What Causes Engine Shaking at Idle?
2 Answers
Engine shaking at idle is usually caused by issues with components such as the ignition system, fuel pressure, throttle body, or fuel injectors. Below are specific causes and solutions: 1. Dirty throttle body or fuel injectors: This is the most common cause of engine shaking at idle. Excessive carbon buildup can prevent fuel from properly entering the cylinders, as most of it gets absorbed by the deposits. This leads to an overly lean air-fuel mixture, making the car difficult to start. After starting, the fuel absorbed by the carbon deposits burns off, causing the mixture to become too rich. This unstable air-fuel mixture results in engine shaking at idle. Solution: Clean the throttle body and remove engine carbon deposits promptly. 2. Ignition system: Key components to inspect include spark plugs, high-voltage wires, and ignition coils. Special attention should be paid to spark plugs—if they are heavily fouled with carbon deposits, replacement is recommended. 3. Unstable fuel pressure: For this issue, it's advisable to visit a 4S shop for diagnosis, as specialized computer equipment is required for analysis. Items to check include fuel supply pressure and the intake pressure sensor. Solution: Inspect fuel pressure and replace any damaged components if necessary.
Having driven for over 20 years, I often encounter severe body shaking at idle, usually due to engine imbalance. Worn spark plugs are the most common culprit—enlarged gaps or electrode erosion cause uneven ignition, making the car shake when moving; worn engine mount gaskets are another frequent cause, reducing vibration damping and transmitting low-speed tremors back to the body. I typically check these two first. If replacing spark plugs myself, choosing the correct model is crucial—poor matching can worsen the shaking. The fuel system is another factor; clogged injectors or unstable fuel pump supply can also cause rough idling. Remember to maintain regularly and clean carbon deposits to prevent issues. When stopped at a red light, avoid aggressive throttle inputs—gentle starts can reduce shaking. In short, body shaking not only affects comfort but may also damage the engine over time—early detection and repair are key.
