Question: a Mercedes Benz S600 car has been repaired. The acceleration is bad. One of the engine fault lights will be lit and the fault code is adjusted. The content is multi cylinder fire. The data flow shows the excessive mixture of steam. The air flow meter shows that the value is too high and the fuel consumption is high. Two sets of ignition coils, 24 spark plugs and air flowmeters have been replaced. The test run feels that the vehicle is normal, and the vehicle is delivered to the customer. On the second day, the customer drove the car again, saying that the trouble was still not repaired. The diagnosis is also the fault code. What is the reason? Answer: the analysis may be three yuan catalytic converter, that is, exhaust blockage. Once the automobile exhaust back pressure is too high, the air flow meter or the intake pressure sensor will detect the large intake signal. When the injection pulse width is increased, the fresh air that actually enters the cylinder is insufficient, the mixed steam is too strong and the multi cylinder fire failure is caused. The computer misjudged the air flow meter or the intake pressure sensor signal voltage too high. In addition, the exhaust blockage will cause high fuel consumption, high noise, weak braking, difficult starting and even unable to start, poor acceleration or intermittent acceleration, cylinder fire, mixed steam concentration, and acceleration of detonation. If the vehicle can also speed up, a non corrosive fuel additive can be added to the gasoline tank to repair it automatically. If the vehicle has no normal speed increase, it is serious that the four three element catalyst is dismantled, soaked with water and oxalic acid, and washed with tap water; if three yuan catalytic endoscopy is examined As a result, it is necessary to replace the new parts and check the oxygen sensors for replacement.