What Causes Engine Shaking When Starting a Car?
2 Answers
Engine shaking when starting a car can be attributed to the following reasons: 1. Severe engine carbon buildup: When there is excessive carbon buildup inside the engine, the gasoline sprayed by the cold start injector will be largely absorbed by the carbon deposits; 2. Dirty throttle body or excessive carbon buildup on the fuel injectors; 3. Engine misfire: This mainly refers to one or more cylinders in the engine not functioning properly; 4. Unstable combustible mixture in the engine, causing idle shaking after a cold start. 5. Additional information: An engine is a machine capable of converting other forms of energy into mechanical energy, which can be used either as a power generation device or to refer to the entire machine including the power unit.
I've been driving for over 20 years and have encountered many instances of engine shaking during startup. Common causes include issues with the ignition system, such as worn-out spark plugs with widened gaps causing uneven ignition, or aging ignition coils with reduced efficiency. The fuel system can also be problematic—low fuel pump pressure or clogged fuel injectors lead to unstable air-fuel mixture and shaking. If the engine mount rubber is cracked, it can't absorb vibrations effectively, making the shaking worse. Severe carbon buildup can disrupt normal cylinder combustion. Last time I had serious shaking, diagnostics revealed a vacuum hose leak, which was fixed by replacement. Startup shaking accelerates part wear, so don't take it lightly—get a full inspection every six months, including cleaning the intake and fuel system.
