Car Not Accelerating When Pressing Gas Pedal

By Sayeed Parvez •  Updated: 03/19/22 •  7 min read

It’s normal for your car to pick up speed depending on how hard you press the gas pedal. But, when this doesn’t happen, the vehicle most likely has acceleration problems. Most times, if your car isn’t accelerating when you press the gas, it could be due to faulty emission, oxygen sensor, or fuel system.

If you just noticed the acceleration state of your car while trying to drive up a hill or move at a very high speed, there are certain faults you should look out for.

Besides, finding the causes will help you know the right fix for the problem. This article will extensively explain 13 major causes of poor/slow acceleration. So, let’s get the ball rolling!

13 Major Causes of Car won’t Accelerate when Pressing Gas

Acceleration problems are common in high mileage cars. Therefore, it’s necessary to check for the issue to make the fix easy. Below are the major causes of a car not accelerating:

Dirty or Clogged Air Filters

The function of an air filter in a car is to provide it with clean air for the air-fuel mixture that’ll be sent to the combustion chambers for burning.

When the air filters are clogged, the engine won’t get enough air to send out the correct air-fuel mixture. This alteration can cause a car not to accelerate.

Malfunctioned Throttle Position Sensor (TPS)

This sensor sends data to the Engine Control Unit (ECU) when it detects the throttle valve opening angle.

When the throttle position sensor malfunctions, the accelerator pedal will no longer be able to control the engine speed, thus making the speed decrease or increase without anyone pressing the gas pedal.

Dirty or Clogged Fuel Filter

Clogged or dirty fuel filters are a major cause of cars not accelerating.

When a car’s fuel filter is dirty, it won’t get enough fuel, thereby causing the car to develop acceleration problems. If this is the culprit, replace the fuel filter to return the car to normalcy.

Timing Belt

This belt is one of the major components of a vehicle’s engine. If this belt gets lost, it can cause serious acceleration problems.

Faulty Catalytic Converter 

When the catalytic converter becomes faulty, it puts so much pressure on the engine. In extreme cases, it could cause the engine to catch fire. This symptom shouldn’t be ignored.

Get the car fixed immediately!

Clogged or faulty MAF Sensor

The mass airflow sensor is connected to the inlet air cleaner. Its function is to calculate and measure the air volume that flows into the air intake.

If the airflow sensor is clogged, it’ll send the wrong data to the engine’s ECU, sending out an incorrect air-fuel mixture.

In the end, a malfunctioning MAF sensor will cause the car not to accelerate.

Limp Mode

Limp mode or limp home mode is when a vehicle refuses to accelerate over 25 or 40 mph.

This mode functions as a preservation feature configured to take you to an auto mechanic, take you home, or off-road without damaging your engine.

Once your car gets into limp mode, you’ll most likely notice a check engine light.

Of course, different factors trigger this mode. However, whatever the cause may be, take your car to a professional mechanic for a checkup.

Failed Clutch

When your car’s clutch fails or the transmission fluid levels become low, it’ll cause acceleration issues.

So, if you notice that your vehicle’s speed changes without you decelerating or accelerating it, troubleshoot the problem or contact your mechanic.

Faulty Transmission Solenoids

It is the transmission solenoids that spark gear changes in automatic transmission to allow the fluid to move and disengage the bands and clutches from the system.

As soon as these solenoids become faulty, your vehicle will develop acceleration problems.

Malfunctioning Oxygen Sensor

The oxygen sensor analyzes the air/fuel mixture ratio of a car by monitoring its exhaust emissions through the engine.

There has to be enough fuel for burning in the combustion cylinders for a car to accelerate properly.

This sensor sends the amount of fuel consumed to the engine’s computer unit.

So, if the O2 sensor malfunctions, the car’s engine will not know the air/fuel mixture ratio to use; this hitch will cause the car to have slow acceleration.

Missing Gears

Low transmission fluid sometimes causes missing gears because of the water contained inside the transmission, contaminated fluid, transmission fluid leakage, or lack of routine maintenance.

This problem can cause your car not to accelerate when you press the gas. In some cases, it could cause your car to have excessive friction.

Engine Control Unit (ECU) Issues

The Engine Control Unit of your car is also known as the computer unit. When there’s system pollution in the car or a build-up of debris, the computer will receive wrong signals of excessive emissions, causing the vehicle to change its air-fuel mixture.

This change will, in turn, cause the car not to accelerate as it’s supposed to.

Worn-out Piston Rings or Valve Seals

The piston rings (2) are the sealing elements on the pistons of the internal combustion engine. The function of these rings (or valve seals) is to block engine oil from entering the combustion chamber.

So, when the valve seals are worn-out, the engine’s combustion chamber will lose pressure and reduce the accelerating power of the car.

Asides from loss of acceleration power, other symptoms of worn-out valve seals are engine misfires, smoke from the tailpipe, and excessive oil consumption.

FAQs

Do I Need to Take My Car to a Mechanic when it doesn’t Accelerate?

The truth is, most of us car owners don’t have first-hand knowledge on how to identify and solve automotive issues. To avoid further problems, if you don’t have experience fixing acceleration problems in a car, kindly take it to a professional mechanic. Don’t hesitate to reach out to your mechanic if you can’t troubleshoot the problem.

Why Is My Car Not Accelerating?

There are many reasons why your car will not accelerate. Most acceleration issues are caused by wear and tear. Also, malfunctioning oxygen sensors, faulty clutch, missing timing belts and gear, dirty or clogged air, and fuel filters can affect the speed (acceleration power) of your car.

You wouldn’t want to risk your safety because of these acceleration issues, so contact a mechanic immediately if you notice these signs. If you’re unsure whether your car has acceleration problems, take your car for regular servicing and maintenance.

What happens when the MAF sensor malfunctions?

When the Mass Airflow Sensor malfunctions or gets dirty, it’ll not send the correct value measurement to the Engine Control Unit (ECU). This improper calculation by the MAF sensor will inject too much or very little fuel into the combustion cylinders. Obviously, this isn’t safe, and your car will begin to decelerate and accelerate without you pressing the gas.

Can a Missing Timing Belt Cause My Car Not to Accelerate?

Of course. Even if it’s just the head of the timing belt that breaks out, your car will start decelerating and accelerating without you pressing the gas pedal. More so, the timing belt is one of the most important components in every car’s engine. Simply put, it functions as the support system of the car, just as the neck supports the head in the human body.

What Do I Do If My Car Suddenly Stops Accelerating Properly?

Fix the car right away! The poor acceleration of your car may not just be because of a clogged fuel filter; the timing belt or gear may be missing. So, to be on the safe side, take your car to an expert mechanic who’ll be able to identify and fix the problem. If you’re familiar with automotive repairs, you can solve the problem.

Final Words

Driving a car that is not accelerating properly is risky. It doesn’t matter whether it’s just the air filter that needs to be replaced. Rather, it’s better to replace the filter immediately than risk your safety.

If you don’t have any knowledge of automotive repair, take your car to an expert mechanic to diagnose the problem and properly fix it.

Additionally, taking your vehicle for regular servicing and maintenance will reduce its risk of developing issues.

Sayeed Parvez