Even though Mercedes had trouble making the first-ever Diesel Particulate Filter (DPF) on their 300D regenerate, they implemented an idea that is now a mainstay in modern diesel vehicles.
They’re now a must-have if you want your diesel engine to hit current emissions regulations.
Even though DPFs are now more effective and resilient than they were, they can be a severe problem if ignored, tampered with, or misused.
What Does a Diesel Particulate Filter Do?
Diesel Particulate Filters are a set of emission control gadgets that capture, store and dispose of exhaust soot.
Once the filter captures enough soot, it has to get rid of it and regenerate the DPF for further use.
The filter effectively reduces emissions, making your car compliant to emission regulations like Euro 5 exhaust emissions of 2009.
Signs that Your Diesel Particulate Filter is Blocked
Since the DPF is so important, most vehicles with a DPF have sensors to monitor how it’s performing.
A DPF Light Will Pop Out
If you have issues with your diesel particulate filter, an orange light with the outline of a muffler will appear on your dashboard.
Even though the light will vary depending on your vehicle’s manufacturer, it means:
- The diesel particulate filter is blocked
- The DPF efficiency is operating below efficiency
Your Car isn’t Punchier As Before
A blocked DPF increases back pressure in your exhaust system. Higher than usual backpressure will reduce engine efficiency.
It won’t matter how hard you accelerate. The engine won’t pull as hard as it does. While sluggishness might mean something else, it could always filter down to the DPF.
The clog saps energy from the engine as it struggles to push exhaust through the system living little for actual acceleration.
Your Gas Mileage is Terrible
Since your engine is working harder to push out those exhaust gases, you will naturally have to accelerate harder to compensate.
This translates to more fuel burnt for trips you would have cruised to easier if the engine was more efficient.
Your Engine Starts Harder
A blocked DPF adds backpressure to your engine. If the pressure builds up too much, the engine will have trouble starting up until you relieve that pressure.
Even if you can still get the engine to start, that pressure buildup could wreak havoc on your gaskets, the exhaust system, and piston rings. Have your DPF inspected as soon as possible to avoid more damage.
Turbo Problems
Since the blockage limits gas flow through the exhaust system, your turbocharger will be starved and won’t spin as fast as normal.
Apart from this, the exhaust temperatures build up, heating the turbocharger assembly above spec.
This will translate into oil leaks and reduced efficiency. If it goes on for long, the oil in the turbo system could carbonize, making the turbocharger run dry and ruin itself.
What Causes Blockages in Diesel Particulate Filters?
A couple of things will make your DPF clog and even die sooner than it should. The most common are:
Driving Short Distances at Low Speeds
The most common cause of DPF blockages is driving short trips at low speeds. Diesel engines thrive out in the open roads at cruising speeds.
The short town runs with a lot of traffic jams tarnish fuel efficiency and deny the DPF a chance to self regenerate by burning off all that trapped soot.
Skipping Maintenance Schedules
Servicing your engine on time is a great way to keep it working efficiently and avoid unnecessary emissions.
This reduces how much-uncombusted fuel, burnt oil, or coolant you send through the exhaust system.
The DPF works perfectly when filtering fuel exhaust but will falter once there is some oil or coolant in the exhaust.
That is why you should be worried as soon as your vehicle shows signs of burning oil or coolant at an alarming rate.
Low-Quality Contaminated Diesel
Even though low-quality diesel is uncommon since authorities strictly regulate diesel quality, using adulterated or contaminated fuel will harm your DPF.
The DPF design doesn’t account for the extra impurities that will end up in the filter and can’t burn off during the self-regeneration cycle.
ProTip: Aftermarket modifications that alter air/fuel mix or increase engine exhaust could also cause a DPF blockage if they lead to an exhaust flow rate higher than what the stock DPF can handle
How to Take Care of Your DPF
Taking good care of your DPF is simple and perhaps uninvolving. All you have to do is use your diesel vehicle for longer highway cruises.
Avoid diesels if you most do in town commutes. You will not give it the time it needs to regenerate.
If you find yourself stuck in short town commutes for a while, you will have to take it through a regeneration cycle before or immediately after the DPF light pops up.
How to Passively Regenerate a DPF
Passive regeneration will happen when you drive at motorway speeds on a long journey of around 40 to 60 minutes.
At such high speeds, the exhaust temperature will rise to a considerable level that is enough to burn off excess soot in the filter.
You won’t have to worry about this if you do such a commute or drive at least twice a week.
If you don’t and the DPF is blocked too much, you will have to remove the soot actively.
Actively Regenerating Your Diesel Particulate Filter
Most diesel vehicles with a DPF fitted offer an active regeneration mode that alters how the ECU controls the engine to achieve better regeneration.
The computer will inject more fuel to help increase exhaust temperatures faster and burn the stored soot more efficiently.
You still have to drive for over 30 minutes at a speed higher than 40 mph to run a complete regeneration cycle.
