宝马发动机怠速抖动故障维修案例（BMW engine idle jitter troubleshooting case）.doc

宝马发动机怠速抖动故障维修案例（BMW engine idle jitter troubleshooting case） Fault phenomenon: a 2004 BMW E66760Li sedan, users reflect the engine idle jitter, driving weak acceleration, recently appeared after starting the engine have gasoline situation. Troubleshooting: after receiving the car, the author first of all to the user to know whether the car before or after the occurrence of abnormal conditions. Users reflect, some time ago because of the local typhoon, causing the car part of the water. There was no trouble when the water was treated clean. After a period of use, a variety of failures occurred, but most of them were repaired. Only the engine trouble was not repaired. The throttle valve has been cleaned in other repair plants, and the ignition coil and spark plug have not been solved. This car is equipped with a N73 engine, this is a very high technology content of the engine, 12 cylinders are arranged in the V type structure, 4 valves per cylinder, the variable valve control valve is fully electronic technology (Valvetronic) and direct fuel injection technology. The fuel injection system of the N73 engine. The nozzle of the injector is located in the combustion chamber, near the intake valve, and the injector of each cylinder is mounted on the same rail. The fuel rail of each cylinder is supplied by 1 high-pressure pumps, and the high-pressure pump is driven by an exhaust camshaft. The high-pressure pump from the electronic fuel pump fuel pressure, the fuel pressure increased to 5 ~ 12MPa, the compressed fuel through a high pressure pipe to the fuel rail, and then to the fuel injector, the injector by the DME engine control unit according to the signal related to control sensor. Since the pressure of the pressurized fuel is very high, the conventional fuel pressure gauge cannot be used to measure the fuel pressure in the high-pressure line in the general maintenance plant. And from the maintenance manual can be seen that the injector control voltage between 85 ~ 100V