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Summary
  • Sudden unintended acceleration is a glitch that happens when the vehicle accelerates on its own without driver input.
  • Driver error such as pedal misapplication is one of the most common causes of acceleration problems.
  • If your car accelerates on its own, try not to panic, hit the brakes, and switch to neutral gear or turn off the engine.

Obviously, having complete control over your vehicle is essential to your safety on the road, so it can certainly be jarring (and frightening) when your car suddenly accelerates by itself while you’re driving. There have been several reports of sudden unintended acceleration in the US over the past few years, and while incidents are few and far between, their consequences have been alarming.

However, most heavily publicized cases of unintended acceleration have not been confirmed. There is yet to be a case investigated by the National Highway Traffic System Administration (NHTSA) where it was proven that an error in the vehicle’s electrical system was at fault.

Federal law mandates redundancy in computers, so automakers incorporate multiple pedal sensor inputs of the same kind—otherwise the vehicle’s throttle control system limits both throttle response and engine speed to either half throttle or idle in cases where pedal sensors fail.

What is Sudden Unintended Acceleration?

Sudden unintended acceleration is a glitch that happens when the vehicle (supposedly) accelerates on its own without driver input. In some cases, drivers also complain of loss of braking ability during an unintended acceleration event.

Over the years, the public has speculated it to be the cause of several crashes involving vehicles from different automakers. Such incidents have brought about recalls of the involved vehicles for the safety of the public and for further investigation.

acceleration car control with pedal
Sudden unintended acceleration is a glitch that happens when the vehicle (supposedly) accelerates on its own without driver input.

What Causes Acceleration Problems?

In most cases, sudden unintended acceleration supposedly occurs when the car is in motion. As mentioned above, although there has been a lot of speculation as to why this can happen, in major investigations, driver error is often found to be the cause.

The problem happens when instead of stepping on the brakes, the driver steps on the gas. Pedal misapplication can easily be avoided by being mindful of where you step.

Things to Consider

Here are other things that might result in sudden unintended acceleration that you should consider:

  • If your throttle is cable operated and you have cruise control engaged and the vehicle begins to accelerate when you’re attempting to slow down, there may be a problem with the brake input to the cruise control system.
  • The notion that using your cruise control in the rain might cause an accident is highly unlikely (although using cruise in the rain isn’t a good idea). The story is that a highway patrolman shared that a vehicle being driven in the rain would slow down and cause the cruise control to apply the throttle, but that won’t happen unless the non-drive wheels are providing vehicle speed information to the cruise control module.
  • If you’ve accelerated aggressively and find that your accelerator has stuck under the floor mat, perhaps the floor mat should be repositioned.
  • Again, auto makers go to great lengths to prevent sudden unintended acceleration from ever happening, and usually when it does happen, it’s driver error.
  • Unfortunately, sometimes the throttle plate will stick in the throttle body due to sludge on cable-equipped throttles, and the pedal may feel very hard and unyielding on acceleration. And if the vehicle happens to be in reverse when foot feed pressure is increased to the point of breaking the throttle body loose from being stuck, the vehicle can experience uncontrolled acceleration in reverse even though the driver’s foot was placed on the brake in order to take the vehicle out of gear.

Note: If your throttle is hard and then “pops” loose regularly, clean the throttle body. But if you decide to clean an electronic throttle body, don’t open the throttle plate with your fingers and don’t put your fingers in the throttle body when your helper is operating the throttle for cleaning. Use some spray and a toothbrush, because an electronic throttle body will cut your fingers off if it closes while your fingers are in there.

Recorded Incidents of Sudden Unintended Acceleration

The first recorded case of sudden unintended vehicle acceleration in the U.S. can be traced as far back as the 1980s, when Audi had to recall 250,000 units of 1978-1986 model 5000 cars. At that time, there were around 271 injuries and 5 deaths recorded involving the Audi 5000.

However, in 1989, investigators found out that these accidents happened due to pedal misapplication—it turns out that Audi’s placement of pedals were different from what car owners in the U.S. were used to, causing them to step on the wrong pedal.

