What Causes Engine Shaking in Sedans?
3 Answers
Engine shaking in sedans can be attributed to the following reasons: Severe engine carbon buildup: The most common cause of vehicle shaking is a dirty throttle body or excessive carbon deposits in the fuel injectors. When there is 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 and causes idle shaking after a cold start. The lower the temperature, the more fuel is required for a cold start, and the presence of carbon deposits significantly affects the success of the cold start. Ignition system issues: Check the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or inadequate spark plug firing can also lead to such symptoms.
I've been repairing cars for over a decade, and the most common cause of engine vibration in sedans is issues with the ignition system. Burnt spark plugs, aging ignition coils, or leaking high-voltage wires can all cause a cylinder to misfire, making the engine shake like a sieve. Insufficient fuel pump pressure or clogged fuel injectors leading to uneven fuel supply can also easily cause vibrations. A dirty air filter or vacuum leaks in the intake manifold can disrupt the air-fuel mixture, causing continuous engine shuddering. Loose engine mounts or worn rubber cushions can make the vibrations more noticeable. Severe carbon buildup can also interfere with cylinder combustion. When encountering vibrations, start by listening to the engine for smooth operation; if there's no response in a particular area, it's likely a spark plug issue. Fix it promptly, or wear and tear will worsen, costing more. Replacing spark plugs, cleaning fuel injectors, and regular maintenance can prevent most problems—don't wait until a breakdown to act.
Last year, my car's engine was shaking violently, trembling non-stop when starting, and driving felt like riding a horse. After taking it for inspection, the mechanic found that two spark plugs were completely burnt out, and the ignition system was a complete mess. After replacing the new spark plugs, it instantly became smooth again. Sometimes, shaking can be due to an aging fuel pump causing unstable fuel supply, or a clogged air filter restricting airflow. Loose engine mounts or excessive carbon buildup are also common causes. After that experience, I started servicing it every six months to ensure everything is in order. Remember, don't ignore shaking—get it checked promptly to avoid more expensive repairs. Pay attention to whether acceleration is smooth during normal driving, as early prevention saves trouble.
