What Causes Engine Shaking and Stalling at Idle?
2 Answers
Engine shaking and stalling at idle can be caused by severe carbon buildup or unstable fuel pressure. Below are detailed explanations: Severe Carbon Buildup: The most common cause of engine 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 injectors can be largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts. This makes the engine difficult to start. Only when the carbon deposits become saturated with gasoline can the engine start more easily. After starting, the gasoline adsorbed on the carbon deposits is then drawn into the combustion chamber by the engine's vacuum pressure, causing the engine to shake at idle after a cold start. Unstable Fuel Pressure: If you have already cleaned the engine carbon deposits, throttle body, replaced gaskets and spark plugs, but still experience body shaking at idle, it is recommended to visit a 4S shop to check the fuel supply pressure and the condition of the intake pressure sensor. Abnormal fuel pump pressure or incorrect readings and malfunctioning of the intake pressure sensor can all lead to body shaking.
Having driven for many years, I've seen plenty of cases where the car shakes at idle and then stalls. Common causes include aging spark plugs failing to ignite, or ignition coil issues leading to unstable engine operation. The fuel system can also be problematic—unstable fuel pump pressure causing interrupted fuel supply, or clogged fuel injectors due to carbon buildup leading to stalling. If the idle control valve gets stuck due to carbon deposits, it can easily cause this, especially noticeable during cold starts. From a safety perspective, if the car suddenly stalls, immediately turn on the hazard lights and pull over—don't force it to keep driving, as it increases the risk of rear-end collisions. You can first check if the spark plugs need replacing or take it to a repair shop for throttle body cleaning. Regular maintenance and attention to these components can prevent such issues, as it can be particularly dangerous if it happens on the highway.