The problem with the Audi came about because those vehicles (and others) didn’t require the brake pedal to be applied to take the vehicle out of gear. The driver would put the vehicle in reverse, and on high idle, the car would begin rapid acceleration backwards, throwing the driver’s weight against the accelerator.

Jeep (and possibly some other automakers) issued a recall on Cherokees to prevent this kind of thing from happening.

In 2010, CNN reported that Toyota recalled around 8.1 million vehicles as a result of the NHTSA’s formal investigation regarding brake problems in the 2010 Toyota Prius. The automaker has since settled 537 claims of serious injuries and deaths allegedly caused by incidents of sudden acceleration in several of their vehicles.

But after investigating the charges against Toyota, it was uncovered that most were just because of loose floor mats. Because of this, a recall was ordered and dealers were advised to update the accelerator pedal assembly to keep the pedal from being entrapped in the floor mat.

Nowadays, the majority of vehicles have clips to secure the driver’s side floor mat.

Suffice to say, there really haven’t been any proven cases of sudden unintended acceleration in the major investigations cited above—but it still helps to be mindful of its “causes” to be safe.

What to Do When Your Car Accelerates on Its Own

Now that you know what causes sudden unintended acceleration, what should you do in case it happens? As a preventive measure, be mindful of the arrangement of your pedals and floor mats. Master their locations and ensure that your foot is hitting the right pedal when you drive.

bothered look of a male driver
As a preventive measure, be mindful of the arrangement of your pedals and floor mats.

Also, see to it that your floor mat is laid out properly and not blocking the accelerator pedal in any way.

Although sudden acceleration is usually attributed to human error, vehicle faults aren’t completely out of the question.

Should you find yourself in this situation, here are some tips:

1. Resist the urge to panic.

It can be difficult to stay calm when you find your car suddenly accelerating on its own. However, you will need a clear mind to get yourself off the road and to a safe place.

2. Hit the brakes.

Step on the brake pedal and hold it with all your might to maximize the vacuum power assist.

3. Go neutral.

Keep your vehicle in neutral as you try to bring it to safety and try to go in a straight line. If you must change lanes, take extra care to manage your movement better.

However, if your vehicle won’t shift to neutral, turn off the engine immediately.

gear shifter on neutral position
Keep your vehicle in neutral as you try to bring it to safety and try to go in a straight line.

4. Make sure the key is in the ignition.

This will prevent your steering wheel from jamming once your engine is turned off.

5. Ask for help.

Once you’ve safely parked your vehicle, call an automotive professional to help you fix it.

If you find your car accelerating on its own, check if you’re actually stepping on the right pedal before considering it a probable case of unintended acceleration.

You might just not be aware of the exact placement of your brake pedal. Also, check if your floor mats are getting in the way of the pedals or causing your foot to slip as you move your foot between the brakes and the gas.

If you’ve confirmed that it wasn’t a mistake on your end or with the floor mat, and you’re still unsure about what caused your car to accelerate on its own, have an expert mechanic take a look.

Where to Get New Throttles

If your vehicle accelerates too much on its own, then it’s best not to drive it until the problem has been addressed. Depending on what’s causing the issue, you might need a replacement throttle to fix the issue. Fortunately, getting a replacement that fits your vehicle is easy with CarParts.com.

We have new and remanufactured throttle bodies for various makes and models. To view compatible parts, enter your car’s details into our vehicle selector.

All our parts are on hand and ready to ship from a warehouse near you, so you can get what you need in as fast as two business days. We source our throttle bodies from the most trusted brands in the industry to ensure they’re built to last. They come at competitive prices, so you don’t have to break the bank to fix your ride.

Don’t underestimate acceleration problems. Order the replacement parts you need today to resolve them.

About The Author
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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Brian

NHTSA has never proven UA because they lie in there reports to the benefit of the manufactures. I have investigated UA many times and even after NHTSA looked and said they could not find anything. The NHTSA does not look they dont care then they lie to cover things up.

I have investigated plenty of cases and found obvious proof of mechanical UA, Electrical UA and pedal entrapment.

Every case is different but this the drivers are all lying is a bunch of hype. Some likely do lie but not all of them. The problem is the government does everything to minimum standards and follow the money. It is very easy to say we did not observe any thing that contributed to UA when you never look.

