Cleaning a blocked DPF

[patrickhorton]

I have recently cleaned a blocked Diesel Particle Filter DPF on an A4 TDI 170. I hope the following experience is useful to someone.

I removed the filter and used an electric hot air blower to burn out some of the carbon deposits. This took the filter back to a state where the car could regenerate the filter itself.

This is quite a long story so will only be of interest to someone with the same problem.

When I bought the car a month ago the DPF warning symbol was lit on the dash and glowpug and emissions lights were on too. After a 60 mile drive in limp home mode from the auction, the dpf light was still on and no regeneration had taken place. I presume the threshold at which the filter is too blocked to do an auto regen had been exceeded. VAGCOM showed fault code 008194 and measurement block MVB 075.3: Particle Filter Load was at 174%.

Research on the web showed that a dealer was likely to recommend replacing the DPF at over £1000. Emergency regeneration procedure is described in the Ross-tech website but this looked risky as it gives the following warning "If the Particle Filter Load is above Specification the Particle Filter needs to be replaced since the car may burn down when regenerating". The only safe option seemed to be to take the filter off and confirm a real blockage and try to clean it off the car.

With the filter on the bench I could see it looked surprisingly clean inside but simply trying to blow through it was quite hard. How the engine runs with this back-pressure, I don't know. I did a test with a powerful blower and a simple flag to give a benchmark flow measurement for before and after cleaning tests.

I can give more details if anyone is interested but the basic method is this. I used an electric hot air gun (bit like a paint stripper) which is designed for lighting fires. This tool was arranged to push a very small flow of air through the filter at about 600degC. I ran this setup for about 2 hours and rechecked the flow. There was a noticeable improvement. I gave it another 4hours and decided it was worth putting the filter back on the car.

With the filter replaced I took the car out with VAGCOM connected. The MVB 075.3: Particle Filter Load immediately started to fall from 174% at 1% every few seconds. As the car warmed up the exhaust temperatures were in the range 200 to 400C depending on engine load. This remained well after normal coolant temperature was reached. The filter load contiued to fall at the same rate. (my interpretation of this is that the pressure measurements around the filter are used to create the loading value with a very long time constant to avoid eratic readings - I suspect the loading was already very low and it was taking a long time for the calculation to catch up)

Then at somewhere around 80% something amazing happened. The exhaust temp shot up to 800C and hovered around there for the next few miles. The threshold for preventing auto regen must have been crossed. The load value contiued to fall to about 12% and then the exhaust temp dropped back to the usual 200 to 400 range and .... wait for it... the DPF warning light went off. If I remember correctly the glow plug light went off sometime before.

This is pretty much the full process though in my case there was an underlying fault at the root of the problems. A punctured vacuum line had put the car in limp home mode (emissions symbol on dash) which presumably led to eventual sooting of the filter coupled to repeated cold starts at the car auction. It is usful to note that this fault did not prevent an auto regen of the filter once it had been cleaned on the bench.


Finally a big thank you to all people who submit to forums. Without these resources on the web, I would not have had enough background info to attempt this idea.

[Alan02]

Luckily i dont have a DPF on my model,but pleased to hear yours is now sorted.And a good write-up for those who do have problems with the DPF !

[a8 tech]

If you follow the correct process and all the associated sensors are correct then emergency regen is required only if you have failed to carry out the correct driving profile when prompted by the regen light displayed on the dash.In your case the emergency regen would simply have done this for you but only via vcds or vas pc.At this time of year we find the tubing pipes freeze causing incorrect pressure readings but most common cause I have found is the g450 sensor.
The emergency regen is pretty successful but you need a good 20 mile stretch of motorway and a second person observing the vcds readings.
You have gone to alot of effort so I commend you but there was no need.
If in doubt next time check the exhaust sensors read correct and g450 pressure is within spec followed by removing the g450 pipes and cleaning them.



NEVER IGNORE THE PRE REGEN WARNINGS AND DONT REMAP OR ADD CHIP BOXES TO PD DPF ENGINES
Attachment 7645


If you see either fault code

08194 P2002 particle filter bank 1 - malfunction

this is your fault code and you require the ecu flash updating and this in turn with the emergency regen would resolve your issue (The dealer would not have suggested a new dpf unless this failed !!!!!).The update heats the dpf quicker amongst other mods associated with dpf monitoring and ash content

09263 P242F particulate filter maximum loading exceeded


Check with your dealer for the relevant ecu update or post your engine code and also a current vcds log with address 01 full data so I can see your sw version

[patrickhorton]

If you follow the correct process and all the associated sensors are correct then emergency regen is required only if you have failed to carry out the correct driving profile when prompted by the regen light displayed on the dash.In your case the emergency regen would simply have done this for you .....
You have gone to alot of effort so I commend you but there was no need.


