Why Does the Engine Idle High and Shake When Cold?

[EdenAnn]

High idle speed and shaking when the engine is cold are primarily caused by carbon deposits in the engine. These deposits can lead the ECU to make incorrect judgments, resulting in insufficient fuel injection. Even if the air-fuel mixture burns completely, it cannot guarantee adequate power output, inevitably causing shaking. Insufficient ignition energy can also lead to idle shaking. Over time, the spark plug gap may widen, reducing ignition energy and affecting engine performance, which results in vehicle shaking. Engine carbon deposits typically manifest as carbon buildup on the valves and intake passages. In such cases, cleaning the throttle body can provide immediate improvement. However, prevention is key. Avoid prolonged idling, occasionally drive at higher speeds, and use reliable fuel cleaning additives to maintain engine health.