Jianghuai m5 ran up and turned off the throttle.

Insufficient torque. According to Baidu's query, the abnormal sound of JAC m5 running-in throttle depends on the engine speed state. Abnormal sound is caused by too large clearance between piston and cylinder wall, too tight assembly of piston pin or connecting rod bearing, too large clearance between tappet and its guide hole, worn contour of valve cam, and sometimes loose starting handle, which causes abnormal sound of pulley.