Audi A6L forward block starts or accelerates at low speed with continuous car phenomenon.
  • Automotive

Hello, teacher. Our factory receives a 2008 year FAW Volkswagen Audi A6L car, carrying a 2.4 L engine, and matching 01T type continuously variable transmission. The car was polluted 2 months ago because of the fault code P178F 000 - hydraulic control valve, and when the car entered the factory, the test fault was a continuous shrug phenomenon in the starting or low speed acceleration. The maintenance personnel have replaced the new valve body, Audi CVT special transmission oil (CVTF), and transmission parts with pressure sensors and other components outside. After that, the adaptive learning value is cleared by the special fault diagnosis instrument, and the P1 78F 000 fault code in the fault memory is used, and then the adaptive matching is tested through the road, and all the normal rear vehicles are delivered. Now that the car has been in normal use for more than 2 months, the user reflects that the original fault phenomenon has appeared again. After the car entered the factory, the transmission and engine and other related systems had no fault storage. Through repeated test, the maintenance personnel get such a failure: when the vehicle starts to accelerate, the speed is about 20 km/h, 30 km/h and 40 km/h, there is a feeling similar to the shift of the AT automatic transmission, not the jitter and the shrug (unlike the failure of the maintenance of 2 months ago), the user may not be able to test the car professionally, Mistaken for fault reappearance, this feeling also occurs when the speed is 50~80 km/h. In addition, the shift feels hot car is more obvious than the cold car, and no matter what position accelerates the pedal, there is this shift feeling. As the vehicle was returned to the factory for the two time, the users thought that the last maintenance was not thorough enough, so the objection to the cost of the maintenance was again raised. But in any case, we must first solve the problem of the current vehicle. Through consultation with peers, colleagues believe that the possibility of clutch, chain transmission parts and even valve problems exist. But the user emphasizes that only 1 key parts can be changed to solve the problem, and if it is a valve problem, the user will not pay for it (because the new body has been replaced before). Excuse me, teacher, can we verify the clutch, valve body or chain drive fault by some test data? Next is to try the valve body first, or do you want to disassemble the transmission directly? According to experience, from the fault phenomenon described by you, the problem should be the clutch, but we must use actual data to prove it. In fact, no matter what part of the problem appears, for Audi CVT transmission, we can all be able to use its dynamic data to analyze and finally lock the fault point. For example, if there is a problem with the clutch itself, we can explain it through twelve sets of data blocks (Figure 1). If the difference between the first two current values is negative or less than 65 mA, it is sufficient to prove that the clutch has been repaired or replaced; on the contrary, if the difference is large, then the clutch itself has no problem. The following is the valve body or the chain drive part. We do not want to be eager to dissolve the disintegration transmission through intuitionistic verification, can use seventh groups, Fifteenth groups and eighteenth sets of data information to lock out the fault range, that is the clutch slip, current value and oil pressure value of the corresponding display. When the fault occurs, if the current value changes smoothly and the oil pressure value fluctuates, it will fully explain the problem of the hydraulic system. If all information is normal, the fault is not inside the transmission. There is also one of the information to pay attention to, that is, the low speed to the medium speed range, when the fault occurs, see whether the engine tachometer pointer also fluctuates. If it fluctuates, it should be explained that this phenomenon is caused by skidding in the clutch engagement, and twelve sets of data can be used to verify the existence of the clutch itself. If it is a clutch failure or repair or replacement, if it is a chain drive failure, it must be disassembled and repaired.

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