Does Your Car Shake at Idle but Smooth Out While Driving? Here's Why Why Does Your Engine Vibrate at Idle? Noticing your engine shaking or vibrating while idling? This could mean something isn't right under the hood. Here's what might be causing it and how What could be causing a slight whole car vibration when idling? Is your car vibrating when idle? Here's when you should be worried What could be the cause of engine vibration when idling? Steering wheel vibration while idle.