Motor mounts keep the engine attached to the car. If the vehicle shakes or the engine shudders a lot when stopped at a stoplight, or when parked with the engine idling, it might indicate the motor mounts or transmission mounts are damaged or broken. To see if this is really the problem, shift the car into neutral.

Why does my car vibrate so much when idling?

While a shaky idling car can certainly feel like an earth-rumbling tremor, it can also indicate a problem with the engine. One common cause of shaking while idling can be loose engine mounts. ... Alternatively, a car that shakes when idle may have faulty fuel injectors, worn-out spark plugs, or a bad timing belt.

Why does my car shake when I'm stopped at a red light?

The more your fuel intake system is clogged, the less efficient your engine uses fuel, which can cause it to shudder when you're at a stop. Fuel is delivered to your engine by fuel intake valves, and these should be cleaned regularly to prevent clogs and a shaky sit at a red light.