Why does the car idle with a slight shake when cold?
3 Answers
The reasons for slight shaking during cold idle: 1. The car's engine oil, transmission fluid, brake fluid and other various fluids are not warmed up, and the water temperature hasn't risen yet - the entire vehicle is cold; 2. Poor combustion in the cylinders, which leads to insufficient power output from the engine, causing the car to shake. Idling is an operating condition of a car where the engine runs in neutral gear. The engine speed during idling is called idle speed. When adjusting idle speed, the RPM shouldn't suddenly increase or decrease, otherwise it may cause premature wear to the engine. Idle speed can be adjusted by modifying the throttle opening size. Idling essentially means the engine is running but not doing any work.
Last week in cold weather, my car also had unstable idling and shaking upon startup, feeling like the engine was trembling. When the engine is cold, the lubricating oil thickens, increasing piston movement and bearing friction. Combined with aging spark plugs or excessive carbon buildup, the air-fuel mixture burns unevenly, causing an imbalance in output force and resulting in shaking. The ignition coil is less efficient at low temperatures, leading to delayed ignition or misfires, and the battery may also provide insufficient power. If the engine mounts are aged and hardened, their damping effect weakens, allowing vibrations to directly transmit into the cabin. I make it a habit to warm up the engine for a few minutes in cold weather, checking the dashboard for any abnormalities, and regularly cleaning the throttle body and fuel system to prevent worsening carbon buildup. When replacing parts, prioritize inspecting the spark plugs and ignition system. Those with strong DIY skills can check for loose connections or vacuum leaks themselves; otherwise, seek professional diagnosis to prevent engine damage and increased fuel consumption early on.
During my first year of driving, I encountered idle speed shaking in winter and felt nervous as if the car was falling apart. The idle control motor or airflow meter is prone to failure in low temperatures, causing the computer to receive incorrect signals, leading to inaccurate fuel supply and unstable combustion. Carbon buildup in the fuel injectors is also common, resulting in poor fuel atomization and inconsistent cylinder output. Additionally, reduced cylinder pressure or poor valve sealing leads to insufficient compression, exacerbating the shaking. I learned to use fuel additives for cleaning a few times, which slightly alleviated the issue. Regular maintenance should focus on checking sensors like the coolant temperature sensor, as it affects the cold-start fuel supply strategy. Minor shaking that disappears after warming up can be observed, but if it persists or is accompanied by unusual noises, be sure to visit a repair shop to avoid unexpected failures, as safe driving is paramount.
