DPF (diesel particulate filter) faults and issues

As with so many aspects of modern life, whilst technology brings welcome advances, it also tends to bring its own problems. This is never more true than when it concerns vehicle technology. Diesel-powered cars and light commercial vehicles have become increasingly popular over recent years, primarily because of their comparatively low running costs and ability to achieve high mileages with relatively good reliability. Once thought of as slow, noisy and uncomfortable, standards have improved so much that today's diesel vehicles are little different from their petrol-powered counterparts, and in some cases actually better. Technology has contributed massively to this and modern electronic engine management systems ensure a good combination of economy and performance from diesel engines. The polluting diesel vehicles of yesterday have been replaced with comparatively clean-running, modern machines that offer remarkable efficiency and remarkably low levels of exhaust emissions.

exhaust componentsHowever, there are some issues with modern diesel cars and the most notable of these is the DPF. Standing for diesel particulate filter, DPF systems have become increasingly common on diesel cars since early this century. They are now fitted as standard by many manufacturers in most countries in order to provide a cost-effective method of meeting exhaust emissions standards. However, many query the virtue and efficiency of this solution. Basically, and as the name suggests, the at the heart of the system is a relatively simple physical filter, designed to remove particles from the vehicle's exhaust, in the case of diesel this is mainly carbon in the form of soot. The issue that causes problems is that the filter can actually cause some back pressure in the exhaust system, adversely affecting efficiency, and in turn adversely affecting economy and performance. To prevent blockage, on the vast majority of cars it is also essential to quite frequently heat the exhaust significantly above normal temperature, which is accomplished by a reasonably lengthy drive at motorway speeds. Known as 'regeneration', this process heats the DPF unit to the extent that the carbon collected in it mostly burns off. Somewhat ironically, this naturally increases overall emissions, particularly carbon dioxide, which is produced as the carbon burns away. There is also some debate as to the effectiveness of the filters in the first place, as modern diesel engines with efficient and correctly calibrated management systems are easily able to perform well within European emissions standards.

In view of the potential problems and costs, why do manufacturers fit diesel particulate filters in the first place? The answer is simply for financial reasons resulting from economy of scale. Fitting a DPF means that engine management systems do not need to be individually set to very fine tolerances, and that accordingly, vehicles can be sold across a wide range of markets with vastly differing fuel quality, but without the need for fine tuning. Bought in massive quantities, DPF units are low enough cost to manufacturers to make their fitment far and away the most economical way of meeting emissions targets across a wide range of vehicles and sales markets.

In practical terms for car owners, DPF systems can prove a nightmare. Under some circumstances they can have a limited life span. Worse, if a car is used mainly for short journeys and or town driving, the filter can become blocked in a surprisingly short space of time. If this happens and regeneration is not carried out quickly, the unit can become seriously blocked and major engine damage can result. Even if only partly blocked, a DPF can notably reduce performance and adversely affect fuel consumption. Every diesel driver's nightmare is to see the 'DPF warning' light remain illuminated on the dashboard. A nightmare that is made worse by the sort of prices quoted by dealers to replace the unit, which can be literally thousands of pounds in many cases. However, we can offer solutions to this increasingly common problem. First, our equipment allows us to correctly diagnose any DPF problems, which may not always actually be down to the unit itself. If it does turn out that there is a problem with the DPF, we can offer proper regeneration and if necessary, can send the unit away to be professionally cleaned, bringing it back to 'as new' condition at a faction of the cost of replacement.

At MK T and B Centre, we have the correct equipment and training to diagnose and repair DPF systems properly, and reprogram your vehicle's engine management computer. Please contact us for a quotation or if you require further information. Please note, we are aware that a number of companies are still offering DPF removal services. Under no circumstances should you consider this. Changes to legislation in 2014 mean that if your vehicle was fitted with a DPF when new, it must be present and correctly functioning in order for the car to pass its MOT test.

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