What Causes Car Body Shaking When Starting the Engine?
2 Answers
Car body shaking when starting the engine can be caused by: 1. Unstable oil pressure: Abnormal fuel pump supply pressure or incorrect readings and poor performance of the intake pressure sensor can lead to body shaking; 2. Aging engine components: Engine mounts act as the shock absorption system for the engine, absorbing minor vibrations during operation. If the engine mounts are faulty, these vibrations can transfer to the steering wheel or cabin, causing shaking at idle; 3. Severe engine carbon buildup: Excessive carbon deposits inside the engine can absorb a large amount of gasoline sprayed by the cold start injector, resulting in an overly lean air-fuel mixture during cold starts; 4. Abnormal engine coolant temperature or low cylinder pressure.
Having driven for over a decade, I've encountered numerous instances of engine shaking during startup. The most common cause is carbon buildup clogging the throttle body, leading to unstable air intake at idle. Last time my car shook like a sieve, and upon disassembly, I found all the spark plug tips completely blackened due to ignition coil leakage causing misfires. Another time, the engine mounts had aged, with the rubber cracked like a tortoise shell, allowing engine vibrations to directly transmit into the cabin. Fuel system issues are also frequent culprits—either injector gumming or a clogged fuel filter disrupting smooth fuel delivery, resulting in jerky shaking. I recommend regular fuel system cleaning, checking spark plugs every 20,000-30,000 km, and paying extra attention to engine mount conditions for vehicles over five years old to minimize such occurrences.
