Inspection and analysis: the maintenance personnel found that the engine was obviously jitter when starting, which was similar to that caused by too dirty throttle valve. No exception was found on the oil cover. Connect the fault diagnosis instrument to read the engine fault code, display the camshaft position sensor fault, active and static. When the engine idling, its work is relatively stable. At this time, the throttle opening of the throttle is read without obvious abnormality. After reading 15 and 16 sets of data, it was found that 4, 5 and 6 cylinders had different degrees of misfire, while 1, 2 and 3 cylinders were 0. The analysis shows that 4, 5 and 6 cylinders are all on fire, indicating that the intake air volume of the left cylinder is insufficient, which may be the failure of the cam shaft phase adjustment function. Troubleshooting: replacing camshaft to adjust solenoid valve, troubleshooting. Additional Description: this vehicle is not a line fault of solenoid valve. If it is, the system will give the fault code of circuit break / short circuit.