What Causes Car Shaking Upon Startup?
2 Answers
Reasons for car shaking upon startup: 1. Poor fuel quality: Inferior fuel has poor volatility, especially during cold winter temperatures. During cold starts, when the engine block temperature is low, fuel atomization becomes difficult, resulting in insufficient mixing of fuel and air in the combustion chamber. This leads to difficult startups and severe body shaking. 2. Carbon buildup in engine valves and intake manifold: Carbon deposits can absorb certain amounts of fuel, causing the electronic control unit to make incorrect judgments. 3. Spark plugs: During cold starts when both fuel and lubricant temperatures are low, the engine requires more fuel to generate sufficient power. This causes the electrode gap in spark plugs to gradually widen, reducing ignition energy and worsening fuel atomization, consequently causing body shaking.
I've been driving this car for about seven or eight years and have encountered the issue of shaking during startup several times. The most common cause is problems with the ignition system, such as worn-out spark plugs or damaged ignition coils, which lead to uneven cylinder ignition and significant engine vibration. Another reason is carbon buildup on the fuel injectors or throttle body, affecting the combustion efficiency of the air-fuel mixture, causing the car to shake during startup. During cold starts, poor gasoline fluidity can also easily cause shaking, especially when using low-quality fuel in winter. I once ignored this issue, which resulted in increased fuel consumption and nearly caused the car to stall on the road. Fortunately, I made it to the repair shop in time to replace the spark plugs. I recommend regularly checking if the engine mounts are loose and cleaning carbon deposits, especially for cars over five years old—don’t let minor issues turn into major failures. Simply replacing the air filter can also solve some of these problems.
