Why does a new car shake severely during cold start?
4 Answers
Reasons for severe shaking during cold start: 1. Low ignition energy causing vibration. When the engine temperature is too low, both fuel and lubricant temperatures are low. During cold start, a richer air-fuel mixture is required, which in turn demands higher ignition energy. Excessive spark plug gap or aging ignition coils/high-voltage coils can all lead to decreased ignition energy, resulting in vehicle shaking. 2. Incorrect air-fuel mixture ratio causing cold start vibration. When certain engine sensors provide significantly erroneous signals, the ECU makes incorrect judgments, leading to errors in fuel injection timing and ignition timing control, which manifests as engine shaking. 3. Uneven cylinder conditions causing engine vibration. In multi-cylinder engines, significant differences in ignition energy between cylinders may occur. Additionally, varying degrees of piston and piston ring wear result in inconsistent compression ratios, causing uneven power output and engine shaking.
My brand new car has been shaking violently during cold starts, as if the engine is dancing. This could be related to several common issues, such as minor problems with the ignition system, loose or improperly installed spark plugs, or the need for the new car to go through a break-in period. Additionally, slight carbon buildup or uneven fuel injection in the fuel system, like in the injectors, can cause unstable combustion when the engine is cold. Combined with low oil temperature and poor fluidity, this can worsen the shaking. Another factor to consider is poor-quality gasoline containing impurities, which affects the formation of the air-fuel mixture. I recommend first checking the spark plugs and fuel filter. If the shaking persists frequently, take it to the dealership for a comprehensive diagnosis immediately. Don’t ignore it to avoid more serious wear or increased fuel consumption.
Having driven for over a decade, cold start vibrations are not uncommon in new cars. This is usually caused by insufficient internal engine lubrication or issues with the ignition coils. During cold starts, the air-fuel mixture burns unevenly, and if the spark plug gap is too large or the fuel injection is inaccurate, vibrations are more likely to occur. New cars might have assembly tolerances, such as slight throttle sticking or initial sensor calibration deviations. I would recommend letting the car warm up for a few minutes after starting—if the vibration lessens, it's fine, but if accompanied by unusual noises, it's worth checking the oil viscosity and battery voltage. Regular maintenance is crucial, and using the right oil can reduce the likelihood of this issue.
I'm very interested in how cars work. Cold start shaking mostly comes from air-fuel ratio imbalance. New car sensors like oxygen sensor deviations may cause the ECU to misjudge fuel injection quantity, or there might be minor intake manifold leaks affecting air intake uniformity. New engine mounts are initially hard with poor vibration damping, and low temperatures worsen combustion instability. The ECU needs time during the cold-state adaptive learning period - if there are program bugs or excessive fuel impurities, shaking will be amplified. It's best to use diagnostic tools to read codes and check sensor and fuel pump conditions.
