What does “RPM” mean?
The abbreviation “RPM” stands for revolutions per minute. Simply put, engine speed represents the number of revolutions the engine’s rotating assembly makes in one minute.
As the application of throttle increases, so does the engine’s speed. Similarly, reducing throttle application reduces engine speed. Engine speed is displayed on a vehicle’s tachometer, which is integrated digitally or analogically into the dashboard-mounted instrument cluster.
Most tachometers display engine speed in single digits, but this is a scale measurement and is actually one thousandth of the engine’s actual speed. For example, when the tachometer needle is exactly on the “3,” the engine speed is approximately 3,000 rpm.
Is it normal for the speed to fluctuate when the air conditioner is turned on?
It is normal for engine speed to fluctuate when the air conditioner is on. However, the only time you should notice fluctuations is when the air conditioner compressor is turned on and off. Apart from these periods, the engine speed should remain relatively constant with little noticeable fluctuation.
These slight fluctuations occur when the engine tries to increase the idling speed to overcome the additional load caused by the operation of the vehicle’s air conditioning compressor. This idle drops to normal immediately after the compressor clutch is disengaged.
Is it safe to continue driving with speed fluctuations?
It is important to remember that engine speed fluctuations are related to many underlying conditions, some of which can cause significant driving problems. Therefore, it is best to avoid driving a vehicle that experiences unexplained speed fluctuations unless you are sure that you will not be incapacitated by such problems.
In some cases, continuing to drive in this condition also carries the risk of further damage and mechanical stress. This is most common when there is a major problem with the ignition system, as unburned fuel is sent into the vehicle’s exhaust, which can damage the catalytic converter. The chances of such damage only increase the longer the vehicle is driven.
In all cases, the root cause of your vehicle’s RPM fluctuations should be diagnosed and addressed at the outset if possible. This will avoid the risk of unnecessary damage to your engine and additional expenses. If you are not comfortable completing these repairs yourself, or simply don’t have the time, you should schedule an appointment with a trusted auto repair shop or independent mechanic as soon as possible.
Average Cost to Fix Speed ​​Fluctuations
Fortunately, many of the repairs required to fix this condition are relatively reasonable in terms of overall cost.
However, if there are a number of more complex underlying issues, repair costs can be significantly higher. This is especially true for issues related to your vehicle’s transmission or PCM.
In either case, you can usually expect to spend over $1,000 to get your vehicle back in working order. In certain circumstances, these costs can be significantly higher.
