Driver And Driving

What RPM (Revolutions Per Minute) Should A Car Idle At?

Mike Cross
Updated October 18, 2020

When it comes to your car, nothing is more important than it’s health. Especially when your engine is one of the key components in making the car function properly. Most car owners may not be mechanically inclined, but one of the major concerns for them is what an appropriate RPM should be for their car.

What RPM Should A Car Idle At?
What RPM Should A Car Idle At?

What is RPM?

RPM stands for Revolutions Per Minute. You will find an RPM gauge located on most cars. Most of the gauges are located to the left of the speedometer.

This gauge will tell you how fast the vehicle’s crankshaft is spinning when your vehicle accelerates or decelerates.

You’ll notice on your RPM gauge that your numbers are labeled 1, 2, 3, and so on. As an example, if the gauge needle reads 2, multiply by 1,000. Your vehicle’s RPM is 2,000.

Why your car’s RPM matters?

RPM is used as a good indicator to use if you happen to be driving a car with a standard transmission. Your RPM gauge will give you a good idea of when you can shift to a higher or lower gear.

Shifting up before your vehicle “red lines” will prevent your engine from becoming damaged. If you downshift before your RPM reaches too low, you will prevent the vehicle from “bogging” or hesitating as it slows down.

Your RPM indicator can also let you know if your transmission has a serious issue. A sure sign of this issue is seeing your tachometer rise and your vehicle cannot shift. Ignoring this problem will cause complete transmission failure.

So what should the RPM for a idling car?

The idle RPM of a car depends on the type of engine your car has. For example, if your car has a 2.0 liter engine, the idle speed should range from 500 to 800 rpm. A ear with a 2.5 liter engine should have an idle speed from 550 to 750 rpm. If you’re unsure with the type of engine you may have, you should be in good shape if the car’s idle speed is anywhere between 600 to 1000 rpm.

What to look for if idle speed is way off?

There are four ways to see if you’re dealing with potential idle speed issues:

  • RPM gauge does not match OEM specification: You should make a note of what the idle speed is based on the OEM’s specification. You can find this on the underlabel of your car. If the gauge reads anything different, you’re looking at a potential issue.
  • Engine idling higher than usual: Bear in mind that not all vehicles have an RPM gauge. For those that don’t, it takes a few minutes to listen to your engine to hear how it functions. If it sounds like it’s turning faster than it should, have a mechanic look it over. They’ll use a special instrument that can test and determine a car’s RPM speed.
  • Your car “jumps”: For automatic transmission vehicles. If you switch it to drive and your car jumps forward, your idle speed is high.
  • Excessive Breaking: If you break more than you should to prevent forward motion in drive, your idle speed is to blame. Normal idle speed will allow you to break with light force.

Common causes of high idle speed

The procedure of correcting idle speed issues depends on the exact cause of the issue. The following includes a list of common causes of high speed idle and the specific parts affected by them:

  • Bad Fuse: The idle speed in most vehicles are controlled by an idle control valve or ICV. A blown fuse can cause the idle air control (or IAC) to malfunction. This alone can cause the idle speed to be higher than normal.
  • Bad Idle Air Control Valve (ICV): Some cars are equipped with an idle air control valve. One of the causes of a valve malfunction is due to excessive carbon build up in a car’s intake manifold.
  • Vacuum Leak: A vacuum leak in an engine can cause high idle engine speed as the oxygen sensor detects a lean operation. The car’s engine computer will try and compensate and thus speed up a car’s idle RPM. If you want to check vacuum leak, using the best obd2 scanner is the good way to do it.
  • Faulty Throttle: A dirty air intake or a cracked intake tube is the common suspect in this situation. A malfunctioning throttle can either a low or high idle and even cause the engine to stall.
  • Faulty Computer: Idle speed is affected if a powertrain control module is not functioning properly.

Can you still drive if the idle speed is wrong?

Short answer: No.

The reason being is that a high idle speed can make your vehicle much more difficult to control. It can also cause unintended acceleration. Even a car with an idle speed of 1,200 rpm is not good. This will make your vehicle difficult to slow down as you are breaking. Another issue is if your foot comes off the break, your vehicle can jump forward. Imagine having to take your foot off the break, only to have your car jump forward, and accidently bump into the car ahead of them. It’s better to pay your repair bill for an idle speed correction than someone else’s bill because of a few dents in their bumper.

Conclusion

A car’s idle speed is something that is often overlooked by most operators. It is important to pay close attention to your car’s RPM while you’re either driving or in park. Your RPM gauge can serve you well in the long run, especially when you may run into potential engine and transmission problems. If you spot any potential issues or concerns regarding your car’s idle speed, you should immediately have a mechanic look it over. Before any parts need to be replace, a mechanic must rule out certain electrical and physical causes. Once a mechanic determines the specific issue, you’ll know exactly which part will need to be replaced.

Mike Cross
Life is too short to drive with stock audio

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