Why Does My RPM Go Up And Down While Idle

Why Does My RPM Go Up And Down While Idle

The RPM or revolutions per minute are supposed to be constant when the car is idle. However, there are times you may notice that the RPM goes up and down even when the car is not in gear.

So, what does this mean? Should you be worried?

It is possible that there may be several things wrong with the car. What is important is that you have it checked to determine what is exactly wrong. Here are ideas on what may cause the RPM to go up and down while the car is idling.

Air leak in the car’s intake

Having an air leak can make the car not have enough boost pressure. This may also lead to the engine backfiring, overheating, and other symptoms. Such would make the RPM go up and down while at idle.

If you can identify the air leak, the engine would not run smoothly.

The throttle body is dirty

The throttle body is quite vital in ensuring your car runs smoothly. That is why you need to keep it clean all the time. The car may still run with a dirty throttle body, but it might have rough idling.

A dirty throttle body also means having acceleration problems. It can be risky driving your car like this, so have it cleaned as soon as possible.

Damaged idle speed control actuator

Your engine has an idle speed control actuator whose job is to regulate the speed of the engine. As such, it is an essential part you do not want to go bad. In case you have a defective actuator, then you end up with rough idling of the car.

Sometimes the car can easily stall if the damage is extensive.

Vacuum leaks

Bad air control and vacuum leaks lead you to an engine having a rough idle. Check the hose supplying the engine with fuel and that of air too to see if there are any leaks.

You should make a habit of replacing worn-out hoses or tightening the loose ones to prevent vacuum leaks.

Malfunction of the EGR System

EGR or Exhaust Gas Recirculation system was designed to help minimize the emissions coming out of the engine. This includes the recirculation of the emissions back to the combustion chambers. Because it is dealing with exhaust gas, this system is likely to end up with deposits of foreign particles.

The foreign particles end up clogging the EGR system making the engine run rough.

Fuel pump malfunction

When your fuel pump malfunctions, you can expect that the car would not be getting the right amount of fuel. So, have it checked to see if it is working correctly before concluding if it is the one causing the error.

Here are a few quick fixes to keep in mind too.


Can faulty plugs affect how the engine runs?

Yes. Having faulty plugs would make the engine idle roughly. Check if they are still in good condition first.

What is the normal RPM for a car at idle?

Most cars would have an idle speed of 600 to 100 RPM.

Will a dirty air filter cause the engine to have a high idle?

Since the air is clogged from getting to the engine, it is likely to have a rough idle and also keep the RPMs higher.

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