Posted on 7/25/2025
A smooth, steady idle is something most drivers take for granted — until it starts acting up. If you notice your engine's idle speed rising and falling or the car shaking slightly when you’re stopped, it can be both annoying and worrisome. Fluctuating idle speed is a sign that something isn’t quite right under the hood. Understanding the potential causes can help you catch small problems before they become major repairs. What Is Normal Idle Behavior When your engine is idling, it’s running just fast enough to keep itself alive without stalling — usually around 600 to 1,000 revolutions per minute (RPM), depending on the car. A healthy idle should feel stable and consistent. Slight changes in RPM are normal when turning on the air conditioning or using certain electrical systems, but large or frequent fluctuations suggest an underlying problem that needs attention. Common Causes of Fluctuating Idle Speed There are s ... read more