What causes Jetta to shake at idle but not when accelerating?

[DiDylan]

Jetta shaking at idle but not when accelerating should be classified as unstable idle speed, usually caused by leaks in the intake pipe and various valves, excessive carbon buildup on valves and intake pipes, malfunctions in sensors and circuits controlling idle speed, or ignition system failures. Below are specific reasons: 1. Unstable idle speed: Unstable idle speed is one of the most common issues in the daily maintenance of electronically controlled engines. Common causes include cracked intake manifolds and poor sealing of the intake manifold. When there is a leak in the air supply system, the engine control unit receives inaccurate intake air signals, leading to misjudgment and resulting in unstable idle speed. 2. Poor combustion: Irregular shaking, mild and not severe, with the most noticeable characteristic being that the shaking frequency increases as the fuel level in the tank decreases. This happens because when the fuel system is dirty, impurities with higher density than fuel settle at the bottom of the tank, making the shaking more pronounced as fuel decreases. The fuel pump draws in these impurities along with the fuel, leading to poor combustion in the combustion chamber, which causes the shaking.