What Causes Severe Engine Shaking During Cold Start?

[McAdaline]

Reasons for severe engine shaking during cold start: 1. Excessive carbon deposits. Severe carbon buildup in the engine cylinders can lead to spark plug blockage and valve clogging, directly causing vehicle shaking during idling. If the car's acceleration performance has significantly deteriorated and the shaking persists, consider performing an engine cylinder cleaning. 2. Fuel supply system malfunction. Unstable fuel pressure can cause inconsistent air-fuel mixture concentration, resulting not only in shaking but also unstable idling. First consider replacing the fuel filter, as prolonged use may cause filter clogging. Then check the fuel pressure bypassing the fuel filter - if abnormal, it may indicate a fuel pump issue. 3. Worn engine mounts. If the engine shaking progressively worsens without corresponding power loss, consider whether it's an engine mount problem. 4. Misfiring cylinders. This is the most common cause of engine shaking, typically caused by issues with ignition coils or spark plugs. If ignition coils malfunction or spark plugs fail to fire properly, the vehicle will experience shaking.