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What RPM Should a Car Idle At?

When it comes to idling RPM, not all cars should have the exact same reading. 

However, there is a certain RPM range in which cars should idle. 

Most cars should idle between 600 RPM and 1,000 RPM. Cars that idle below 600 RPM or above 1,000 RPM may have a mechanical issue that you need to address. Additionally, if the RPM jumps around when idling, this also may be a sign of a bigger problem. 

In this article, I will define RPM, explain how to read RPM in a car, and let you know the general RPM range in which your vehicle should idle. 

I will also give you a few reasons why your car isn’t idling at the correct RPM, as well as some additional information about RPM while driving. 

What Is RPM?

Close-up photo of a car's speedometer and tachometer.

In short, RPM stands for revolutions per minute and lets you know how fast your internal combustion engine is operating. 

More specifically, RPM measures how many times an engine’s crankshaft rotates and the number of times the pistons move in the cylinder in the span of a minute. 

In general, the RPM increases when you press down on the gas pedal and stays stagnant when idling or cruising. 

How Do I Read RPM? 

Your car’s RPM appears on its tachometer, which is usually right next to the speedometer. 

In many cars, especially older ones, the tachometer is an analog dial where the needle moves to show you the RPM. 

These types of tachometers usually measure RPM in units of 1,000. 

Thus, if the arrow on the tachometer reads “1,” your car is running at 1,000 RPM. 

In other vehicles, the tachometer is digital and will tell you the exact RPM in numerical digits. 

What RPM Should My Car Idle At? 

Not every car will idle at the same RPM since different engines tend to idle at different RPMs. 

Additionally, the temperature of the engine, the car’s current altitude, and the type of gas you’ve put in the tank can all affect RPM. 

But, overall, your car should idle somewhere between 600 RPM and 1,000 RPM. 

Why Is My Car Not Idling at the Right RPM?

Close-up photo of a tachometer.

There are a few reasons why your car will idle at an incorrect RPM, and I will go through each of them below. 

Your Idle Air Control Valve Is Faulty or Clogged 

The idle air control valve is what allows you to idle when stopped. 

Without the idle air control valve, your engine would stall every time you stopped because there would be no power, and your RPM gauge would read “0.” 

Thus, if your car is idling at a low RPM, there is a good chance that the idle air control valve is to blame. 

If your idle air control valve is going bad or is blocked, your car will idle at a low RPM, and you will likely notice the following issues: 

  • Your “Check Engine” light comes on
  • Your idle RPM fluctuates a lot 
  • Your engine stalls 
  • Your car shakes when idling

Your Engine Coolant Temperature Sensor Is Not Working Correctly 

If your vehicle is idling too high or low, you may have a problem with your engine coolant temperature sensor. 

The job of the engine coolant temperature sensor is to read your engine’s temperature. 

And your idle air control valve needs this information so that it can set your idling RPM at the correct number to keep your car from overheating. 

But, if the engine coolant temperature sensor is not working how it should, the idle air control valve won’t get accurate information, which can lead to too high or low idling RPM. 

If your engine coolant temperature sensor is bad, you may also notice these telling signs: 

  • Your “Check Engine” light is on 
  • Your tailpipe releases black smoke
  • You have trouble starting your engine
  • Your engine overheats 
  • You have to visit the gas station more often 

Your Fuel Filter Is Clogged

The fuel filter in your car gets rid of impurities in your gasoline. 

But just like your oil filter, the fuel filter can become clogged over time. 

If it does become clogged, your engine won’t get enough fuel, which will lower the fuel pressure. 

Low fuel pressure will lead to less engine power and a low RPM, both when you’re idling and when you’re driving. 

Other signs of a clogged fuel filter besides low RPM include: 

  • You have difficulty starting your engine
  • Your engine stalls 
  • Your car shakes when idling 
  • Your engine misfires 
  • You have to go to the gas station more often 
  • You hear strange noises from the fuel pump 

Your Spark Plugs Are Worn 

You may not think about your spark plugs much, but they are an absolutely crucial part of your engine. 

You see, your engine needs a spark to turn the fuel in your car into kinetic energy so that your vehicle can move. 

And the spark plugs are what give your engine that spark. 

So, if your spark plugs are going bad, your engine will not perform as well as it should, which can cause fluctuations in RPM. 

You will know the spark plugs have gone bad when your RPM fluctuates and: 

  • Your car shakes when idling 
  • Your vehicle does not accelerate properly 
  • Your engine starts making a loud noise 
  • Your catalytic converter goes bad 
  • You have to go to the gas station more often 
  • Your “Check Engine” light comes on

Your Car Has a Vacuum Leak 

In your car, there is a vacuum that connects the engine with the mass airflow sensor, which measures the airflow to the engine. 

But, if there is a leak in this vacuum, the mass airflow sensor will read that the engine has a lower airflow than it actually has, causing the engine to receive too little fuel. 

Too little fuel leads to rough idling and a fluctuating RPM, especially when the car idles. 

If you have a vacuum leak, you may also notice that your engine stalls or hisses, and your “Check Engine” light will likely illuminate. 

What RPM Should My Car Be at When Driving?

There is no set RPM your car should be at when you’re driving. 

However, overall, your car should stay somewhere between 1,500 RPM and 3,000 RPM when driving. 

What RPM Is Best for Changing Gears in a Manual?

Close-up photo of a tachometer of a classic car.

For the best fuel efficiency, your car should be between 2,000 RPM and 2,500 RPM when you change gears. 

What Is the RPM Redline?

On your tachometer, you will notice that there is a point where the lines, and sometimes the numbers as well, turn red. 

The beginning of this area is the RPM “redline.” 

And driving over the redline can damage your engine. 

But luckily, reaching the redline in most cars is pretty difficult, so you won’t have to worry about redlining when you are driving under normal conditions. 

You should keep in mind, though, that if you do hit the redline, you can very quickly damage the internal components of your engine. 

Conclusion 

In general, your car should idle somewhere between 600 RPM and 1,000 RPM. 

If it does not, there is likely an issue with your vehicle.

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