The 2005 Audi A6L 2.4 car with a driving mileage exceeding 224,000 km. User Response: The car accelerated slowly and could not go up at high speed.

　　故障诊断：（1）用VA56150检测有故障码，汽缸列1和2混合气过浓。检查燃油压力正常，喷油嘴无滴漏现象，试更换火花塞及点火线圈无效。分析认为该车已行驶22万，三元催化器堵塞的可能性较大，经检查发现三元催化器确实已堵塞，更换左右三元催化器后试车正常，加速不畅故障排除，但在洗车过程中发现有时起步发冲，小油门加油不走车。

　　Fault diagnosis: (1) First, the fault code is detected by VA56150, and the mixture of cylinder column 1 and 2 is too thick. Check that the fuel pressure is normal and there is no drip leakage in the nozzle. The replacement of spark plug and ignition coil is invalid. The analysis shows that the vehicle has traveled 220,000 kilometers, and the possibility of blockage of the three-way catalytic converter is greater. It is found that the three-way catalytic converter has blocked. After replacing the left and right three-way catalytic converter, the test run is normal, and the trouble shooting is not smooth. However, when found in the car washing process, the car starts to rush and the small throttle refuels the car.

　　（2）再次试车确认，故障发生在低速前进或倒车且打方向时，用5052读取数据块发现混合器调整达25%，仍有偏浓的情况，检查炭罐电磁阀，有关闭不严的迹象，更换后故障依旧。先后又尝试更换喷油嘴、氧传感器及燃油泵无效，替换过节气门、发动机控制单元，故障依旧。读取变速箱数据也未发现异常。

　　(2) Re-test confirms that when the fault occurs at low speed forward or backward and hit the direction, reads the data block with 5052 and finds that the mixer is adjusted up to 25%. There is still a dense situation. Check the solenoid valve of the carbon tank for signs of lax closure, and the fault remains after replacement. It has tried to replace the fuel injector, oxygen sensor and fuel pump ineffective, replaced the throttle, engine control unit, the failure is still. No abnormalities were found when reading the gearbox data.

　　（3）重新调整思路，因故障多发生在低速及打方向的情况下，怀疑是不是发动机功率不足导致。经测量汽缸压力发现4缸、5缸、6缸压力在9bar左右，而1缸、2缸、3缸汽缸压力都在12bar左右，分析3个汽缸气门都出现问题的可能性不大，用内窥镜检查也未发现汽缸有拉伤的迹象，三元催化器已更换过，难道是1列进气有问题？尝试更换进气歧管故障依旧，无奈只得拆检发动机，发现4缸、5缸、6缸活塞的环槽都存在断裂损坏的情况，造成汽缸压力偏低，更换活塞及环后故障排除。

　　(3) Re-adjusting the train of thought, because faults often occur at low speed and direction of attack, it is doubtful whether the engine power is insufficient. After measuring the cylinder pressure, it is found that the pressure of four, five and six cylinders is about 9bar, while that of one, two and three cylinders is about 12bar. It is not likely that the valve of three cylinders will have problems. There is no sign of cylinder pulling by endoscopy. The three-way catalytic converter has been replaced. Is there a problem with intake air? When trying to replace the intake manifold, the engine had to be disassembled and inspected. It was found that the ring grooves of 4, 5 and 6 cylinder pistons were damaged by fracture, which resulted in low cylinder pressure and troubleshooting after replacing the piston and ring.

　　故障排除：更换活塞及活塞环。

　　Troubleshooting: Replacement of piston and piston ring.

　　故障总结：起步发冲等故障也应考虑发动机功率问题。

　　Fault Summary: Engine power should also be taken into account in starting impulse and other faults.