What Causes a Sudden Shake During Idle?

[MadisonLee]

Here are the reasons why a car may shake during idle: 1. Severe engine carbon deposits: The gasoline sprayed by the cold start injector can be largely absorbed by carbon deposits, resulting in an overly lean air-fuel mixture during cold starts, making it difficult to start. Solution: Clean the fuel system and check if the idle speed motor has carbon deposits that need cleaning. 2. Ignition system issues: Check the condition of the spark plugs, high-voltage wires, and ignition coils. Solution: Inspect if the spark plugs have excessive carbon buildup and replace them if necessary. 3. Unstable fuel pressure: Check if the fuel supply pressure and intake pressure sensors are functioning properly. Solution: Inspect the fuel pressure and replace components if needed. 4. Aging engine components: The engine mounts act as the engine's shock absorption system, absorbing minor vibrations during operation. If the engine mounts are faulty, these vibrations can transfer to the steering wheel and cabin, causing shaking during idle. Solution: Replace the components.