DPF and engine lights on, and no power?
If the car suddenly loses power with the engine and DPF lights on, it may have gone into limp mode. Ease off, get off the motorway or main road somewhere safe, and switch off. If you can smell exhaust fumes inside the car, open the windows and stop as soon as it's safe. Don't drive far until a mechanic has looked at it.
Why Sydney diesels block their filters
RACQ says low-speed and stop-start driving is the most common cause of DPF problems, because it stops the filter's clean-out, called regeneration, from starting or finishing. An active regeneration typically needs five to 25 minutes at about 80 km/h or more.
That's hard to come by in a city whose traffic runs at capacity. Sydney has 160 kilometres of motorways, freeways and tolled roads, and a regular run on them is what a city diesel needs: RAA suggests 20 to 30 minutes at highway speed each week. The tolls are part of owning a diesel here.
Exhaust rules that matter in NSW
Smoke gets reported
In NSW anyone can report a vehicle they've seen smoking for more than 10 seconds continuously. The EPA matches it to the rego and writes to the owner, recommending the car be checked. On a cold morning condensation can look like white smoke, so a little steam at start-up isn't the same thing.
Noise limits
The NSW EPA sets a stationary noise limit of 90 decibels for a car built after 1982. Temporary fixes such as steel wool, or valves and baffles that aren't welded or riveted in place, are prohibited. A defective vehicle notice can lead to suspended rego, and you can take the car to a mechanic of your choice for the repair.
The right trade for the job
NSW has an exhaust repair class of tradesperson certificate for fabricating and repairing exhausts, and an underbody class covering exhausts, brakes and suspension. For a welded pipe or a new muffler, ask which one the person doing it holds.
Cleaning, a forced regeneration or a new filter?
Once a filter is badly blocked, RACQ says it needs a forced regeneration, which may also mean an oil and filter change because fuel can end up in the oil. Beyond that, the filter may need cleaning or, as a last resort, replacing, which RACQ calls very expensive.
Whichever it is, the mechanic should find out why it blocked, whether that's the driving or a fault elsewhere in the engine. If nothing changes, it'll block again. And we wouldn't let anyone talk you into removing it: it's part of the car's emissions equipment.
What a good written estimate shows
- What the mechanic found, and why they think the filter blocked.
- Whether it's a forced regeneration, a clean or a replacement.
- Whether the engine oil needs changing because fuel has diluted it.
- Parts and labour shown separately, and when the car will be ready.
- The warranty on the work, written on the invoice.
What we'd do
We'd have the cause found before paying for any cleaning. If it's a diesel that rarely leaves the suburbs, we'd also ask the mechanic straight out whether it suits the way the car's used, because RACQ suggests drivers who are mostly in slow city traffic think about whether a DPF vehicle suits them at all.