Why is My Car Accelerating By Itself: EXPLAINED

If you are driving down the road and your car starts accelerating by itself, it’s a situation that none of us wants to be in. Just shift your car from a gear into neutral and start braking until you come to a complete stop. Your car can also start revving while in neutral or in park on its own. Here is why this is happening:

”If your car starts accelerating by itself it could mean only one thing: If your older model car starts accelerating by itself its because the throttle cable is stuck. If your newer model car starts accelerating by itself its because the computer sensor that makes the throttle open is faulty.”


Why is My Car Accelerating By Itself

The older and newer model car accelerator systems are built differently.

Older Model Car Acceleration

Why is My Older Model Car Accelerating By Itself

If your older model vehicle starts accelerating on its own, its always a simple thing like stuck accelerator cable. When you step on the accelerator pedal, it just pulls a cable that opens the throttle. So, if the vehicle starts accelerating by itself, the throttle cable is stuck. You could pick the gas pedal up with your toe. Just get your foot under the pedal and pick it up to stop it from accelerating. Then, you could either lubricate the accelerator cable or replace it.

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Late-Model Car Acceleration

Why is My Late Model Car Accelerating By Itself

If you look at a late-model car engine you’ll notice they don’t have any accelerator cables. That’s because instead of using a cable, they use computer sensors and electric motors to make the throttle open. So, when you step on the accelerator pedal, you’re actually operating a computer sensor.

The computer sensor is located at the top of the gas pedal and that computer sensor tells the computer how far you’ve stepped on the gas and it sends a signal to an electric motor on a throttle that opens the throttle that far to make it go that fast. So, if there’s a problem in the computer system of the car, it can unintendedly accelerate.

To have a better understanding on how car’s function, here is a detailed article on car parts, their location and function.

What To Do if Car Keeps Accelerating?

What To Do if Car Keeps Accelerating

If your car starts accelerating by itself, do not panic. There is an easy way to get yourself out of that dangerous situation.

1. Shift To Neutral
What To Do if Car Keeps Accelerating - Shift To Neutral

The first that you want to do if your car starts accelerating by itself is to shift to neutral. Once the transmission is in neutral it will no longer be physically connected with the engine. Meaning, the engine is no longer sending power through the transmission to the wheel so it can’t accelerate anymore.

2. Apply Brakes
What To Do if Car Keeps Accelerating - Apply Brake

Once you cut the power supply, its time to start applying brakes like you would normally do to stop. At this point, the engine is revving but it is not accelerating. Even though you will hear loud noises from the engine, do not turn your vehicle off because you will lose power brakes and power steering and you don’t want that. Just apply the brakes to come to a complete stop and then turn off your vehicle.

3. Turn on Hazard Lights
What To Do if Car Keeps Accelerating - Turn on hazard lights

If your car starts revving and accelerating while you are driving in an quiet street, you can stop without worrying about traffic. But, if your car starts to act weird while you are on the highway, its a different story. You could have cars coming from all sides. That is why it’s important to turn on your hazard lights. Once the drivers around you see that you have the hazard lights on, they will know that something is wrong and will make room for you.

4. Take Safety Measures
What To Do if Car Keeps Accelerating - Take safety measures

Again, if you are in a quiet street, no worries. But, if you are in the highway, make sure that you put the warning triangle to let know the drivers that your vehicle is parked. Also, if you have a fluorescent jacket in your vehicle, put it on. Once you placed the warning triangle, move away from the highway and call a tow truck.

Is Sudden Acceleration Bad For Car?

Sudden acceleration can be bad for cars because once your vehicle starts accelerating the RPMs will increase and your vehicle will do a mechanical over-rev. A mechanical over-rev is when your engine RPMs are close or above the red line which will cause a collision between the valve float and pistons because the valve float is still closing and the pistons are rising faster than normal.

What is the red line? Simply put it’s the maximum speed in RPMs that your engine can run safely without causing damage to itself. This is typically denoted by a red line or red section on your tachometer. Red line is usually set significantly below the RPMs of which your engine can actually withstand. The red line varies with a lot of factors including component weight stroke and the displacement of your engine.

You’ll notice that diesel engines typically have a much lower red line than gasoline engines.

Igor Iwanowski

I am a certified Automotive Service Excellence (ASE) mechanic since 2018. I specialize in Brake systems, dashboard warning lights, EGRs, general engine problems, EVAP and Emissions issues.

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