What Causes the Engine to Shake at Idle but Stop Shaking When Slightly Accelerated?
3 Answers
When the engine's idle excitation frequency couples with the natural frequency of the steering system or the vehicle body, it causes idle resonance, resulting in shaking. When the throttle is slightly pressed, the engine's excitation frequency changes and increases, avoiding the natural frequency points of the drivetrain or certain components of the vehicle body, thus eliminating the shaking. Below is some relevant information: 1. Cause of the Issue: If you notice slight shaking or deviation of the vehicle body while driving, it is usually caused by tire-related problems. First, it could be due to poor tire balance, requiring the owner to promptly perform a four-wheel alignment and dynamic balancing. If the vehicle does not pull to one side, simply performing tire dynamic balancing may suffice. 2. Reason for Wheel Rim Deformation: This condition generally occurs in older vehicles. Typically, when replacing new tires or wheel rims, a tire balance should be performed. Otherwise, uneven weight distribution can easily cause the steering wheel to shake. Vehicle body shaking can affect driving comfort and handling judgment.
I've found that car shaking at idle is usually caused by some common minor engine issues. For example, worn spark plugs or excessive carbon buildup can affect combustion efficiency, leading to unstable low-speed operation. When you press the accelerator slightly, the engine speed increases and fuel injection volume rises, improving combustion stability and reducing the shaking. Other causes may include clogged fuel injectors or a dirty throttle body - these issues might be masked during acceleration. It's important to regularly check spark plugs and clean carbon deposits, preferably performing maintenance every 20,000-30,000 kilometers to prevent minor faults from worsening and affecting driving safety. If the shaking continues to intensify, it's better to visit a professional repair shop for diagnosis rather than waiting until more serious problems occur.
I've encountered a similar issue where the car shakes at idle but smooths out with light throttle. This is often caused by ignition system failures, like worn spark plugs or faulty coils, leading to misfires at low RPM. Alternatively, a dirty air filter restricting airflow can cause uneven combustion at idle due to insufficient air, which balances out when airflow increases during acceleration. Checking is simple: pop the hood to inspect if the spark plugs are blackened, or try cleaning the throttle body. I recommend developing a monthly inspection habit to prevent minor issues from escalating. Additionally, ensuring the fuel system is clean before long trips can also reduce such vibrations.
