Why does the car shake severely when starting?
2 Answers
Reasons for severe shaking when the car starts: 1. Engine mechanical failure, such as uneven cylinder pressure in each cylinder; 2. Intake system failure, such as excessive carbon deposits on intake valves and intake pipes, excessive dirt on throttle valves and intake pipe inner walls; 3. Engine management system failure, such as incorrect coolant temperature and intake air temperature signals, wiring faults; 4. Ignition system failure, such as excessive carbon deposits on spark plugs or incorrect gap, leakage in high-voltage wires and distributor caps, damaged ignition coils; 5. Fuel supply system failure, such as injectors not closing tightly or being blocked due to excessive internal gum and carbon deposits in the nozzles.
I've got plenty of experience with car shaking during startup. After driving a taxi for over a decade, veteran drivers all know this issue. For manual transmissions, the most common cause is clutch problems - a warped pressure plate or worn friction disc will cause severe shaking during semi-engagement. Worn engine mount bushings are also very noticeable, especially in older vehicles where the entire front end shakes with engine vibration. Also check if the spark plugs are misfiring - if one cylinder out of four isn't working properly, the car will jerk during acceleration. I recommend first inspecting the clutch assembly, then having a mechanic use a diagnostic tool to check for any cylinder misfire trouble codes. By the way, a damaged CV joint can also cause clicking noises along with shaking during startup - don't overlook this possibility.
