What Causes Severe Engine Shaking During Car Startup?
3 Answers
Reasons for engine shaking during car startup include: severe engine carbon buildup, ignition system issues, unstable oil pressure, etc. Minor shaking is normal, but if the shaking is severe, it's necessary to visit a repair shop for inspection. Below are detailed explanations: 1. Severe Engine Carbon Buildup The most common cause of car shaking is a dirty throttle body or excessive carbon buildup in the fuel injectors. When there's too much carbon buildup inside the engine, the gasoline sprayed by the cold-start injector is largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts. This makes starting difficult. Only when the carbon deposits become saturated with gasoline does the car start easily. After starting, the gasoline adsorbed on the carbon deposits is drawn into the cylinder by the engine's vacuum suction and burned, making the air-fuel mixture too rich. The engine's combustible mixture alternates between being too lean and too rich, causing idle shaking after a cold start. 2. Ignition System Issues Check the condition of the spark plugs, high-voltage wires, and ignition coils. Problems with the ignition system or poor performance of the spark plugs can also lead to such symptoms. 3. Unstable Oil Pressure If you've already cleaned the engine carbon deposits, cleaned the throttle body, and replaced the spark plugs but still experience shaking during startup, it's recommended to check the fuel supply pressure and the intake pressure sensor. Abnormal fuel pump pressure or incorrect readings and poor performance of the intake pressure sensor can also cause car shaking.
My old car has been shaking badly when starting recently, feeling like the whole cabin is vibrating. The mechanic later checked and said it was caused by worn-out engine mounts. Engine mounts are those rubber parts that support the engine. Over time, they harden and crack, losing their cushioning effect, which leads to strong vibrations during startup. Additionally, increased spark plug gaps or issues with the ignition coil can also cause uneven ignition and shaking. I suggest observing after starting; if it still shakes, it's best to get it checked and replaced early. Don't delay like I did, which ended up affecting the transmission. Regular maintenance can prevent this, such as periodically checking the condition of rubber parts. After all, safe driving is the most important.
Starting vibration is mostly caused by ignition system or fuel supply issues. I've encountered severe spark plug carbon buildup or clogged fuel injectors leading to incomplete combustion of the air-fuel mixture. Another possibility is a weak battery - insufficient voltage during cold starts results in poor ignition performance. Loose engine mounts can also cause severe shaking. When self-inspecting, first check for abnormal vibrations in the engine compartment and listen for intermittent creaking sounds. Such problems should be addressed as early as possible - replacing small components like spark plugs can restore smooth operation, otherwise it may develop into major repairs costing much more. Remember to pay more attention to replacing these wearable parts as the vehicle ages.
