What Causes Car Shaking During Start-Up but Normal Afterward?
2 Answers
Car shaking during start-up but normal afterward can be attributed to the following reasons and solutions: 1. Severe engine carbon buildup: Carbon deposits in the engine are the main cause of car shaking. When there is excessive carbon buildup inside the engine, the gasoline sprayed by the fuel injector during a cold start is largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture and unstable idle during cold starts. Regular cleaning of the fuel system, inspection of the idle control valve, and cleaning of the throttle body are necessary. 2. Ignition system malfunction: Excessive carbon buildup on spark plugs or overly large spark gaps can cause ignition failure. It is essential to promptly inspect the wiring and replace the spark plugs if necessary. 3. Fuel pressure issues: Abnormal fuel pump pressure or incorrect readings from the intake pressure sensor can lead to poor fuel pump performance and cause the car to shake. Immediate inspection of the fuel pump and pressure sensor, as well as cleaning of the fuel pressure lines, is required.
Last time I drove a manual transmission car, I always felt the car shaking when starting, as if the clutch wasn't properly engaged. Worn clutch discs or issues with the pressure plate can make starting uneven, especially when you partially depress the clutch to start. This could be due to prolonged driving or frequent city stop-and-go wear. Check the clutch fluid level; if it's low, top it up or replace the components—don't delay, or the transmission could be damaged. When I dealt with it myself, I lightly pressed the accelerator and started slowly to ease the issue, but ultimately, I had a professional adjust the clutch cable, and the car returned to smooth operation. Regular maintenance can prevent this situation.
