故障现象一辆2011年出厂的长安铃木新奥拓手动挡轿车,累计行驶里程约为4 000 km,出现发动机怠速运转时发动机室内有异响声的现象。故障诊断首先确认故障现象。起动发动机后怠速暖机至正常工作温度,坐在驾驶室内明显听到发动机室内传来“呜呜…”的响声,并且该声音和发动机抖动频率很接近。接着根据故障现象分析,认为导致故障的原因可能有:曲轴箱 Symptom A Changan Suzuki new Alto manual transmission sedan was delivered in 2011 with a total mileage of about 4,000 km. There was a phenomenon in the engine room with unusual noise when the engine was idling. Troubleshooting First confirm the symptoms. After starting the engine idling to normal operating temperature, sitting in the cab clearly heard the engine room came “hum ... ” sound, and the sound and the engine jitter frequency is very close. Followed by the failure phenomenon analysis, that the cause of the failure may be: crankcase