Car Won’t Go Above 20-30 MPH? (12 Common Reasons)

It can be frightening and disheartening when your car can’t seem to get motivated.

A problem is definitely apparent if your vehicle doesn’t go any faster than 20 to 30 miles an hour.

Let’s look at why that can be.

We also have an article about why a car won’t accelerate past 60 MPH.

These are some of the primary reasons a car may not go above 20-30 MPH:

1. You have a naughty throttle position sensor.

All the sensors in your vehicle are designed to read information and pass it to the engine’s computer, which prompts it to take action. The throttle position sensor is interconnected to the accelerator pedal to read how heavily you press on the gas.

The computer then sends that information to ensure that you get the proper gas delivery. When a TPS goes bad, it stops reading your foot pedal pressure correctly. So, unfortunately, you may be stuck at 30 MPH because of the glitch.

You can reset the sensor in some cars by removing your foot from the gas pedal. After you do that, you can try turning the ignition key on for two seconds and then turning it off and waiting for 10.

Do that three times, and you might get a Toyota’s sensor to function long enough to drive your car to the nearest automotive shop.

2. Your transmission fluid is extremely low.

Another likely reason your car won’t go more than 30 MPH is that your transmission fluid is almost bone dry. This issue could be due to a leak somewhere in the system.

Stop your vehicle on an even road and leave it running with the parking brake on.

Open the hood and look for your transmission dipstick. Pull it out and wipe it off with a napkin or towel. Repeat the process and then take the reading instead of wiping it off.

You’ve found your problem if the dipstick shows low transmission fluid. Check your operator’s manual for the correct type of fluid to top it off with, and do so as quickly as possible.

Next, take your vehicle to a mechanic who can determine why you have disappearing fluid.

3. Your catalytic converter blocked your exhaust.

Your issue could be a secondary problem caused by a bad catalytic converter.

Maybe the catalytic converter disintegrated, and its debris blocked your exhaust, which would undoubtedly cause your acceleration to be much lower than usual.

You can check to see if your exhaust is blocked by putting the car in neutral and hitting the gas pedal to see how much it revs. Don’t keep your foot on the gas pedal. Instead, just hit it real quick.

You most likely have a blocked exhaust if it dies out or misfires.

4. Your air filter is super clogged.

The air filter is probably the most inexpensive and easily accessible part you have in your entire car. However, it’s the part that most vehicle owners ignore. Its primary purpose is to grab the dust, dirt, and debris so that nothing but clean air will get into the system.

Filters catch so much nasty stuff that they sometimes get dirty and clogged enough to prevent air from getting where it needs to be. The result could be a loss in power that manifests as a 30 MPH limit on acceleration.

Take a few minutes to get underneath your hood to inspect the filter.

You should see a box somewhere in the engine bay that holds the filter. Remove it and look at it to determine whether you need to replace it.

You might see a layer of dirt or dust over it.

Fortunately, you won’t have to spend much if you need to change your air filter. They usually cost less than $20, and you can swap them within minutes.

5. You have a torn air intake hose.

Your loss of power could be due to a torn or leaking intake hose.

The intake hose carries the air to the innermost parts of the engine, and a hole would cause some of the air not to make it to its intended destination.

You can find the intake hose under the hood, and it should look something like a sizeable elbow-shaped piece or have rings on the outside of it.

The unit will most likely have large clamps on its ends that you can remove with a screwdriver. You can generally replace it within five minutes or have a technician do it if you do not want to work under the hood.

6. Your fuel injectors are dirty.

Fuel injectors are small mechanical valves that deliver fuel to the combustion chamber. If these components are clogged or dirty, your combustion chamber won’t get enough fuel, and you’ll see results like a loss of power and low RPMs.

You may also experience sputtering or outright stopping.

One option you have if your fuel injectors are dirty is to buy a bottle of fuel system cleaner. The product may work for it, and it’s typically easy to use.

You will need to pour it into a half-full tank and then run it through your system, and your speed will improve once you do that.

7. Weak Valve Springs

A more serious problem that could cause you not to accelerate past 20 or 30 MPH is weak valve springs.

If your timing is off or your valvetrain has some weak springs, it will prevent your car from going as quickly as you want it to go.

Unfortunately, an issue with your valves is a more serious dilemma than the other problems. You will need to schedule a diagnostic session with a trustworthy auto repair shop that performs engine work to have a specialist work on your vehicle.

Valve work on some models is more labor-intensive than on others, so the costs can vary.

8. Your car has the limp mode feature.

You may experience the effect of Limp Mode if you have a newer vehicle. Limp Mode is a safety and security feature designed to preserve your engine if something goes wrong.

If an issue trips the Limp Mode system, your vehicle will automatically stop running normally until you take it to an automotive shop.

Slow or limited acceleration is a normal symptom that happens when Limp Mode activates.

You’ll need to have your vehicle towed into a reputable auto repair shop for a diagnostic test, which will reveal the problem that set off the Limp Mode feature.

9. You have one or more worn spark plugs.

Spark plugs are crucial components because they’re responsible for keeping the car “fired up,” so to speak. A problem with just one of them will cause a misfire in your engine, and you will lose tremendous power.

You might be experiencing that power loss because your vehicle operates off only a few cylinders. The systems are worse if you only have a four-cylinder car.

Fortunately, spark plugs are not that costly, and you can choose to replace them yourself if you desire.

10. Your gas is of poor quality.

It happens to the best of us. We go to an unfamiliar gas station to fill up when the car runs low, and suddenly, the car won’t accelerate properly. You may have some bad gas if this has happened to you.

The good news is that you can resolve the issue with a good bottle of fuel system cleaner.

Visit your nearest automotive shop immediately and purchase a gas cleaner additive.

They are typically easy to use, as you only need to add the bottle to a half-tank of gas and drive. Hopefully, the cleaner will dislodge the debris or irritant so that your car will run flawlessly again.

11. Your oxygen sensor is acting up.

Sometimes, the sensors in your car go bad and send inaccurate signals to the engine’s computer. The result is a bad mix of air and fuel that prevents the vehicle from operating well.

Your oxygen sensor may be at fault in this situation.

To be sure, you can take your car to a parts store with an OBD2 scanner or visit a repair shop so that they can connect it to an advanced diagnostic system.

12. There’s something under your gas pedal.

Lastly, you might have an object under your gas pedal preventing you from depressing it all the way. The easy fix is to check the area underneath the pedal and remove any obstructive items.

You’ll be well on your way to driving freely after that.

Consider the above situations as the reasons you might be having issues with accelerating past 20 or 30 MPH.

Use the suggested remedies to get your car operating the way it should be.

Always research the automotive shop when you’re thinking about having a mechanic work on your vehicle. You need a trustworthy expert with certifications and plenty of positive reviews.

Sources

Was this article helpful? Like Dislike
Great!

Click to share...

Did you find wrong information or was something missing?
We would love to hear your thoughts! (PS: We read ALL feedback)