Car Vibrates at Idle? 5 Common Causes (and What to Do)

Published on September 25, 2025

If your car shakes or vibrates when idling at a red light or in your driveway, it can feel unsettling. Sometimes it’s just a minor issue, but other times it’s a warning sign of an engine, fuel, or mount problem. Let’s go over the most common causes of rough idling and what you should do about it.

1. Worn or Broken Engine Mounts (Most Common)

Engine mounts secure your engine to the frame of your car and absorb vibrations. When they wear out or break, the engine’s natural shaking is transferred directly to the cabin, making the whole car feel like it’s vibrating when stopped.

  • Symptoms: Strong vibration at idle that improves when driving, clunking noises when shifting into gear.

2. Dirty or Clogged Fuel Injectors

If your fuel injectors aren’t spraying fuel evenly, the engine can misfire or run rough, especially noticeable at idle. This uneven combustion causes shaking and may be accompanied by reduced fuel economy or a check engine light.

3. Spark Plug or Ignition Problems

Worn-out spark plugs or ignition coils can cause one or more cylinders to misfire, leading to a rough idle. If ignored, this can cause long-term engine damage and higher emissions.

Is the Vibration Only at Idle?

Whether your car shakes only when stopped or also when driving helps narrow down the cause. Use our AI tool to enter your symptoms and vehicle details for a more accurate diagnosis.

Try the AI Diagnosis Tool

4. Vacuum Leaks

Your engine relies on a balanced air-fuel mixture. If a vacuum hose is cracked or disconnected, too much air enters the system, causing the engine to idle roughly and vibrate.

5. Dirty Air Filter or Throttle Body

A clogged air filter or carbon buildup in the throttle body restricts airflow, which can cause rough idling. These are simple maintenance items that can have a big impact on smooth operation.

What To Do Next

If your car vibrates when idling, here are the steps to take before visiting a mechanic:

  1. Check Dashboard Lights: If the check engine light is on, have the codes scanned — this can point directly to the problem.
  2. Look & Listen: Notice if the vibration is worse in gear (Drive/Reverse) versus Neutral or Park. This helps identify engine mounts as a likely cause.
  3. Schedule an Inspection: Tell your mechanic: "My car shakes when idling at a stoplight. Could you check the engine mounts, fuel injectors, and ignition system?"