Why does my car shake Just got timing belt changed and now shakes when you stop at a light or sign?

1. Incorrect timing belt tension: If the timing belt is not tensioned correctly, it can cause the engine to vibrate excessively, especially at idle. This is because the timing belt is responsible for synchronizing the movement of the pistons and valves, and if it is not properly tensioned, it can cause the engine to run rough.

2. Worn or damaged timing belt: If the timing belt is worn or damaged, it can also cause the engine to shake. This is because the timing belt is made of a flexible material that can stretch or break over time, and if it does, it can cause the engine to lose synchronization and run rough.

3. Other engine problems: In addition to the timing belt, there are other engine problems that can cause a car to shake when it is stopped at a light or sign. These problems include:

- Vacuum leaks: Vacuum leaks can cause the engine to run lean, which can cause it to vibrate excessively.

- Faulty spark plugs or wires: Faulty spark plugs or wires can cause the engine to misfire, which can also cause it to shake.

- Fuel injector problems: Fuel injector problems can cause the engine to run rough, which can also cause it to shake.

If your car is shaking when it is stopped at a light or sign, it is important to have it diagnosed by a qualified mechanic as soon as possible. This will help to identify the cause of the problem and prevent further damage to the engine.