Why Does My Car Lose Power?

Ellie Dyer-Brown, 3 months ago

3 min read

  • Advice
  • Maintenance
  • why
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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, meaning they can tell immediately 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 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 a vital role in ensuring that the correct quantity of fuel, free from dirt particles, reaches the engine chamber. Sometimes, the fuel filter becomes clogged with debris; when this happens, the engine can’t perform at its optimum level. 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.

A mechanic removing the fuel filter from a car.

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, 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 by-products. 

Catalytic converter being removed from old vehicle.

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

Before air enters the combustion chamber, it must be filtered to ensure it is free from debris and impurities that might otherwise cause severe damage.

As you might expect, air filters tend to get clogged when used for a while, which ultimately means 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 - around £60 - 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 repair

ECU errors like this may 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.

The average price of an ECU repair booked through WhoCanFixMyCar is £154.23.

Faulty Fuel Injectors

Fuel injectors are responsible for introducing fuel into the combustion chamber. This process 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, making the repair bill significantly more costly. 

Fuel injection replacement

Worn Spark Plugs

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

Spark plugs

Like any car part, spark plugs depreciate over time; 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 are relatively cheap, and with some mechanical know-how, it’s possible to change them yourself. However, since they play such an essential 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 air the car requires to accelerate. It then sends this measurement to the engine control unit, which makes the throttle open as necessary.

Close up of a mass air flow sensor.

However, if the MAF sensor is faulty, it will likely result in a loss of power.


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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