Why Does an Automatic Transmission Car Shake When Starting?
1 Answers
Automatic transmission cars may shake during startup due to the following reasons: 1. The throttle is too dirty, causing uneven air intake and resulting in shaking. 2. Poor fuel delivery, leading to insufficient fuel supply at low throttle, causing uneven operation among engine cylinders and shaking. 3. Abnormal transmission operation. The car shakes during startup but runs normally afterward. 4. Broken or burnt high-voltage wires or spark plug failure, causing some cylinders to misfire and resulting in uneven engine operation and shaking. 5. Check if the battery voltage is within the specified range. The most common causes of car shaking are a dirty throttle or excessive carbon buildup in the fuel injectors. When there is too much carbon buildup inside the engine, the gasoline sprayed by the cold-start injector is largely absorbed by the carbon deposits, leading to a lean air-fuel mixture during cold starts and making it difficult to start. In this situation, the car will only start easily once the carbon deposits are saturated with gasoline. After starting, the gasoline adsorbed on the carbon deposits is drawn into the cylinders by the engine's vacuum suction, enriching the air-fuel mixture. This causes the engine's combustible mixture to fluctuate between lean and rich, resulting in idle shaking after a cold start.
