Car Losing Power: Why does the engine lose power over time?

Výfukový systém v aute
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Loss of power over time is inevitable for every single internal combustion engine. But what is the cause, and how to prevent these problems in the first place?

We have prepared an article to answer this question - we will look at the possible causes of the loss of performance and how they can be eliminated.


Why is my car losing power?

A malfunction of some engine components can cause a sudden loss of power. If the defect is removed, the engine performance will be back, and you can continue driving with peace of mind.

However, this article will focus on the gradual loss of horsepower, usually caused by irregular or insufficient maintenance or wear of some engine components. There is no way to determine how much power the engine will lose in a certain time, but one rule applies - the better you care for the engine, the smaller the power loss will be.

The engine is like a living organism and needs four things to function properly: fuel, air, compression, and spark (gasoline) or ignition of the mixture (diesel). If any of these things are not optimal, the engine loses power. So let's take a closer look at the causes of performance loss.

1. Air filter

To function properly, every internal combustion engine must draw a certain amount of air into the cylinders. However, if less air enters the cylinders than necessary, it will cause a reduction in engine performance. A clogged air filter can cause this problem.

Športový filter

Fixing this problem is straightforward and cheap, so you should not wait to replace the air filter. Changing the air filter once a year or approximately every 8 to 15 thousand miles (10 to 20 thousand kilometers) is recommended, depending on the dustiness of the environment in which you drive.

However, the loss of power may not be caused only by a clogged air filter but also by clogged and carbonized intake ducts or other similar problems.

2. Spark plugs

Improper and, thus, insufficient ignition of the mixture can be another cause of your car losing power. It is necessary to check the condition of the spark plugs. The spark plug electrodes wear out over time and can be clogged with various deposits.

Zapaľovacie sviečky

These impurities can be removed, but since spark plugs are not expensive parts, it is recommended to replace them. The lifespan of a normal spark plug varies between 30 to 50 thousand miles (45 to 80 thousand kilometers), so you should not forget to replace them regularly.

If the spark plug works only partially or does not work at all, car jerking or irregular operation of the engine occurs. This is because the engine works on fewer cylinders, which reduces the engine power and leads to other issues.

3. Exhaust system

What goes in must go out. An exhaust system is used to remove exhaust gases from the cylinders, but it also requires some maintenance. The most common exhaust system problems that cause a loss of power include a damaged, clogged catalyst or muffler or a leaky exhaust pipe.

Výfukový systém v aute

There are only two ways to solve the problem of a leaking exhaust pipe. Either by welding the cracks or replacing the damaged part of the exhaust pipe. This problem is extremely easy to identify and cannot be overlooked since your car's noise is way above what it should be.

However, problems with the catalytic converter and muffler may not draw attention to themselves so quickly.

The catalytic converter suffers, especially if you mainly use your car for short drives, during which the engine does not have time to warm up. It means that it burns a rich mixture repeatedly, which is not something a catalytic converter likes. It also suffers when your car burns too much engine oil due to damage or wear of a certain component.

In such a case, there is a risk of the catalytic converter becoming clogged with dirt, which will cause reduced exhaust pipe permeability and, thus, a reduction in engine performance. A clogged catalytic converter can be cleaned using various special cleaning agents, but it must be replaced if it is too clogged, which is not the cheapest solution. In addition to clogging, however, the catalytic converter can be damaged mechanically, most often if unburnt fuel is burning.

A damaged catalytic converter will cause false reports from the lambda probe, based on which the engine control unit will not be able to determine the correct ratio of fuel and air in the working space. The muffler can suffer from similar problems as the catalytic converter.

The muffler can become clogged, which will cause poor passage of exhaust gases, but it can also corrode from the inside and fall apart, leading to other problems and, of course, a reduction in engine performance.

4. Fuel system

Oil and fuel filter

This mainly concerns the fuel pump, injection device, and fuel filter. If the required amount of fuel is not getting into the cylinder, it is probably clear to everyone that it results in the car losing power. The fuel pump is usually located in the fuel tank.

The fuel pump can wear out over time, causing it to struggle to deliver enough fuel, especially at higher revs or heavy engine loads. However, a clogged fuel filter may be a direct cause, which, if it is clogged, will not let in enough fuel. The decrease in performance is again most noticeable at higher revolutions or greater engine load.

Replacing the fuel filter is straightforward and cheap, contrary to fuel pump replacement, which is far more expensive. In addition to the problem with a worn fuel pump and a clogged fuel filter, there may also be a problem with the fuel injectors, which tend to become clogged with dirt due to low-quality fuel.

Similar to the previous two problems, the drop in performance is noticeable only at higher revolutions or with a greater load on the engine. However, solving the problem with the fuel injectors is more difficult than solving the previous problems combined. There are only two options - an expensive repair or an even more expensive replacement of the fuel injectors.

5. Throttle valve

The throttle valve might be controlled mechanically by using the cable. This cable can loosen over time. Therefore, it is necessary to tighten it again so that the connection between the accelerator pedal and the throttle body is as tight as possible.

The loose throttle valve cable will cause the valve not to open when the accelerator pedal is slightly pressed. When fully pressed, the valve will not be fully open, making it impossible to squeeze maximum power from the engine.

Throttle body

Even the throttle body itself is not a maintenance-free device, so it is advisable to regularly clean it of various impurities and deposits with special cleaning agents.

6. Loss of compression

Loss of compression is a serious problem that can be solved, but it would not be cheap. Leaks in the combustion chamber cause loss of compression.

Leaks in the combustion chamber can be caused by the following:

  • Worn or damaged piston ring

  • Worn engine cylinder

  • Damaged cylinder head

  • Damaged gasket under the cylinder head

  • Damaged valve

  • Damaged valve spring

All these problems cause the combustion chamber to leak, which leads to the extrusion of the mixture during compression and the subsequent reduction in engine power. Pushing out the mixture reduces the pressure in the combustion chamber, which would otherwise act on the pistons. It should also be added that fixing these problems is laborious and expensive.


In conclusion, I would like to add that some of the causes of performance loss can be removed easily and cheaply. Still, others require a dose of professional experience and a significant financial injection. If you don't take care of your car regularly, the horses under the hood will run away sooner or later.