Why do cars shudder sometimes when idling at a light?

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Why do cars shudder sometimes when idling at a light?

In: Engineering

Usually if your vehicle shudders intermittently or continually while idling , it is being caused by a misfire. Typically misfires are allowed within a certain threshold, exceeding that would trigger a check engine light.

Cars have multiple cylinders that fire in a specific order. Lets say you have 4 cylinders and they fire in a 1-2-3-4 order. Sometimes, the fuel in a cylinder doesnt burn or starts burning early. This causes the shudder.

This is relatively normal if it occurs infrequently. If it happens too often, you will get a check engine light.

There are some good answers here. One other reason is if you replaced the battery recently the computer memory usually gets wiped. It needs to relearn the ideal idle speed. It should correct itself after a while.

Sometimes the car is turning off or turning on the alternator or air conditioner when it’s idling. That reduction or increase in engine load is noticeable when the RPMs are already low from idling.

That third pedal? yeah that’s a clutch. Press it down.