What Causes Excessive Shaking and Vibration During Cold Idle?
2 Answers
The reasons for excessive shaking and vibration during cold idle include: incorrect air-fuel mixture, carbon buildup on valves and intake passages, malfunctioning coolant temperature sensor, insufficient ignition energy, unstable fuel pressure, poor fuel quality, incorrect signal from the mass airflow sensor, and malfunctioning exhaust gas recirculation (EGR) valve or control system. Idle is an operating state of a car engine, referring to the engine speed when the car is in neutral gear. The idle speed is adjusted by the throttle opening size, typically ranging between 600 to 800 RPM. Driving idle refers to the state when the car is in gear without pressing the accelerator pedal or when releasing the pedal during driving, maintaining the minimum throttle opening, where the engine speed matches the parking idle speed.
I've been driving for over twenty years, and my car used to shake violently during cold idle, with the entire steering wheel vibrating. There are usually several reasons for this: first, the spark plugs may be worn out or have too much carbon buildup, causing irregular ignition and incomplete combustion, which is particularly noticeable when the car first starts; second, the fuel system may be clogged, such as dirty fuel injectors or a fuel filter that hasn't been replaced for too long, restricting fuel delivery; and there's also the issue of engine carbon buildup, especially impurities sticking to the intake valves, which affects the air-fuel mixture ratio at low temperatures. Additionally, in some older cars, the engine mounts may be worn out, allowing vibrations to transmit directly. Fixing this isn't difficult—I've replaced spark plugs and cleaned the throttle body myself, which doesn't cost much. Regular maintenance is crucial, such as performing carbon cleaning every two years to ensure smooth cold starts. If the shaking persists, it's necessary to check sensors like the coolant temperature sensor for failure. Don't delay addressing this issue, as prolonged neglect can increase fuel consumption and damage engine components.
