故障现象:一辆EQ245汽车发动机在各种转速下都发出不正常异响。怠速时,发动机发出“拱拱拱”、“拱拱拱”的撞击声;中、高速时发动机发出“哒哒哒”、“拱拱拱”的异响,响声增大且杂乱。中速作断火试验,“哒哒哒”响声减弱,其中一个缸断火,“哒哒哒”异响明显消失。 分解检查:打开发动机气缸盖及油底壳,发现五缸活塞顶边缘及五缸燃烧室边缘有明显的碰撞痕迹,无积 Symptom: An EQ245 car engine emits unusual abnormal noise at various speeds. At idle, the engine issued “arch arch”, “arch arch” of the percussion sound; medium and high speed engine issued “da da da”, “arch arch” abnormal sound, louder and clutter. Medium speed for fire test, “da da da” sound weakened, one of the cylinder off fire, “da da da” abnormal disappear. Decomposition check: Open the engine cylinder head and oil pan and found the top edge of the five-cylinder piston and the edge of the five-cylinder combustion chamber obvious signs of collision, no plot