accelerator pedal was started 1 times, and the engine could barely start the engine, but the jitter was serious; the engine was "broken" test and found that each cylinder was working badly; quickly loosened the accelerator pedal, the engine immediately flameout, slowly loosened the accelerator pedal, and the engine barely idled a moment. After that, it is still automatically extinguished. Measure cylinder pressure, cylinder pressure of each cylinder is about 890 kPa (normal should be not less than 880 kPa), normal. Due to the poor working of each cylinder, it is suspected that there is air leakage in the intake system. Check the air inlet system where there may be leakage. When the vacuum tube is checked, the engine jitter is reduced by clamping the crankcase forced ventilation tube with pliers. The engine data flow is seen, the engine speed is 795 r/min, the intake manifold absolute pressure (MAP) is 76 kPa, the air flow (MAF) is 3.1g/s, the air fuel ratio is 3.1g/s. 294, indicating that the intake volume is too large and the mixture is too thin, resulting in poor engine operation. Further checking the engine data flow shows that the A lift data of EGR (exhaust gas recirculation) are 25 mm, which is abnormal when the engine works and does not work. The EGR valve is removed and it is found that the EGR valve spool has been stuck by carbon deposit and can not be closed. After the failure to remove the cleaning and lubricating EGR valve, the valve core of the EGR valve can be shut down normally, the test car is installed after loading, the engine can start the car and work steadily, and the engine data flow is checked again. The data flow of the engine is 0 mm at idle speed, the absolute pressure of the intake manifold is 27 kPa, the air flow is 2.7g/s, the data are all restored normal and malfunction. Except. Failure analysis: under normal conditions, the EGR valve is not open at starting, idle speed, small load and cold machine to avoid the influence of circulating exhaust gas on engine power, but when engine speed, load and temperature meet certain conditions, the engine control unit controls the EGR valve to open, so that a few parts of the exhaust gas are involved in recirculation. To reduce the content of NOX in the exhaust gas. The EGR valve spool of the vehicle is stuck due to excessive carbon deposition, which makes the mixture of engine idle too thin, resulting in automatic engine stall. For vehicles with high mileage, the treatment of coke can not be ignored. It is necessary to advise the driver to maintain the vehicle regularly and to clean the carbon in the inlet, exhaust system and cylinder.