Q7 "Dangdang" abnormal noise occurs when refueling at low speed

11.9 period

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Trouble phenomenon: Q7 "Dangdang" abnormal sound when refueling at low speed

Model: Q7

Trouble phenomenon:

when refueling at low speed "Dangdang" abnormal noise

failure analysis:

check the appearance and chassis of the vehicle, no abnormal; no installation or modification of the vehicle; no related maintenance history; no fault code storage

Try to reproduce the fault:

a) Drive at low speed, refuel after collecting oil , You can hear the obvious "dangdang" abnormal noise in the cab, and it can be preliminarily judged that the abnormal noise comes from the front of the vehicle. The fault can be reproduced within the range of 20~50km/h, and the fault can be reproduced in the D2~D5 gears. It can reproduce

b) Lift the vehicle with a lift, start the engine, put in D gear, repeat the process of refueling and refueling several times, the abnormal sound of “Dangdang” can be heard many times at the bottom of the engine; open the engine compartment cover, On the upper part of the engine, the abnormal sound of "Dangdang" can be heard more clearly. It is judged that the abnormal sound comes from the upper part of the engine

. Remove the upper cover of the engine air filter and try to reproduce the fault again. The air flaps are all switching between the closed state and the open state. It is inferred that the air intake flap interferes with the left side bellows of the air duct during the state switching process, resulting in "Dangdang" abnormal noise

disconnection The vacuum line of the vacuum valve that controls the switching of the intake flap, try to reproduce the fault again, and the fault is eliminated; reconnect the vacuum line, remove the left bellows of the air duct, and try to reproduce the fault again, the fault is also eliminated; confirm the abnormal sound It is the air intake flap that interferes with the left bellows of the air duct during the state switching and jams, causing

to check the left bellows and find that the interface of the left bellows has warped and deformed, as shown in the figure

Install the bellows of the original car again, and use the manual vacuum pump to drive the vacuum valve action (simulating a fault situation). It is found that the air inlet flap is stuck by the warped and deformed bellows during the switch from the closed position to the open position, as shown in the figure:

Install the left bellows of the normal vehicle without warpage and deformation on the vehicle, and test it again. The air intake flap no longer produces abnormal noise when the air intake is switched. The fault is eliminated.

Solution: Replace the air guide tube

Fault analysis Summary: The interface of the bellows on the left side of has warped and deformed, and the air intake flap interfered with the bellows on the left side of the air duct during the state switching process, resulting in "Dangdang" abnormal noise. 1z