What Causes the Engine to Shake Every Few Seconds at Idle?

[DelGavin]

Engine shaking every few seconds at idle is most commonly caused by a misfire. Here are the relevant details: 1. Causes of Misfire: There are many factors that can lead to a misfire. For example, issues with the ignition system—check the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or weak sparking from the spark plugs can also cause this type of issue. The solution is to check if the spark plugs have excessive carbon buildup and replace them if necessary. 2. Severe Engine Carbon Buildup: The most common reason for car shaking is a dirty throttle body or excessive carbon buildup in the fuel injectors. When there is too much carbon buildup inside the engine, the gasoline sprayed by the cold-start injectors can be largely absorbed by the carbon deposits, resulting in a lean air-fuel mixture during cold starts and making the engine difficult to start.