What Causes Shaking in Automatic Transmission Cars at Low Speeds?

[DelCali]

Introduction to the causes and solutions for shaking in automatic transmission cars at low speeds: 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 is too much carbon 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 and making it difficult to start. In this situation, the car will only start easily once the carbon deposits have absorbed enough gasoline. After starting, the gasoline adsorbed on the carbon deposits is sucked into the combustion chamber by the engine's vacuum, making the air-fuel mixture too rich. The engine's combustible mixture fluctuates between lean and rich, causing idle shaking after a cold start. The lower the temperature, the more fuel is needed for a cold start, and the presence of carbon deposits will significantly affect the success of the cold start. Solution: Clean the fuel system and check if the idle control valve has carbon buildup, which should be cleaned if necessary. Ignition System Issues: Check the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance in the ignition system or weak sparking from the spark plugs can also cause such issues. Solution: Check if the spark plugs have excessive carbon buildup and replace them if necessary. Unstable Fuel Pressure: If you have already cleaned the engine carbon deposits, throttle body, replaced gaskets, and spark plugs but still notice shaking at idle, it is recommended to visit a 4S shop to check the fuel supply pressure and the intake pressure sensor. Abnormal fuel pump pressure or incorrect readings and poor performance from the intake pressure sensor can cause the car to shake. Solution: Check the fuel pressure and replace components if necessary. Aging Engine Components: Car shaking can also be related to the aging of engine mounts (also known as engine supports). Engine mounts are part of the engine's vibration damping system, responsible for absorbing minor vibrations during engine operation. If the engine mounts are faulty, these vibrations will transfer to the steering wheel and the cabin, causing shaking at idle. Solution: Replace the components.