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Why does my car lose power?

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WhoCanFixMyCar explains why your car might be losing power and what you can do to fix it.

Most drivers know their cars inside out, which means they can tell straight away when the engine isn’t giving them as much power as it usually would. A loss of power will be most apparent during acceleration, but even when you’re driving at a constant speed you may notice your car flagging. 

If this is the case, we know how eager you’ll be to get your car working normally again, so we’ve created this guide to help you diagnose what might be going wrong. 

Guide Contents:

Clogged Fuel Filter

Clogged Catalytic Converter

Clogged Air Filter

ECU Error

Faulty Fuel Injectors

Worn Spark Plugs

MAF Sensor Malfunction


Clogged Fuel Filter

The fuel filter plays an important role in making sure that the right quantity of fuel, which is free from dirt particles, reaches the engine chamber. Sometimes, the fuel filter becomes clogged with debris, and when this happens the engine can’t perform at its optimum level. As such, when you put your foot down more fuel will be sent to the filter but not as much will be able to get through, resulting in a loss of power.

Fortunately, getting your fuel filter changed is relatively cheap.


Clogged Catalytic Converter

Catalytic converters control the emissions that leave your exhaust. They contain aluminium or ceramic honeycomb mesh coated with platinum and palladium, both of which chemically react with carbon monoxide and unburnt fuel. This redox reaction results in the creation of carbon dioxide and water, two much less harmful bi-products. 

When catalytic converters become clogged, the first sign is usually a loss of power and acceleration. Eventually, this can lead to engine failure if left untreated, so it’s best to book in with a local garage as soon as possible.


Clogged Air Filter

Air and fuel are combined within your car’s combustion engine to generate the power required for movement. Before it enters the chamber, the air must first be filtered to make sure it is free from debris and impurities which might otherwise cause severe damage. 

As you might expect, air filters tend to get clogged when they have been used for a while, which ultimately means that the amount of air getting into the combustion chamber is limited. Consequently, the engine will struggle to generate enough power to run the car.

Getting your air filter replaced shouldn’t cost you too much, and as soon as it’s done your car will be back up to full power.


ECU Error

Cars that have an ECU (engine control unit) can sometimes lose power if the system detects a mechanical error in the car that doesn’t actually exist. As a result, the ECU tells the car to lose power, or in some cases stop completely, to prevent an accident. 

ECU errors like this will usually go away on their own, but you should still take your car to be checked by a professional to make sure that it doesn’t happen again.


Faulty Fuel Injectors

Fuel injectors are responsible for introducing fuel into the combustion chamber. This happens at extremely high-pressure, and the amount of fuel must be precise for combustion to occur successfully. Even a slight miscalculation will disrupt the process, resulting in a loss of power. In the worst case scenario, your cams and pistons may break as a result, which will make the repair bill significantly more costly.


Worn Spark Plugs

If you find that your car feels particularly unresponsive when you put your foot down on the gas, this could be due to worn spark plugs. 

Like any car part, spark plugs depreciate over time, and when this happens they have a harder time creating the spark that powers your engine. As a result, you may experience a loss of power, decreased performance, rattling or knock-like noises and poor fuel economy. 

Spark plugs themselves are relatively cheap, and with a little mechanical know-how and patience it’s possible to change them yourself. However, since they play such an important role in the overall functioning of your engine, you might want to have them fitted by a mechanic.


MAF Sensor Malfunction

The MAF (mass air flow) sensor measures the amount of air required for the car to accelerate. It then sends this measurement to the engine control unit, which makes the throttle open as necessary.

However, if the MAF sensor is faulty it will likely result in a loss of power. Heat and dust can both cause sensors to malfunction, so cleaning them frequently can help to prevent this problem in the future.


It can be a frustrating experience when your car isn't operating at full power, but the good news is that WhoCanFixMyCar can help you find reliable local car repairs that won't break the bank.

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