Some fixes for a car engine that vibrates while idle include replacing worn-out spark plugs, reattaching disconnected or loose hoses, and ensuring that timing belts are tight and functioning well. Cleaning the components of the fuel intake system and adjusting the idle on a carburettor can also fix engine vibrations.
Faulty or worn-out spark plugs cause the engine to misfire and subsequently result in engine vibrations. Loose hoses may also cause a violent shaking. If the engine vibrates excessively when the vehicle is parked, the motor or transmission mounts could be damaged. Adjusting or cleaning the fuel intake system can increase the efficiency of combustion and reduce engine vibrations.