Why does the Santana jerk and shake at idle?

[Georgia]

The reasons for the Santana jerking and shaking at idle are as follows: Intake manifold or various valve leaks: When the engine's air intake is incorrect, it can cause the air-fuel mixture to be too rich or too lean, leading to abnormal engine combustion. This results in engine idle shaking. When the leak affects the engine's vacuum level, the engine will shake violently, especially impacting cold idle conditions. Common causes include: aging intake manifold gaskets causing leaks, damaged intake manifolds or other components wearing holes in the manifold, loose or broken vacuum hose connections, and malfunctioning Exhaust Gas Recirculation (EGR) valves that fail to close properly. Excessive carbon buildup in the throttle body and intake passages: When there is too much carbon buildup or dirt in the throttle body and surrounding intake passages, the cross-sectional area of the air passages changes. This prevents the control unit from precisely regulating the idle air intake, resulting in an overly rich or lean air-fuel mixture and abnormal combustion.