Car Losing Power: Possible Causes and Culprits

Over the years, sitting behind the wheel of your car, you become accustomed to the way it works and its capabilities. It’s no surprise therefore, that you’ll quickly notice when your vehicle lacks the same oomph as you usually experience. A loss of power is most apparent when you’re accelerating, and can be due to a number of reasons including air flow into the engine, fuel flow and even faults with the exhaust system. So, if your vehicle is consistently putting in a sub-par performance, these could be some of the reasons why…

Why is my Car Losing Power?

Fuel system

If your car is not getting the required flow of fuel, then this will usually result in a drop in power. Some of the most common causes of fuel problems include:

Clogged fuel filter

The fuel filter is designed to prevent dirt and debris from entering the fuel system. However, over time this can itself become clogged with all the excess material in the fuel system, impeding the flow of petrol or diesel into the engine. Such a problem with the filter, will often show up when you are driving up a hill or trying to overtake a car – as you will not be able to achieve the power and acceleration you need to achieve.

Fuel injectors

Fuel injectors can also become clogged with dirt over time, which prevents the proper flow of fuel into the engine. You’ll most likely notice this problem when accelerating, as your vehicle will struggle to reach high revs. It may also be accompanied by ignition, stalling and misfiring problems, and you may even become aware of the smell of fuel around your car.

Diesel particulate filter

The diesel particulate filter (or DPF) can easily become blocked with particles. Many cars have systems where you can burn off the debris and particulate stuck in the filter at high speeds, but if you are only ever getting out into the gridlocked urban crawl this may not happen. Some cars even have a system where the DPF will switch the car into a limp home mode. If this happens to you, then get to your local garage as soon as possible, to have the part cleaned.

Exhaust system

Your engine needs to clear out old exhaust gasses in order to take in clean air for combustion. If your exhaust system is not working properly, this will in effect choke your engine and stop it from reaching full power. Some of the causes behind this could be:

Backfiring exhaust

No one wants to have a backfiring exhaust. Usually the problem is caused by a poor air/fuel mix that causes the unburned fuel in the exhaust fumes to explode when it comes into contact with the hot metal exhaust. These small explosions will cause you to lose power under acceleration. However, the cause of this issue will generally be somewhere in the fuel system – such as the fuel pump or the carburettor.

Blocked catalytic convertor

Over time your catalytic convertor’s effectiveness at filtering exhaust gasses may diminish. This can lead to the part becoming clogged, making it difficult for the exhaust gasses to pass through the intricate mesh of honeycombed precious metals that cleans out the harmful particles. Such a blockage will cause the exhaust gasses to become backed up in the engine.

Clogged exhaust

The whole exhaust system is not immune from blockages. Old leaves, bits of grit and gravel or even rubbish papers and plastics, can get lodged in your exhaust and stop it from functioning properly. If you’re experiencing a loss in power, then this is quite an easy one to strike off your list.

Engine

As the main driving force behind your vehicle’s power, some possible causes of a loss in power could be the following issues in the engine:

Turbocharger

The turbo forces air into the engine at higher revs, giving it the extra oxygen it needs for increased combustion. Turbochargers can suffer from issues if there is a hole or lose connection in the tubing, which will impact performance. Similarly, it can get blocked up with leaves, rubbish and grit and needs to be cleared regularly. Finally, the turbocharger is highly dependent on oil, so make sure that all your oil systems and filters are working properly.

Timing belt

If your timing belt does not have the correct tension, or has been poorly maintained, this can cause your engine valves to open and close at incorrect intervals, resulting in poor engine performance. This problem is one of the rarer ones on our list, and is accompanied by a tell-tale rattling coming from the engine.

Poor compression

Holes, leaks in valves, problems with the head gasket and other engine issues can cause a loss of pressure (poor compression) within the engine, which means you will not be able to achieve full power and performance.

Bad air filter

The air filter is designed to catch small pieces of grit, dirt, rubbish and debris that would negatively impact the performance of the engine, if they were to penetrate the combustion chambers on your vehicle. Over time however, the filter itself can become blocked, preventing the engine from getting the oxygen it needs to run properly. Check the part for blockages and free up your engine.

Electrical systems

Failures in electrical systems can stop the engine from operating at full performance. Some of the issues that may reduce power include the following:

Engine warning light is illuminated

Not only does the engine warning light point to a problem within your engine, it may also put your car into a kind of reduced power mode (known as a limp mode) where it operates at lower levels of performance, to ensure the driver is safe and the chances of getting into an accident are reduced.

Spark plugs are failing

Your spark plugs individually ignite the fuel in the chamber of their respective pistons. If one or more these stop working, this will cause unburnt fuel to pass through the engine, creating misfires. Plugs get worn out eventually, and have a lifespan of around 80K to 100K miles.

Ignition coil problems

And as we mentioned, the ignition coil powers the spark plugs. If this part is faulty, then you’ll notice problems when out on the road, with misfires, poor idling and a reduction in fuel efficiency. Eventually if you overlook ignition coil problems, your car will fail to start, leaving you with a tow bill in addition to a repair bill.

Camshaft position sensor error

Most cars use an electronic control module (ECM), that factors in the camshaft speed to calculate timings for the fuel injection and ignition systems. If there is a malfunction with this sensor and incorrect information is sent to the ECM, then this can result in poor performance or may even stop the engine altogether.

MAF error

The mass airflow sensor is another sensor that provides information to the ECM. In this case it provides a variable used in the calculation on engine load and thus performance. Any failure in the part would diminish the engine’s power output.

Oxygen sensor error

Gasses exiting the vehicle are monitored with the oxygen sensor, positioned in the exhaust system, which sends information back to the ECM about the air-fuel mix being used by the car. This in turn controls the fuel injection and engine timing systems – any problem with these will impact power and performance.

Cooling system

Cars generate a huge amount of heat. This needs to be controlled and dissipated by cooling systems within the vehicle. Problems with cooling can show up in the following way:

Overheating cooling system

Expect a reduction in performance in high ambient temperatures as your car’s cooling system has to work that bit harder. If you are experiencing problems with heating in cool temperatures, then this will lead to a loss of performance. It is also one of the biggest red flags, indicating serious engine problems and deserves the attention of a professional.

A last word

Other potential causes of power loss include issues with the EGR valve and the injection pump delivery value (on diesel engines). Loss of power is a serious issue, and could lead to accidents if you expect a certain level of acceleration from your car in a tight situation. Always drive with due caution and get your car checked out if there’s any drop in performance.