At idle speed, there is engine vibration. Also intermittent clicking sound. on 1997 Volvo 850

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1) when engine is idling, there is an abnormal loud humming noise and engine vibration. 2) When you brake and car stops, engine shudders slightly. 3) Also when engine idles, there is a clicking sound as if some kind of relay is coming on and off. It is a continuous sound.
(1) Answer
have alternator tested. engine may be trying to shut down when extra load put on electrical(alternator), thats why the shudder and vibration. is a possibility hope it helps.