Home Tips Particle Filter How to Fix Breakdowns

One of the recurring problems in today’s cars is the particle filter. It is a solution designed to make combustion cars cleaner, but also an important source of headaches since their repair or replacement have a high cost.

Knowing this system will help you understand how it works and also prevent its problems, but avoid them completely. With a few simple guidelines you can adapt your driving to the existence of the particle filter and save a good money on maintenance, since it is one of the most recurring breakdowns … and expensive.

How the particle filter works
The particle filter (also called FAP or DPF – short for Diesel Particle Filter) is a device that is located in the exhaust pipe. Its mission is to retain solid particles generated by engines that come out together with gases, to lower the level of polluting gases. When full, it incinerates them, in a process called regeneration.

An emission control system is made up of different parts:

A lambda probe: This is a sensor that measures the oxygen concentration, to check the quality of a combustion and that sends the data to the control unit.
A catalyst: it makes the emitted gases less polluting, thanks to a chemical reaction (catalysis, hence its name) that occurs with the catalyst materials from which it is manufactured.

The particulate filter itself, basically made up of a “grid” structure.

Differential pressure control sensor: measures the pressure of gases between two points
Temperature probe: a device that transmits the temperature of the emitter

The particulate filter retains solid particles, allowing gases to escape through its walls. It is the differential pressure sensor that indicates to the control unit that a high level of retained particles has been reached, which could cause the filter to clog. The time for regeneration has come.

Regeneration of the particulate filter
In the process of regenerating the particulate filter, the temperature of the exhaust gases increases until reaching around 600 degrees, which is the combustion temperature of carbon, which turns into gas and thus the filter is emptied.

The regeneration process, which the car performs every 500 – 1,000 km (the figure varies greatly depending on the driving done), does not completely eliminate the porous walls of the filter, there is always some residue. You have to drive around half an hour above 2,500 rpm to carry out the process correctly.

When regeneration is taking place the car usually warns. Also more fuel is consumed during it (around 15% more), since with a mixture with less air the temperature increases. It is normal.

It is important not to turn off the engine during the process. If it happens once nothing will happen, but if it is repeated several times it is then when you will have to go to the workshop to carry out the regeneration. And you better go if the dashboard warning light comes on: because if the filter breaks, the bill will be much higher.

What cars have a particle filter?
It was in 2009 when the Euro 5 standard came into force, which mainly aimed at reducing the impurities of the particles emitted by diesel cars. Any car with this fuel of less than 10 years old has this system, as the manufacturers

Newer is the incorporation of particulate filters in gasoline cars. Although we can say that the combustion in a gasoline engine is “cleaner” beyond that they emit more CO2, it is also true that modern direct injection gasoline engines generate many microscopic and carcinogenic particles.

It was not until 2017 that the permitted particulate emissions from diesel and gasoline cars were equalized. Although the Euro 6 regulation had already begun to control the number of particles in the total mass of emissions, it was not until the entry into force of the Euro 6c regulation that gasoline cars began to have this device in a massive way. And beware, they are effective because Volkswagen ensured that particle emissions are reduced by up to 90% compared to engines without filters.

Types of particle filters
In today’s cars there are mainly two types of FAP:

Filter without additives: The most common, used by most manufacturers. The engine is placed closer since the gases that come out from there are at a higher temperature and facilitates the combustion of the particles during regeneration.

Filter with additive: It is further from the engine and to reach the ideal temperature it is necessary to add a liquid to the diesel (not to gasoline). It is not Adblue (which is the additive that the catalyst uses to reduce Nox – nitrogen oxides -), but it has a separate tank and lasts about 100,000 km. After the period indicated by the manufacturer, it must be filled in (it costs around 100 euros).

Particulate filter problems
Although the regeneration of the particulate filter has been carried out strictly and without incident, over the course of kilometers it accumulates solid particles from the combustion smoke that begin to obstruct it.

It is then that the engine failure warning light will come on and the car will lose power significantly. Then it is time to replace the filter (with a significant economic cost). A complete, non-original particulate filter costs from about 400 euros to 900, depending on the model. An original spare part has a price of approximately 800 euros to 1,500 euros

You can also proceed with cleaning, which in most cases gives good results.

Cleaning the particulate filter
Depending on your vehicle, your trusted workshop will recommend that you clean the filter with some of these processes. Its cost ranges between 100 and 200 euros:

Cleaning liquid: The filter is disassembled and, after covering all the holes, they inject a liquid similar to a decarbonizer. It is a slow process, since it has to go through the grids, which are also obstructed. It is then left for about 12 hours before being washed with pressurized water. Then you have to assemble it as soon as possible and drive with the car so that the hot gases dry the filter well and it can return to normal operation.
Ultrasound: After disassembling it, the particle filter is immersed in an ultrasonic washer. Through vibrations, the soot and sediment remains are released. When the process ends, it is also washed with pressurized water.
Chemical additives: There are special liquids to clean it, but they are not very effective if the obstruction is very large.

In the workshop it is also possible to force the regeneration to eliminate these residues. It is a process for which it is necessary to connect the vehicle to a diagnostic machine, so that the temperature of the engine increases and with it the temperature of the gases given off from the exhaust pipe.

Through the heat produced inside the exhaust pipe, the soot particles are burned and the filter is clean. They must be done by professionals in a controlled environment. And it is that, during the process, the temperature of the gases increases and also the emission of polluting gases, in addition to being able to cause a fire.

Care of the particulate filter
The life of an anti-particle filter depends on many factors. The main one is the use that is given to the vehicle, especially if it is a diesel engine. When only short trips are made, such as those made in the city, the exhaust gases do not reach the appropriate temperature and the regeneration is not carried out correctly … or even the process is interrupted.

So a diesel is not a good idea to always drive in the city. Going at low revs constantly can be a cheap headache, ultimately spending more money than you thought you could save by betting on that fuel:

To avoid this, you must comply with five maxims:

Rajatable maintenance: Follow the maintenance plan indicated by the manufacturer in your car manual.
Choose a good lubricant: Models with a particle filter usually use a Low Saps oil, (low in ash, phosphorous and sulfur). This oil is capable of withstanding the “dirt” that occurs when more fuel is injected than necessary during the regeneration. Although it costs something more, it is worth it.
Do not stop the engine during regeneration: There are models with a warning light that informs of the process. If not, pay attention to whether the engine “snores” and / or increases instantaneous fuel consumption.
Avoid short trips: The engine does not reach the ideal temperature … and the filter does not. In addition, more solid particles accumulate on these paths. From time to time the engine will have to go through a regeneration cycle and will not be able to do it properly.
Road trips: Driving on the motorway at least 30 minutes every 1,000 km, at around 2,500 rpm, ensures correct regeneration of the particulate filter. If you ever detect a loss of power, the filter may start to plug. Go out on the road for a while so that the car reaches temperature.
In no case:

Cancel the particulate filter: The car works the same, but it is illegal and would not pass the ITV.
ECU reprogramming: This measure aims to ensure that the regeneration is carried out more in accordance with the type and driving habits of the car owner. But it is not effective in all cases and may lose the warranty of the car or affect, if not done well, the operation of the engine.