What Causes Engine Shaking at Idle When Cold?

[JayceLee]

The reasons for engine shaking or vibration at idle when cold are as follows: 1. Excessive carbon deposits. Severe carbon buildup in the engine cylinders can lead to clogged spark plugs and valves, directly causing shaking during idle. The engine needs timely cleaning. 2. Fuel supply system malfunction causing unstable oil pressure, resulting in inconsistent air-fuel mixture concentration. First consider replacing the fuel filter, as prolonged use may clog the filter element. Then check the oil pressure bypassing the fuel filter; if abnormal, it may indicate a fuel pump issue. 3. Worn engine mounts. If engine shaking worsens but power output remains unchanged, suspect worn engine mounts which require replacement. 4. Misfiring cylinders. The problem lies with the engine ignition coils or spark plugs. If ignition coils malfunction or spark plugs fail to fire properly, the vehicle will shake, necessitating spark plug replacement.