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RPM Fluctuates While Accelerating: The Common Causes Behind It

RPM Fluctuates While Accelerating

When you take a look down at the tachometer in your car when you’re driving down the road in it, it’ll let you know how hard your engine is working to propel your car forward. It’s in charge of keeping track of your engine’s RPM, or revolutions per minute. Generally speaking, the RPM should stay consistent as long as you don’t increase or decrease the speed of your car dramatically. But every so often, you might notice that your RPM fluctuates while accelerating in your car. This could potentially be a cause for concern depending on what’s causing it. Learn more about why this happens and find out how you can fix the issue below.

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What Is RPM?

Before we begin breaking down why you may have noticed that your RPM fluctuates while accelerating in your car, it’s important for you to understand what RPM is. Otherwise, it’s going to be difficult for you to wrap your head around why you need to get your car’s RPM under control. It’s also going to be tough for you to pinpoint what is causing your RPM to fluctuate so much when you push down on your gas pedal.


RPM is, as we mentioned a moment ago, short for revolutions per minute. It’s a measurement that is used to illustrate how many times each of the pistons that are situated in your car’s engine go up and down as well as how many rotations that the crankshaft in your engine makes each minute. Your car keeps track of RPM on the tachometer positioned on your dashboard, and you’ll usually notice the RPM going up or down based on how fast you’re driving your car.


Ideally, you want your RPM to stay relatively consistent when you’re driving around in your car. You don’t want to see that your RPM fluctuates while accelerating or decelerating in your vehicle. You also don’t ever want to see your RPM creep up above the red line on your tachometer. If it does, it could result in serious damage being done to your car’s engine before long.

What Is a Normal RPM When Accelerating?

You don’t have to sit and stare at your tachometer when you’re driving in your car. You should keep your eyes on the road as often as you can. But every now and then, you should check it out to make sure that your RPM is within the normal range as you drive. This range differs from one car to the next, but in general, having your RPM hover between 1,500 and 2,000 when you’re driving at a consistent speed is a good benchmark.


You shouldn’t worry too much if it occasionally goes higher or lower than that. But you should be worried if you see that your RPM fluctuates while accelerating in your car. If your tachometer is telling you that your RPM is bouncing up and down as you build up speed, that’s going to be something that you’re going to want to address sooner rather than later. There could be a number of things causing this to happen, and you’re going to want to get to the bottom of it so that you’re able to bring your RPM back into the normal range again.

When an RPM Fluctuates While Accelerating, What Could Be Causing It?

There are actually quite a few things that could cause your car’s RPM to fluctuate while you’re accelerating in it. You’ll want to carefully consider which of them might be putting you into a situation where your RPM fluctuates while accelerating. More often than not, you’re going to want to let a mechanic look at your car to determine it. But it’ll help you to know what some of the most common causes are. Here are some of the things that present problems for drivers.

1. Bad Idle Air Control Valve

Oftentimes, when your RPM fluctuates while accelerating, it’s going to be because of an issue with the idle air control valve, or IAC, in your car. The IAC is in charge of controlling the idle speed of your engine, and it could be the reason why your tachometer is out of control right now.


The IAC is powered up by a computer mechanic in your car, and if there is a problem with the IAC, it’ll usually lead to communication issues between your engine and your car’s main computer. This can lead to your car stalling out when you’re idling, and it can also lead to your RPM fluctuating wildly when you’re driving. You’re likely going to see that your RPM fluctuates while accelerating when you have a bad IAC.


In many cases, you’ll simply need to have the IAC cleaned to stop this from happening. Carbon buildup can often cause problems for the IAC in a car. But there is also a chance that your IAC might be cracked or damaged, in which case you’ll have no choice but to replace it. It’ll be the only way to get your RPM to stop fluctuating as you drive your car.

2. Vacuum Leaks

There is an engine vacuum that exists in your car that is responsible for many of the most basic functions within your vehicle. For instance, the engine vacuum is what’s used to maintain the right balance of air and fuel flowing through your engine. It’s what allows the proper combustion to occur within your engine so that your engine can do its job and keep your car moving in the right direction at your desired speed.


As you might imagine, this can put you into a tough spot if you ever experience an engine vacuum leak. This type of leak will mess with the air/fuel ratio and throw it all out of whack. You’ll start to see that your RPM fluctuates while accelerating when this is the case. You might also find that your engine will begin to stall out on you when you’re driving it at lower speeds.