Luckily, most engines will turn off the DPF warning light as soon as enough soot has burnt off and the filter operates within acceptable limits.
Active regeneration has notable side effects like:
- An acrid smell from the exhaust
- Deactivated stop/start technology
- A change in the engine sound
- A slightly higher idling speed (you shouldn’t be idling anyway)
- A notable increase in fuel consumption
What to Do if Passive or Active DPF Regeneration Fails
If the normal regeneration cycle doesn’t work, chances are you will get additional DPF warnings, or the single warning light will turn red.
If this happens, you need to take your vehicle for servicing as soon as possible to avoid further damage.
Servicing can range from forced regeneration to replacing a completely failed diesel particulate filter.
Forced regeneration involved removing the filter and washing it to get rid of the soot. Even though it’s not 100% guaranteed that such cleaning would work, it is cheaper than a replacement and worth the effort at times.
Can I Get Rid of the Diesel Particulate Filter?
While you can physically get rid of the DPF, such a modification could render your vehicle unroadworthy or even be illegal in your region.
Known as a DPF delete, it involves removing or bypassing the DPF and configuring the engine computer to work without the filter.
You won’t get the DPF light ever again, and your engine might even generate some extra horsepower, torque and give better gas mileage, just as is the case with getting rid of a catalytic converter.
Will My Vehicle Pass Emissions Without a DPF?
A DPF check is part of emissions tests like the MOT test from 2014. If you do a DPF delete, your vehicle will fail the emissions test.
Apart from failing due to the warning light popping up on the dash (if your DPF delete kit doesn’t suppress this), emission sensors will detect higher than normal gases in your exhaust; hence the emissions test fails.
How Often Does a Diesel Particulate Filter Need Changing?
You can easily get 124,000 miles (200,00 kilometers) from your DPF if you take good care of it. This means servicing your engine on time, avoiding oil leakages, and driving at highways speeds for longer.
The DPF will block and even be ruined beyond repair sooner if you stick to short slow city commutes, don’t service your engine, or suffer from an unexpected in-engine oil leak.
How Does My Car Computer Tell How Much Soot is in the DPF?
Your ECU uses pressure sensors to determine the pressure difference between exhaust going into the DPF and that coming out of it.
The difference can then be translated to fill percentages. The ECU will either use them to activate automated regeneration or pop up a warning when it’s time to do something about the blockage.
Can I Clean a DPF Myself?
Yes, you can. The easiest way to clean it is by using additives in your diesel fuel that lower soot’s burning temperature, making it easier to burn it off.
This is a perfect solution that you should try now and then before your DPF clogs in the first place.
If it is already clogged and cannot regenerate in place, you will have to go through the messy forced regeneration cleaning.
Taking off exhaust components is hard since bolts tend to be stuck in place. It would be wise to hire someone for the clean unless you are very ‘car handy’ and have a way to dispose of the ensuing dirt.
Does AdBlue Stop DPF Problems?
AdBlue is a commercial product designed to destroy NOX (nitrogen oxide) in your exhaust. You will find a cap to the AdBlue tank next to your fuel tank door or at another point if your vehicle is Euro 6 emissions compliant.
The chemical is a mixture of urea and demineralized water at different compositions depending on your engine type.
Apart from destroying NOX, it will also make it easier for the DPF to burn exhaust particles at temperatures as low as 190 Celcius instead of 450 degrees Celsius by activating a chemical reaction.
If your vehicle has a DPF tank, it will be more forgiving, and you can use it for slow-moving short trips more than one without. Just remember to top up the tank as soon as it’s empty to keep enjoying the benefits and keep that annoying warning light away.
Can You Drive With a Blocked DPF?
While you could keep on driving with a blocked DPF, it is not wise to do it for longer than necessary.
If the light pops up or you suspect a blockage, take your vehicle on a long highway cruise at speeds above 40 mph to trigger a passive or even active regeneration. The light should go away if everything is fine.
Avoid short slow trips as much as possible until you do something about the warning.
If the regeneration cycle fails, you will have to try cleaning the DPF in forced regeneration or buy a replacement.
Is Idling Bad for a DPF
Your diesel engine will produce particles in its emissions even at idle. The problem is idling won’t have enough heat to burn them off.
This means you will be gathering excessive soot apart from burning more fuel and ruining your overall MPG.
Nowadays, idling diesels isn’t necessary. The fuel additives are better, and diesel doesn’t gel as much as it used to back when idling was a good idea.
Moreover, modern engines have thermostats that regulate coolant flow in the cold engine, making it easier for an engine to come up to operating temperatures within a minute or two.
You can warm up your engine by starting the drive slow and waiting until it’s within average operating temperature before picking up speed.
That is why even diesel engines of the modern error have start-stop systems to help get better gas mileage.
Switch off your diesel engine when leaving or stopping at a parking spot for more than five minutes.