Engine stalling when DPF regenerating

[alexaescht]

Hi, for a while now our polo has had this extremely annoying/dangerous thing where every time just before the DPF light comes on (about a day before) it will start to run rough and will quite often stall when you depress the clutch coming up to a set of lights, or a roundabout. The car went into VW for half a week a while ago to replace an EGR valve and replace some vacuum hoses that were chewed by rodents and at the same time we told VW about the issue, they said that after these two things were replaced that it would not happen again. Well, yesterday the car started to show its telltale signs of beginning to regenerate the DPF (idling high, idle fuel consumption down, exhaust running really hot, engine becoming louder etc.) and what do you know, going downhill at about 60 km/h in 4th towards a red light and then depressing the clutch, the rev gauge goes from ~2,500 rpm to normal idle (800 rpm) then below that to about 600 rpm, then up to 1,400 rpm, then to 0 rpm.
We do generally short trips, so I can understand why the DPF is regenerating so often, but surely it shouldn't make the engine stall.
A big problem though is that VW said they can't fix it unless they can actually be there when it happens, which is difficult because most of the time it does it on the way to work in the morning which is in completely the opposite direction.
So does anyone know if this is a known fault and has anyone experienced it? If it happens again ill try to capture it on video to prove it happens.

[gavs]

Capture it on video, take it to the dealership and show them the exact issue. I haven't heard of this issue from anyone else around the world....

[alexaescht]

Ok, sounds like a good idea. I think that there is a thread in the Golf MK VI forum with a similar issue. Ill try to find it...

Here, a similar issue but not exactly the same: DPF blues

[Transporter]

The video is good idea. But, maybe more checking is needed to make sure that the rats didn't chew more than just the vacuum hoses, the rats also like the wiring and the air filters.

I also use diesel additive that helps with the regeneration, since my wife has only 16km to work and then back and except that she drives 3km and 8km trips to shops. The Tiguan spent doing these short trips for past 12,000km (total 20,000km) and so far no DPF issues.

[alexaescht]

Thanks. I suppose another option would be to take it to a different dealer (Burwin probably) and see what they can do.

[anglo_dude]

There is this report from the UK:

22-6-2012: VW is now admitting that 1.2TDI is not suitable for repeated short runs from cold. "15 months ago we bought a new VW Polo 1.2 TDI. We told the dealer our driving habits were mostly short journeys with several long journeys a year, 12-15000 miles/yr. After 9,500 miles the EGR system blocked and we were told this was due to too many short journeys. Soon after that, at the first service, the dealer handed us a VW Group notice about the DPF, dated march 2010, which contained specific warnings about unsuitability for short journeys. The last paragraph said "make sure you are aware of and understand the above guidelines before ordering a vehicle fitted with DPF." We had not been given this notice prior to purchase."

This is taken from Honestjohns website, which is a really good consumer website for cars in the UK:
Volkswagen Polo V 2009 - Car Review | Honest John

[alexaescht]

Hmmm, interesting. We had the front disc failure on ours at about the same mileage, and the DPF problems.
When we were looking for the Polo VW simply asked 'How many kilometres do you drive in a year?' (We do about 35,000 km a year) instead of asking 'how long are your average trips?'

More from that website:
"24-2-2012: Now three separate reports of premature failure of front brake discs at 15 - 18 months old and around 15k miles.

1-3-2012: Yet more problems reported with the DPF of Polos fitted with 1.6TDI engine that are not regularly driven far enough."

[alexaescht]

Oh, and as I said in my original post, we had to get the EGR replaced as well because it was malfunctioning and causing the car to enter limp mode.

[nomadx38]

Hey alexaescht,

First off I don't own a diesel car, I love my pet-trol-lol! But thinking about your problem I would say it could have somthing to do with a pressure sensor in the DPF. Just doing some brief research on the DPF apparently it burns off the soot by either injecting fuel directly into the DPF or by increasing exhaust temperature by means of late ignition or controled misfiring. The reason I say it could be a sensor is because the sensors monitor the back pressure on the exhaust and DPF to prevent damage to the DPF, engine and exhaust from the hot explosive pressure. Also the pressure can prevent combustion exahust from exiting the cilinder which can result in poor fuel economy, staling and lack of throttle response.

Why didn't the sensor throw up a check if its damaged? I would assume its the same problem I have with my DSG (cultch solienoid sensor doent work accurately so it drops the clutch every gear). The problem is that the electronic part hasn't failed compleatly so is still making a circuit and thus not throwing up an error. This is what I have and diagnostics show nothing wrong with the garbox. I went with the vw tech for a drive and within 5mins he said that's not right and I am now due in for a mechatronics unit and new clutches because of the damage that could have been caused to them as a result.

What would I suggest? Well before my test drive I went around the area a few times and noted when it would play up at certain speeds, braking, stop start on hills etc, and during the test told him to do it that way and that's how I showed him. You may have to do a similar thing if diagnostics show nothing wrong.

Also could try going through the mountains with high revs (you know a real spirited drive) to manually clear out the DPF and see how it goes.

[kaanage]

There is this report from the UK:

22-6-2012: VW is now admitting that 1.2TDI is not suitable for repeated short runs from cold.

Yes, this is why I hesitate to recommend the 6R TDi to anyone who expects it to be a city car