An engine vacuum leak is not something that you want to try and fix on your own. It can be very complicated trying to find and fix a vacuum leak. It’s also not something that you’re going to want to linger for very long. If you ever suspect you might have a vacuum leak, you should spring into action right away and have it repaired.

3. Worn-Out Spark Plugs

While the engine vacuum in your car keeps the air/fuel ratio at the right level, the spark plugs in your car are in charge of igniting the air/fuel mixture in your engine so that combustion can occur. With this in mind, it’s not hard to tell what an important part your spark plugs play in the overall well-being of your car, in spite of the fact that they’re some of the smallest parts in your vehicle. If your RPM fluctuates while accelerating, it could be because your spark plugs have gone bad on you.


Worn-out spark plugs can cause misfires to occur within your engine, and those misfires can lead to your engine vibrating a whole lot. Those vibrations can lead to the RPM in your engine going haywire on you. And this problem is only going to get worse over time as your spark plugs inch closer to dying out on you.


If you’ve been driving around with the same spark plugs for more than 30,000 miles, they’re likely to blame for the RPM issues that you’re having. You’ll want to have them tested and then replaced if they’re on their last legs. This should stop your RPM from fluctuating so much while you’re accelerating in your car.

4. Faulty Throttle Pedal Position Sensor

The throttle pedal position sensor, or TPS, in your car has two important jobs. First and foremost, it keeps an eye on the position of your throttle pedal at all times. But at the same time, it’s also in charge of controlling how much air is allowed to flow into your engine as you drive your car down the street. As a result, a bad TPS can cause all kinds of complications for you and your vehicle, which is why you don’t ever want to get caught driving around with one.


When your TPS is faulty, it can lead to your car accelerating on you even though you’re not pressing down on the gas pedal. It can also result in you noticing that your RPM fluctuates while accelerating your car. Because of these potential consequences, a fault TPS is going to cause your car’s check engine light to come on. And you shouldn’t ever ignore it if you believe a bad TPS to be to blame for your RPM troubles.


There are a bunch of components within your car that will need to be disassembled to get to your TPS to replace it. It’s why you should leave the replacement of a TPS up to an experienced mechanic. They’ll be able to remove it from your car and put a new one in its place. This should stop you from seeing your RPM fluctuate while accelerating in your car.

5. More Serious Engine Problems

Most of the problems that we’ve talked about thus far are relatively minor in nature. You’re not going to have to pay an arm and a leg to get them fixed. But you could possibly have a bigger problem on your hands than you might think when your RPM fluctuates while accelerating. There are lots of different serious engine problems that could result in issues with your RPM.


There could be a problem with the combustion process within your engine. There could also be a problem with your engine’s ability to deliver power to the rest of your car. Whatever the case, engine problems are not to be ignored. They’re usually going to result in your check engine light coming on and staying on until you have them fixed. You should seek the services of a trusted mechanic as soon as you can to diagnose the problem with your vehicle.

What to Do When the RPM Fluctuates While Accelerating in Your Car

The second that you notice your RPM fluctuates while accelerating, you should begin thinking about taking it to a mechanic. Your tachometer is basically going to be letting you know that there is some kind of issue bubbling beneath the surface within your engine. You’re going to want to diagnose it and address it as fast as you can to stop it from getting to be any worse.


In a lot of cases, the only thing you’ll have to do is swap out your old spark plugs for some new ones. This is a quick fix and will get your RPM back under control. But in the event that you have more serious engine problems, you’ll have to think about what you want to do next. You may want to go ahead and make engine repairs if you plan on keeping your car, but you may also want to think about getting rid of your car to avoid having to make costly repairs to it. Either way, you’ll want to do something to it to avoid putting yourself into a potentially dangerous situation.

Can You Sell a Car If the RPM Fluctuates While Accelerating?

Let’s say that you notice that your RPM fluctuates while accelerating in your car and you drive it down to a mechanic to get a diagnosis. They tell you that there are serious problems with your car that need to be fixed and that they wouldn’t recommend continuing to drive around in it. But in order to make those repairs, you’re going to have to pay hundreds and maybe even thousands of dollars, which is more than your car is even worth. Then what?


You’re free to pay to have the repairs done if you want. But you should know that you can also sell a car, even if the RPM fluctuates while accelerating. Cash Cars Buyer will pay you cash for your car and take it off your hands for you, no matter what kind of condition it might be in. You should strongly consider going in this direction as opposed to paying to repair your car or continuing to drive around in it. Contact us today to find out exactly how much you might be able to get for your old car.

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