在排除机动车故障时找出该故障产生的可能性最大的一种原因（这里姑且称之为“首选原因”），往往可以收到事半功倍的效果。例如：活塞环对口———气缸套磨损不均匀，即使更换新活塞环，还会出现对口现象；气门摇臂折断———发动机配气相位错乱；发动机捣缸———连杆螺栓断 One of the reasons why it is most likely to find the fault when troubleshooting a motor vehicle (tentatively referred to as the “first choice” here) can often result in a multiplier effect. For example: the piston ring counterpart --- cylinder liner wear uneven, even if the replacement of the new piston ring, there will be counterparts phenomenon; valve rocker arm broken --- engine with gas phase disorder;