Barb

Agreed, and that includes mechanics and insurance adjusters. We need to challenge their integrity and hold them to account.
I was recently in an accident that caused my van to jump over a parking block and then collide into a building. The assumption was that I stepped on the gas instead of the brake, but I had my foot positioned over the brake the entire time. I had asked a mechanic to look at my van. He told me everything was fine. Said he drove it around the block a couple of times. I asked if he had checked out my electrical, he gave me a weird look and shook his head.
My first instinct in every incident has always been to brake, even when I panic. Other experienced drivers would agree. This had me second-guessing myself.  Are we being gaslighted here?
You would have to be inexperienced, addled, drunk or stoned, or just plain stupid to step on the gas instead of the brake. Yes, I believe that UA is more common than these guys say it is.
From the reactions I have gotten, it is perceived that I was either lying, or that I couldn’t recall the incident accurately. So here I am, feeling shamed for something I did not do.
Lesson learned. Getting a mechanic or insurance adjuster (or even anyone else) to believe you is like trying to convince them you saw a pig fly.

brian

Sorry it took so long to reply just noticed your comment. I look at vehicles all the time for UA.

TJ Hessmon

In Newer vehicles, operation of engine speed is controlled by the engine management computer, not the vehicle operator. Yes the operator pushes their foot against a resistance device, called a gas pedal or accelerator pedal, however that pedal does nothing but provide input for the engine management computer. There is no direct link between the drivers foot and the movement of the throttle body valve.

what this means is that unintended or non operator defined acceleration, is specifically an effect unrelated to operator causation. Therefore it is an effect specifically caused by the engine management computer, regardless of what so called experts state.

one can research this issue and discover, that unintended acceleration is more prevalent with drive by wire cars opposed to cars that have an accelerator cable directly connected from the gas pedal to the throttle body. If your car is drive by wire, then its prone to unintended acceleration as well as unintended deceleration, as the engine management computer makes all throttle decisions, not the vehicle operator.

TheUnknownCynic

This actually arises on some vehicles, and is reproducible, as a result of the motor mounts on the driver’s side of the vehicle giving away (being broken).

As you start to accelerate, the engine tends to rotate toward the passenger side of the vehicle, usually restrained by the motor mounts. Absent such restraint, the linkage to the carburetor (or whatever) extends sending more (unlimited) fuel to the engine, thus causing the vehicle to accelerate.

I’m amazed at how many mechanics, insurance companies and accident investigators get this wrong.

Had it. Fixed it. Laundered my trousers…. JK 😂

Amy Adkisson

Just to jump in here, I had this problem occur and the dealership just tried to gaslight me. However, the first time it happened we were on a freeway and the car started accelerating dramatically. Braking did not stop it. Eventually my husband got it into neutral and thankfully we were able to get it safely to the side of the freeway. Turned it off, switched it back on IN PARK with foot on the glass and RPMs pegged. This repeated multiple times. Used the manual to identify potential fuses and that reset it. Got home safely (and washed out our pants) but the problem reoccurred in my driveway a few days later. In park, foot on brake. Mats were not the issue, we triple checked. This was not a driver’s error, and it repeated, in park, both for my husband and myself. Had it towed to the dealer who declared nothing wrong and gave me the pat on the back and “make sure you know which pedal you’re pressing “ talk. I’m not saying that it isn’t ever driver’s error, but stating that it is always drivers error is extremely condescending.

A. Ventura

There’s also tin whiskers that can cause this problem on Camrys . I don’t know the details but you. An good tin whiskers Camry sua or something similar. Also overloading the battery can cause it as well. Apparently amongst other things of course. I think it’s just cheaper to pay the settlements that actually make it to court than do anymore research on the issue since the medias attention on the subject isn’t what it used to be. Even this article condescendingly eludes to the fact that it’s the driver’s error. Heck makes sense since most people that experience this don’t survive to talk about it anyway and when they are liable to get sentenced 15 to life for murder in a botched trial like Mackenzie Shirilla in Strongsville Oho. Her only true crime was wearing slippers so inappropriate footwear to operate a motor vehicle which isn’t illegal unless of course it’s the cause of a wreck.

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