What Causes Engine Vibration After Starting?
1 Answers
Causes of engine vibration during car startup include severe carbon buildup in the engine, ignition system issues, unstable oil pressure, etc. Slight vibration is normal, but severe cases require inspection at a repair shop. Details are as follows: 1. Severe engine carbon buildup - The most common cause of car vibration is excessive dirt in the throttle body or carbon deposits in the fuel injectors. When excessive carbon accumulates inside the engine, gasoline sprayed by the cold-start injector gets largely absorbed by the deposits, resulting in an overly lean air-fuel mixture during cold starts and making ignition difficult. In this situation, the engine only starts easily after the carbon deposits become saturated with gasoline. After starting, gasoline adsorbed on the carbon deposits gets drawn into the cylinders by engine vacuum for combustion, enriching the mixture. This alternating lean/rich air-fuel mixture causes idle vibration after cold starts. 2. Ignition system issues - Check the condition of spark plugs, high-voltage wires, and ignition coils. Faulty ignition systems or poorly functioning spark plugs can also cause such symptoms. 3. Unstable oil pressure - If you've already cleaned engine carbon deposits, serviced the throttle body, and replaced spark plugs but still experience vibration during startup, inspect fuel supply pressure and the intake pressure sensor. Abnormal fuel pump pressure or incorrect readings/malfunctioning intake pressure sensors can all cause vehicle vibration.
