What Causes Car Shaking During Startup?
2 Answers
Reasons for car shaking during startup: 1. Excessive carbon deposits: Severe carbon buildup in the engine cylinders can lead to clogged spark plugs and blocked valves, directly causing shaking during idle; 2. Fuel supply system malfunction: Unstable fuel pressure can cause inconsistent mixture concentration, resulting not only in shaking but also unstable idle; 3. Worn engine mounts: This is a very common cause of shaking. If the engine shaking worsens over time without a corresponding loss of power, the issue might be with the engine mounts; 4. Misfiring cylinders: The problem lies with the engine's ignition coils or spark plugs. If the ignition coils fail or the spark plugs cannot fire for some reason, the car will experience shaking.
When the car shakes during startup, I think the most common causes are ignition system and clutch issues. If spark plugs are carbon-fouled or severely worn after prolonged use, it can lead to uneven ignition, causing the engine to shake; if the clutch disc is worn, engagement during release becomes unstable, and power transmission feels like gear skipping. Other possibilities include loose or damaged engine mounts, which transmit vibrations into the cabin—especially common in older vehicles. I’ve handled many similar cases before, like a ten-year-old car shaking badly, which was resolved after replacing the spark plugs. I recommend first checking the condition of the spark plugs and clutch. If the shaking is severe, stop driving to avoid damaging the transmission or triggering costlier repairs. Safety comes first—don’t underestimate it, as it affects handling and could lead to accidents.
