Reduced Engine Power – Main Causes & Fix

Do you feel like your car has reduced engine power? Here are all the main causes, what you can do to fix it and how much it costs to repair if required.

The engine is the heart of the car; it produces power and makes your car move. Reduced engine power is something that nobody enjoys.

Potential causes for reduced engine power include a bad throttle body, problems with the MAF and bad fuel pump, transmission failure, and more.

In addition to feeling that the engine does not produce sufficient power, in many cases, the car will notify the driver by either engaging limp mode and/or illuminating the check engine light.

In this guide, we will make sure to make your engine unleash all of its power by solving the problem.

Table of ContentsShow

Faulty Throttle Body

throttle body

Back in the day, wires were directly connected from the pedal to the throttle body. Today that is not the case, instead, much has changed in favor of electronics and computers.

Both modern and older internal combustion engine cars have in common that a physical throttle must be present for the air to move into the engine.

A faulty throttle body will limit the amount of air that can be reached in the combustion chamber and consequently reduce the engine power.

The throttle valve can suffer from carbon buildup leading to the throttle clogging and hindering it from fully opening.

Another cause may lie in any of the sensors, such as the throttle position sensor, which will probably limit the engine power or/and give way to poor acceleration, misfires, or even stalling.


mass airflow sensor

The mass airflow sensor provides information to the car’s ECU about how much air is entering the engine.

In most cases, a bad MAF sensor will lead to constant reduced engine power, which may be more noticeable when accelerating harder than usual, for example, when merging into the highway.

A faulty mass airflow sensor will, in most cases, also produce other types of symptoms, such as a rough idle and poor fuel efficiency.

The problem can be fixed in many cases by cleaning the sensor, but make sure the product you are using for cleaning the sensor is appropriate.

A clean MAF sensor that still produces the same symptoms is due for a replacement, which is not too complicated to do, however, the sensor itself can cost a few hundred bucks.

Bad Fuel Pump

Car Fuel Pump

The task of the fuel pump is to deliver the fuel to the combustion chamber and generate power by igniting the fuel.

Logically, a bad fuel pump will not deliver a sufficient amount of fuel which will directly limit the engine’s power.

In most cases, the problem will be most prominent when there is a greater demand for the engine to produce power, for example, when accelerating, driving on an incline, or driving under load.

If the fuel pump is in very bad condition, the reduced engine power will be noticeable even under less stressful driving situations.

A fuel pump that is bad is due for a replacement. However, make sure that the fuel filter is not the culprit, as a clogged fuel filter will make the fuel pump work much harder and produce similar symptoms.

A good tip to ensure your fuel pump will work properly in the long run is to avoid driving your car with low fuel in the tank as the fuel cools down the fuel pump, preventing overheating.

Transmission Failure

modern automatic transmission

The power from the engine means nothing if the transmission does not transmit it to the wheels.

When it comes to reduced engine power due to the transmission, it is mostly seen in automatic transmissions.

For example, if the transmission fluid has not been replaced or filled up according to schedule, it may be inefficient, causing reduced engine power.

In worst-case scenarios, the transmission is broken and must therefore be replaced, and a transmission replacement is not cheap by any means.

Clogged Catalytic Converter

Can You Drive Without A Catalytic Converter

The catalytic converter prevents bad chemical compounds from getting released into the environment.

In most cases, the catalytic converter gets clogged due to compounds that should not be there in the first place, such as excessive engine oil.

If it turns out that your catalytic converter is clogged, it will affect the engine by, for example, limiting the engine power.

Normally a catalytic converter does not get clogged unless another problem is hiding somewhere else. This may be anything from bad spark plugs to an oil leak.

That means that you should always get rid of the underlying problem before replacing a catalytic converter.

Vacuum Leak

Car Engine Vacuum Leak

A vacuum leak can mean many things, but in the automotive sphere, it is most commonly used to describe a leak in the intake manifold.

In other words, the intake manifold is not completely sealed, allowing air to enter the engine uncontrolled.

This may cause a variety of problems which vary by grade depending on how small or big the leak is.

A vacuum leak may cause many symptoms, including stalling, rough idle, and of course, reduced engine power.

Depending on the leak, it may be seen by the naked eye or a propane torch can be used to localize a hard-to-see leak.


There may be many causes for your engine to reduce its power. In many cases, the engine reduced the power electronically to protect it from potential damage.

Other times, the reduced engine power can be strictly physical, such as insufficient fuel reaching the combustion chamber due to a bad fuel pump or too little air because of a bad throttle body.

Whatever the case, this guide should help you get rid of the problem in a few steps.

If your car has more symptoms than just reduced engine power, or you suspect a particular part to be the culprit of the problem, make sure to check out our other articles about the relevant part.

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Bajro Muric

Bajro is an ASE-certified master technician and car enthusiast with a love for writing and teaching. He writes about anything regarding cars, from common problems and fixes to racing.