DPF, EGR and Carbon Build-Up
Petrol and Diesel
Book a Service
Book DPF Cleaning or a Carbon Check
Please allow a minimum of 2 business days. If you require a service sooner, please call us at 0800 522 734.
Carbon build-up affects both diesel and petrol engines. On a diesel it blocks the DPF (diesel particulate filter) and the EGR valve. On direct-injection petrol engines, including many VW, Audi and Skoda models, it coats the intake valves. The symptoms are often the same: warning lights, limp mode, rough running and higher fuel use.
We find the cause first, then talk you through the options, from DPF cleaning to replacement, so you can make the right call for your vehicle and your budget.
Why DPFs Block Up
A DPF traps soot from the exhaust. To stay clear it has to burn that soot off, which the engine does by itself when the vehicle is driven at a steady speed for long enough. The manufacturer sets when and how this happens.
The problem is vehicles that are never driven far enough. Short trips and town driving don’t give the burn-off time to finish, so soot builds up over months until the DPF light comes on, the engine goes into limp mode, or DPF cleaning is needed.
It’s frustrating, and many owners only find out at this point that their vehicle doesn’t suit the way they drive. We’ll explain what’s happening and what can be done about it, including whether a change in driving will keep the problem from coming back.
Signs of a DPF, EGR or Carbon Problem
- 01DPF warning lightThe filter is filling up and the burn-off hasn’t been able to finish
- 02Limp mode or loss of powerThe engine protects itself by cutting power
- 03Engine warning lightOften with DPF, EGR or sensor fault codes stored
- 04Black smokeA common sign of an EGR or injector problem on a diesel
- 05Rough idle or misfireOn direct-injection petrol engines, often carbon on the intake valves
- 06Higher fuel useFrequent burn-off attempts and carbon both cost fuel
- 07AdBlue warningSome vehicles count down to a no-restart if an AdBlue fault isn’t fixed
If your vehicle is in limp mode or the DPF light has come on, book it in soon. Driving on for long can make the blockage worse and the repair more expensive.
DPF Cleaning, Regeneration or Replacement
Which option is right depends on how blocked the filter is, its condition and the vehicle. We’ll go through them with you before anything is done.
We also look for the reason it blocked, such as a faulty sensor, EGR or injector, or the way the vehicle is used. Clearing the filter without fixing the cause means it blocks again.
EGR Valve and Cooler Problems
The EGR system sends some exhaust gas back into the engine to cut emissions. Over time soot builds up in the valve, the cooler and the intake, and the valve can stick open or shut.
Signs include rough running, loss of power, black smoke and fault codes. Depending on the build-up we clean the EGR by hand, send it out for cleaning, or replace the valve or cooler.
Carbon Build-Up in Petrol Engines
It isn’t only diesels. Direct-injection petrol engines spray fuel straight into the cylinder, so the fuel never washes over the intake valves. Carbon builds up on the valves instead, and we see it often on VW, Audi and Skoda engines.
Signs include a misfire, a rough idle, poor cold starting and a drop in performance. We confirm it with diagnosis and an inspection, then clean the valves by hand or send the work out to a specialist.
AdBlue (SCR) Faults
Many newer diesels use AdBlue to reduce emissions. Faults with the sensors, pump, heater or injector bring up warning lights, and some vehicles count down to a no-restart if the fault isn’t fixed.
We diagnose AdBlue faults properly and repair the cause, rather than just clearing the warning.
Helping Your DPF Stay Clear
Book a DPF or Carbon Check
Book online, or call and tell us your registration and what the vehicle is doing. Choose whichever workshop suits you.
Frequently Asked Questions
How much does DPF cleaning or repair cost?
It depends on the cause and the vehicle, so every job starts with a diagnostic scan ($132 incl GST) and testing. Once we know what’s wrong we give you an estimate before any work starts. Replacement can be expensive, so we always go through the options first.
Can you do DPF cleaning?
Yes. We can run a forced regeneration with diagnostic equipment, or remove the DPF and send it to a specialist cleaner, then refit it.
Why does my DPF keep blocking?
Usually because the vehicle isn’t driven far enough at a steady speed for the burn-off to finish. A faulty sensor, EGR or injector can also cause it. We check for both.
Is carbon build-up only a diesel problem?
No. Direct-injection petrol engines get carbon on the intake valves, and we see it often on VW, Audi and Skoda models.
Can I keep driving with the DPF light on?
Book it in soon. Driving on for a long time, especially in limp mode, can make the blockage worse and the fix more expensive.
Do you fix AdBlue faults?
Yes. We diagnose and repair AdBlue (SCR) faults at both workshops.
Our business is caring
Committed To Quality
“With two convenient West Auckland locations, Henderson and Avondale, KAAR is the place to go for Auckland vehicle repairs. Our fully equipped vehicle workshops and professional team of service technicians.”
Kelvin Armstrong
