Why does the Vios engine shake when parked?

[HectorFitz]

Vios engine shaking when parked may be caused by the following reasons: Intake system failure: Excessive dirt on the throttle body or intake manifold, or a clogged air filter element reduces the cross-sectional area of the idle channel. This results in less air entering the cylinders than normal, causing the air-fuel mixture to become too rich, incomplete combustion in the cylinders, and ultimately engine shaking. Intake pipe or EGR valve leakage: When more air than normal enters the cylinders, the air-fuel mixture becomes too lean, reducing cylinder power output. If the EGR valve doesn't close properly, some exhaust gas enters the cylinders, increasing residual exhaust gas volume and worsening combustion conditions, leading to reduced engine power and consequent shaking.