Why does the car shake violently when it is just started?
2 Answers
The reasons for severe shaking when the car is just started are poor fuel quality, carbon deposits in the engine valves and intake pipes, and spark plug failure. The specific reasons are as follows: Poor fuel quality: Inferior fuel has poor volatility. When the engine block temperature is low during a cold start, the fuel injected into the cylinders cannot mix sufficiently with air, resulting in difficulty starting and severe body shaking. Carbon deposits in engine valves and intake pipes: Carbon deposits can absorb an appropriate amount of fuel, causing the electronic control unit to misjudge, failing to provide the power needed for the car to start, leading to shaking. Spark plug failure: The gap between the spark plug electrodes gradually increases, reducing ignition energy and causing poor fuel atomization, which results in body shaking immediately after starting.
I know all about cold start engine shaking – my old ride did the same last winter. The most common culprit is carbon buildup in the engine, especially for cars that are 3-5 years old. The throttle body and fuel injectors get clogged like rush hour traffic. Incomplete fuel combustion leads to carbon deposits on piston heads, causing the air-fuel mixture to go haywire when cold. Another issue is a failing ignition system – spark plugs with worn electrodes or leaking ignition coils can prevent proper combustion, making the engine sputter violently. Then there's the silent killer: deteriorated engine mounts. When the rubber cracks like a turtle shell, it can't stabilize the engine, making the steering wheel dance the tango when you rev. If the shaking stops after 10 minutes of warm-up, it's likely carbon buildup – a $50 fuel system cleaning at the shop will fix it. But if it persists after reaching operating temperature, immediately check the ignition coils and engine mount bolts.
