汽车频繁强制降挡、行驶顿挫，竟是因为燃油滤清器故障汽车在高负荷的工况下，为了保证动态性能，自动变速箱通常会按需自行强制降挡。下面就让
济南奥迪汽车保养人员来详细讲解这个问题吧。
The frequent forced downshifts and bumps of the vehicle are actually due to the fuel filter failure. In order to ensure the dynamic performance of the vehicle under high load conditions, the automatic transmission will usually automatically force downshifts as required. Let's let Jinan Audi car maintenance personnel explain this problem in detail.
维修人员驾车路试，可以感到车辆的动力偏弱，在试图让车辆正常提速时，不仅加速偏慢而且还会强制降挡，行驶顿挫感是在降挡时出现的。连接诊断仪检测车辆发动机和变速箱系统，并未发现任何故障码。行车时读取变速箱数据，油压、油温、轮速、输出转速等数据也都正常，由此怀疑是发动机存在动力输出不足的问题。
Maintenance personnel can feel that the power of the vehicle is weak during driving test. When trying to increase the speed of the vehicle normally, they will not only accelerate slowly but also force downshift. The feeling of driving stumbling occurs during downshift. Connect the diagnostic instrument to test the engine and transmission system of the vehicle, and no fault codes are found. Read the transmission data while driving, and the oil pressure, oil temperature, wheel speed, output speed and other data are normal. Therefore, it is suspected that the engine has insufficient power output.
回到维修厂，为发动机接入燃油压力表，查看燃油压力数据。起动发动机，怠速时燃油压力正常。踩下加速踏板，让发动机转速升高，燃油压力也相应有所上升。但是当转速升高到3000r/min左右时，燃油压力表的指针就出现了抖动且压力不再上升，发动机运转吃力。显然，当发动机的转速上升后，燃油压力无法满足需求，供油不足，造成发动机难以输出充足动力。
Return to the repair shop, connect the fuel pressure gauge for the engine and check the fuel pressure data. Start the engine and the fuel pressure is normal at idle speed. Press the accelerator pedal to increase the engine speed and the fuel pressure. However, when the rotation speed rises to about 3000 R / min, the pointer of the fuel pressure gauge vibrates and the pressure does not rise any more, which makes the engine difficult to operate. Obviously, when the engine speed rises, the fuel pressure cannot meet the demand and the fuel supply is insufficient, which makes it difficult for the engine to output sufficient power.
通过上述检测得知，发动机在转速升高后，会因为供油不足而动力受限，这时自动变速箱就会强制降挡。正常情况下，强制降挡之初，发动机会补油提高发动机转速，平衡当前轮速和变速箱输出转速的差异，避免出现顿挫。
According to the above detection, after the engine speed increases, the power will be limited due to insufficient fuel supply, and the automatic transmission will be forced to downshift. Under normal circumstances, at the beginning of forced downshift, the engine will supplement oil to increase the engine speed, balance the difference between the current wheel speed and the transmission output speed, and avoid setbacks.
然而，当前发动机得到的燃油量不足，无法拉高转速，就造成了强制降挡后车辆出现明显的顿挫感。导致燃油压力低、发动机供油不足的主要原因有燃油泵故障、燃油滤清器堵塞、燃油管路堵塞，以及燃油压力调节器异常泄压等。
However, the current engine does not get enough fuel and can not pull up the speed, which causes the vehicle to appear obvious setback after forced downshift. The main causes of low fuel pressure and insufficient fuel supply to the engine are fuel pump failure, fuel filter blockage, fuel pipeline blockage, and abnormal pressure relief of the fuel pressure regulator.
本着先简后繁的检查原则，维修人员决定首先举升车辆查看燃油滤清器。检查发现，车上的燃油滤清器比较新，应该是新换的，但从外观看不是正品。将燃油滤清器拆下，发现是没有商标的劣质产品。为车辆换上正品部件后起动发动机，燃油压力恢复正常。
Based on the principle of simple inspection before complicated inspection, the maintenance personnel decided to lift the vehicle first to check the fuel filter. The inspection found that the fuel filter on the car was relatively new and should have been replaced, but it was not genuine from the appearance. When the fuel filter was removed, it was found that it was a poor product without a trademark. After replacing the vehicle with genuine parts, start the engine and the fuel pressure returns to normal.
随后驾车外出路试，车辆加速性能正常、动力充沛，频繁强制降挡和顿挫的情况也不再出现，故障排除。汽车频繁强制降挡、行驶顿挫维修总结劣质燃油滤清器，可能在燃油流通量、泄压阀激活阈值等方面与正品存在较大差异。
After driving out for road test, the acceleration performance of the vehicle is normal and the power is abundant. The frequent forced downshift and setback are no longer occurred, and the fault is eliminated. Summary of frequent forced downshifts, bumps and maintenance of vehicles poor quality fuel filter may be greatly different from the genuine one in terms of fuel flow and activation threshold of pressure relief valve.
Under heavy load conditions such as vehicle acceleration, it is necessary to increase the fuel supply, and the fuel is blocked or relieved at the inferior filter, resulting in insufficient fuel supply for the engine and the speed cannot be increased. You can visit our website for more information http://www.lutongqixiu.com Consult and understand.
