There was a "chug" sound behind the car when it turned off. don't know why

The sudden noise of exhaust pipe may be mainly caused by excessive carbon deposition in throttle, air inlet, air inlet and combustion chamber.

Due to too much carbon and dirt in the air inlet, the cross-sectional area of the air passage changes, which makes the control unit unable to accurately control the idle intake air volume, resulting in too rich or too thin air mixture, abnormal combustion or engine jitter, and even unable to start after starting.

Check the throttle idle motor for excessive carbon deposit, and check the ignition coil and cylinder pipeline for fire failure.

Whether the exhaust pipe joint leaks water or not.