What is the reason for engine shaking at startup but not while running?

[Rudy]

The reasons for engine shaking at startup but not while running are: 1. Damaged spark plugs, where the wear of the spark plug electrode gap leads to insufficient spark ignition, resulting in incomplete combustion of the air-fuel mixture; 2. Poor quality gasoline, causing poor atomization effect of the fuel injector and incomplete combustion of the mixture in the cylinder; 3. Dirty throttle body or excessive carbon buildup on the fuel injector; 4. Abnormal fuel pump supply pressure or incorrect and malfunctioning intake pressure sensor readings. The function of the engine is to convert thermal energy into mechanical energy by burning and expanding gas in a sealed cylinder, pushing the piston to do work, thereby providing power to the vehicle. The maintenance methods for the engine include: 1. Cleaning the air filter; 2. Removing sludge from the throttle body; 3. Cleaning carbon deposits from the fuel injector.