Why do cars shudder sometimes when idling at a light?

Question

Why do cars shudder sometimes when idling at a light?

In: Engineering

Answer 1

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.