Shaking specifically while the car is stationary with the engine running, that reduces or disappears once you're driving, points to something affecting how smoothly the engine itself is running — most often a worn engine mount, a misfire, or a fault in the idle control system.
Engine mounts are rubber-and-metal components that absorb engine vibration before it reaches the chassis and cabin. As they age and the rubber perishes, they transmit noticeably more vibration through to the car, which is often most obvious at idle when engine speed and vibration frequency are at their lowest and easiest to feel.
A misfire — one or more cylinders not firing correctly — produces an uneven, lumpy idle that can feel like a distinct shake rather than a smooth vibration. Worn spark plugs, a failing ignition coil, or a vacuum leak are common causes on petrol engines.
This component regulates how much air bypasses the throttle at idle to keep engine speed steady. A dirty or failing valve can cause the idle speed to hunt up and down, producing a shaking or surging sensation while stationary.
A cracked vacuum hose or a poorly sealed intake component allows unmetered air into the engine, upsetting the fuel-air mixture specifically at idle, when the engine is most sensitive to this kind of disruption, often producing a rough, shaking idle alongside a higher-than-normal idle speed.
Injectors that have become partially clogged with deposits can deliver fuel unevenly across cylinders, an effect that's most noticeable at the low, steady fuel demand of idle rather than during normal driving.
On some vehicles, a slight shake or shudder that appears only when the air conditioning is switched on, particularly at idle, is caused by the compressor clutch engaging and adding load to the engine. This is usually harmless, but a compressor with a failing internal bearing can produce a more pronounced vibration or noise that's worth having checked if it's new or worsening.
Shaking specifically at idle, that eases once you're driving, most often points to a worn engine mount, an engine misfire, or a fault in the idle control or vacuum system.
Yes, engine mounts are specifically designed to absorb vibration before it reaches the cabin, so as the rubber perishes, noticeably more vibration comes through, especially noticeable at the lower engine speeds of idle.
Not always, but a lumpy, uneven idle alongside the shake is a strong indicator of a misfire, whereas a smoother but stronger vibration points more toward an engine mount.
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Get My Free Fault ScanLast reviewed 2026-09-08 by the MotorLoom editorial team.