10 Possible Reasons Your Car Vibrates When It's Idle

By: Kris LeSueur   |   08 Apr 2024

If you're experiencing vibrations while your car is idling, it's time to figure out what's causing the shake. The RPM gauge, also known as the tachometer, measures the rate of revolutions per minute produced by the engine. During idle, the engine completes about 10 revolutions or more per second. A normal idle should measure around 1,000 revolutions per minute. When the RPPM falls below this or shoots up way higher than the normal range and you car shakes,  it’s a sign that something is wrong.

Common Causes of Rough Idle

1. Worn Spark Plugs

Spark plugs play a crucial role in igniting the air-fuel mixture in the engine's cylinders. As they wear out, they can lead to incomplete combustion, resulting in engine misfires and vibrations. Regularly replacing spark plugs can help maintain smooth engine operation.

 2. Damaged Engine Mounts

Engine mounts serve to dampen engine vibrations and keep it securely in place. When these mounts become worn or damaged, they're less effective at absorbing vibrations, leading to noticeable shaking throughout the vehicle.

3. Fuel System Issues

Issues within the fuel system, such as clogged fuel injectors or a dirty fuel filter, can disrupt the air-fuel mixture, resulting in rough idling and engine vibration. Regular maintenance, including fuel system cleaning and filter replacement, can help prevent these problems.

 4. Air Intake System Problems

The air intake system plays a vital role in supplying the engine with the air it needs for combustion. A clogged air filter or malfunctioning idle air control valve can restrict airflow, causing irregular engine idle and vibrations.

5. Vacuum Leaks

Vacuum leaks occur when there's an unintended opening in the engine's vacuum system, allowing excess air to enter the engine. This disrupts the air-fuel mixture and can lead to rough idling and engine shaking.

6. Faulty Oxygen Sensor

The oxygen sensor monitors the oxygen levels in the exhaust gases and provides feedback to the engine control unit (ECU) to adjust the air-fuel mixture accordingly. A faulty oxygen sensor can cause the ECU to receive inaccurate readings, resulting in engine misfires and vibrations.

7. Throttle Body or Sensor Issues

The throttle body regulates the amount of air entering the engine, while the throttle position sensor communicates the throttle's position to the ECU. Issues with either component can disrupt the air-fuel mixture, leading to engine vibrations.

 8. Catalytic Converter Problems

A malfunctioning catalytic converter can restrict exhaust flow, leading to increased backpressure and engine performance issues. In severe cases, this can cause noticeable shaking and vibration throughout the vehicle.

 9. Damaged Engine Belts

Drive belts and timing belts play a crucial role in driving engine components such as the alternator and water pump. Worn or misaligned belts can cause irregular spinning, resulting in engine vibrations and shaking.

10. Faulty Alternator

The alternator is responsible for charging the vehicle's battery and providing power to electrical components. A faulty alternator can result in irregular power supply to the engine control unit (ECU), leading to erratic engine idle and vibrations.


Now that you have a better understanding of the potential causes of engine vibration at idle, it's essential to address these issues promptly to ensure a smoother and more enjoyable driving experience. Regular maintenance and timely repairs can help keep your car running smoothly and prevent further damage down the road. If you're unsure about diagnosing or repairing any of these issues, don't hesitate to consult with a qualified mechanic for professional assistance.

Contact Us

Main: Leave us a voicemailSales: Leave us a voicemailService: Leave us a voicemail
or send us a message

Give us a call or click here to send us a message!

Main: (480) 389-3664
Sales: (480) 787-2375
Service: (480) 389-3735

1109 E Curry Rd, Tempe, AZ 85281