If you see either fault code

08194 P2002 particle filter bank 1 - malfunction

09263 P242F particulate filter maximum loading exceeded


Check with your dealer for the relevant ecu update

Thanks for the comments especially the attached file. Wish I had asked you before...
I'm a bit puzzled though about the DPF loading percentage. Mine was 174% according to VCDS and your attached file says >90% cannot be emergency regen'd. But since I didn't get fault code 09263, perhaps that tells me it would have been possible.
As for doing a regen earlier, the car was bought clogged up.
An ECU update for DPF is shown in the service history at 80k. Car now has 143k (on a 56 plate!)

Cheers
Patrick

[a8 tech]

What soot content do you know see?
To confirm post your mvb from 68 to 75 and your current ecu part number with the sw version

[patrickhorton]

My VCDS is not available at the mo. Will report MVBs etc. when I can.
The service invoice from Audi for August 08 says "Carried out Worshop Action 23B9" and "Carried out software upgrade for DPF as required".
Cheers
Patrick

[randall977]

Is there any rule to which cars Audi put the DPF on? Mine is a November 2006 TDI 170...I've just ordered a Diesel box btw...

[patrickhorton]

What soot content do you know see?
To confirm post your mvb from 68 to 75 and your current ecu part number with the sw version

Got VCDS back now. (because of new disaster)
MVBs you asked about are [with engine not running] :
68 - 13.5%, 85.16, -20.1%
69 - 00000000, - , - , 00000000
70 - 00000000, 0.0s , 0.0, 0.0
71 - 0/min, 0.0mg, 120BTDC, 0.0KW
72 -
73 - 0.8l, 12km, 0h
74 - 0/min, 8.9C, 1.000, 0.00mg
75 - 8.9C, 5.3C, 13.5%, 3.5C

ECU Part No [is this h/w no? which is -] VAG 03G 906 018 AQ
SW version [is this soft coding which is -] 0000072

Not sure if any of above is much use with engine not running.

And that is the new problem... engine cut out today and won't run. something to do with injector electrics?
Got fault codes:

004160 - supply voltage A for injectors circuit malfunction P1040 - 006 short to plus intermittent, freq 2, 1856rpm

and

008518 - supply voltage for fuel injector grp A : Open circuit P2146 - 009 - open or short to ground intermittent, freq 9

I plan to somehow check injector wiring loom. Reckon its worth changing regardless. Worried dealers will sell me injectors which may not be required (at £500 a pop so I hear).

Did about 500miles since DPF fixed. Everything seemed to be fine till today.

Any feedback very welcome.

Cheers
Patrick

[Adman]

Hi,

I had the same happen on my 170. The engine cut out and would not start. When they got into the garage, it posted two fault codes can't remember what they were but it needed a new injector. They did change the injector wiring loom aswell as plastic bits were broken off.

I hope for you it isn't the injector as it was about £500 for the part.

Cheers

Ad

[a8 tech]

Got VCDS back now. (because of new disaster)
MVBs you asked about are [with engine not running] :
68 - 13.5%, 85.16, -20.1%
69 - 00000000, - , - , 00000000
70 - 00000000, 0.0s , 0.0, 0.0
71 - 0/min, 0.0mg, 120BTDC, 0.0KW
72 -
73 - 0.8l, 12km, 0h
74 - 0/min, 8.9C, 1.000, 0.00mg
75 - 8.9C, 5.3C, 13.5%, 3.5C

ECU Part No [is this h/w no? which is -] VAG 03G 906 018 AQ
SW version [is this soft coding which is -] 0000072

Not sure if any of above is much use with engine not running.

And that is the new problem... engine cut out today and won't run. something to do with injector electrics?
Got fault codes:

004160 - supply voltage A for injectors circuit malfunction P1040 - 006 short to plus intermittent, freq 2, 1856rpm

and

008518 - supply voltage for fuel injector grp A : Open circuit P2146 - 009 - open or short to ground intermittent, freq 9

I plan to somehow check injector wiring loom. Reckon its worth changing regardless. Worried dealers will sell me injectors which may not be required (at £500 a pop so I hear).

Did about 500miles since DPF fixed. Everything seemed to be fine till today.

Any feedback very welcome.

Cheers
Patrick

Remove the rocker cover and disconnect the injectors one by one until the engine starts and then replace the defective injector or injectors.