What Causes High Idle Speed and Shaking in Cars?
4 Answers
Car high idle speed and shaking can be caused by: 1. Dirty throttle body; 2. Faulty spark plugs; 3. Non-functioning engine cylinders; 4. Aging rubber components in engine and transmission mounts. The car engine is the device that provides power to the vehicle, determining its power performance, fuel economy, stability, and environmental friendliness. Idle speed refers to the engine running without load, needing to overcome internal friction resistance without outputting power externally, maintaining the minimum stable operating speed. The idle speed is adjusted by modifying the throttle opening size and idle fuel supply quantity.
I once experienced high idle speed shaking while driving, with the engine RPM noticeably higher than normal and the car shaking violently. The mechanic later told me that this is usually caused by excessive carbon buildup, especially when the throttle body and fuel injectors get clogged with sludge, leading to poor air intake and aggravated engine shaking. Worn-out spark plugs are another common issue—if the ignition is uneven, the idle speed tends to become unstable. Another factor is a faulty idle control valve, which is responsible for maintaining idle RPM. Once it fails, the RPM fluctuates erratically. It's advisable to first check if the air filter is dirty yourself. If the problem is severe, it's best to visit a professional shop for a thorough cleaning. After all, delaying repairs can affect fuel efficiency and even damage the engine's core components. I must say, regular maintenance is truly important to prevent such issues.
As a car enthusiast, I usually enjoy studying vehicle conditions. High idle speed with shaking is most commonly caused by issues in the ignition system. For example, spark plug erosion or ignition coil breakage can lead to ignition failure and severe engine vibration. The fuel system is also often problematic - clogged fuel injectors or unstable fuel pressure can cause improper air-fuel mixture ratio, resulting in high idle speed and shaking. Another common issue is intake air leaks, such as cracks in the intake pipe allowing excess air to enter, which affects idle speed control. Additionally, if the electronic control unit (ECU) receives incorrect sensor data, the idle speed value might be incorrectly adjusted. In such cases, it's best to use a diagnostic scanner to read trouble codes rather than guessing blindly. Prompt repairs can prevent accelerated engine wear, and performing pre-drive checks can save you a lot of trouble.
From my experience in car repair, high idle speed and shaking can have many causes. For example, a faulty throttle position sensor can cause the idle speed to go out of control, or spark plugs with too large a gap can lead to uneven ignition and shaking. A malfunctioning oxygen sensor can send abnormal feedback signals, causing the RPM to surge. A stuck idle control valve is also common, preventing it from maintaining a stable idle speed, and carbon buildup on the valves can directly cause unstable operation. The usual solutions are cleaning the relevant components or replacing worn parts. Don't ignore these issues, or the engine's performance will deteriorate faster.
