DPF regeneration & power loss

[cbr600ski]

Hi all

I am hoping one of you fine people might read this and think - yes, I know the answer!

I have a 2017 Caravelle 150DSG with 20k on the clock. It did c2k a year for 5 years until June 2022 when a family bought it and did 9k miles in 1 year. I have now bought it and am perplexed by the way the car runs.

Mostly it bowls along well, if very slow through the gears from D1 to D3. Then every so often it goes into DPF regen mode (I'm assuming), and gulps diesel whilst at the same time running really badly. Power loss accompanied by rough running, as well as a slight whiff of diesel smoke in the cabin. This can happen on a long journey for about 30-60 miles' duration - It knocks you from about 75mph to about 60mph - then suddenly it's happy again and bowls along as normal. I have been doing mainly long runs in it, and 1,000 miles since purchase, it's done this about 6 times. One of those, to be fair, was when it didn't get to finish its regen before I stopped so it had to do it again. It's not going into full-on limp mode, nor is it showing any engine lights.

The garage have run a full diagnostic on everything around the DPF/EGR/etc etc and there's nothing showing there either. No soot at the tail pipe and ash reading very low. No obvious splits in pipes or at junction points. I've changed to premium fuel on the advice of some threads on the forum but I don't think it's made a huge difference yet. I also know from one of the posts on here that some biturbos do the regen every 150 miles. I used to run a 164k mile T5, and whilst I love the Caravelle, and bought the 150 DSG to avoid the noise around the biturbo, the prospect of having this up and down power issue so frequently is perturbing me. It really affects your pleasure of driving on long distances.

Does anyone out there also have a car that goes into reduced power/rough running mode (but not limp mode) on dpf regens in the middle of a motorway or dual carriageway? And is this REALLY how T6s feel - regen every 150 miles?

Finally, assuming the garage has looked at everything (two of them now, actually) and drawn a blank, would anyone recommend a subscription to Carista to see whether I could get a more systematic dialogue with the car as to what it's doing?

Many thanks! Alex
Thanks for reading and any help.

 

[jimc91]

Can’t really help with this but if you do get a Carista it’s worth getting the DPF monitoring app to use with it as it gives much better data for you to monitor how often regens happen and you might identify a pattern. There’s a thread on here regarding the app

 

[mmi]

Any service history? By any chance cambelt/timing belt have been replaced recently?

Does anyone out there also have a car that goes into reduced power/rough running mode (but not limp mode) on dpf regens in the middle of a motorway or dual carriageway?

On the move there is no way to know it's doing DPF regen - definitely no change in power or rough running.

It knocks you from about 75mph to about 60mph

You mean it won't go any faster than 60 mph?


For proper diagnosis would need to take probably similar steps as below

204 DSG intermittent momentary power loss

Hi all, Desperately looking for some assistance! I have a 2018 204 DSG high line. Had it from 8k miles, now has 82k on the clock. I’ve done all of the servicing and maintenance on it as I’m very mechanically minded and my business is automotive electrical design. However, I have a fault that I...

www.t6forum.com

 

[cbr600ski]

Thanks for the thoughts guys!
Jimc1 - Thanks for the tip on the Carista.
MMi - I don't think cambelt/timing belt have ever been changed (only 20k miles on the clock).
I do know when it's regenning on the move (or perhaps it's doing something else and I'm just assuming it's regenning?), because you smell diesel smoke in the cabin and it does this run-rough nonsense. Then it clears and goes nicely, no smoke ingress once it's had its paddy fit. I have had the whole system checked and they tell me there's no diagnostic showing up, nor any cracks/dodgy pipe connections etc.
In answer to your question - no it's not like a power limiter at 60mph, but you need to put the right foot to the floor to get to the 75mph and it really doesn't want to go, whereas previously you were bowling along with about half-pedal, or even less, at the 75mph. And all on a largely flat road.
Thanks for link to the other thread.
Cheers all

 

[cbr600ski]

Any service history? By any chance cambelt/timing belt have been replaced recently?


On the move there is no way to know it's doing DPF regen - definitely no change in power or rough running.


You mean it won't go any faster than 60 mph?


For proper diagnosis would need to take probably similar steps as below

204 DSG intermittent momentary power loss

Hi all, Desperately looking for some assistance! I have a 2018 204 DSG high line. Had it from 8k miles, now has 82k on the clock. I’ve done all of the servicing and maintenance on it as I’m very mechanically minded and my business is automotive electrical design. However, I have a fault that I...

www.t6forum.com

Oh my goodness I have just read that thread you shared. Incredible. Not sure I understood it all, but the implication is that my obsession with the diesel smoke indicating DPF regen could be completely down the wrong track. The question is what / how on earth I get to the bottom of it, as I don't have your skills on that VCDS system analysis.

 

[mmi]

Quite a few confusing things going on - the 1st - diesel smoke without any cracks - you do have cabin heater blower running, no recirculation?

The question is what / how on earth I get to the bottom of it, as I don't have your skills on that VCDS system analysis.

Well, I´m more than happy to help/share the analysis part - just need to get VCDS data recordings Of course will help with setting up the VCDS if decide to take that route...

Ross-Tech: Distributor List

Ross-Tech VCDS HEX-V2 USB package for VW, Audi, Seat, Skoda cars (1996 on, 3 VIN limit)

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VCDS HEX-V2 Enthusiast 3VIN

Product:VCDS HEX-V2 3VIN, Manufacturer:Ross-Tech, Price:£225.00

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VCDS®HEX-V2 USB (3 VIN) Ross-Tech VCDS® HEX-V2 USB - Marshalls Industrial

Home User Kit, For use with a maximum 3 VINs Kit Includes: VCDS® V2 Dongle, USB Cable, USB stick (Software and Manual), Tough Plastic Carry Case.

www.mi-uk.com

VCDS® HEX-V2® Enthusiast – USB Interface(3 Different Cars) - Vcdsdiagnostics

Three(3) different cars(VIN numbers)

vcdsdiagnostics.co.uk

 

[TC7890]

Hey @cbr600ski - did you ever get to the bottom of this issue? I'm experiencing really similar symptoms and it's suuuper annoying!

I have a 2016 T6 T30 Highline 2.0 6-speed with 60K on the clock, which 90% of the time runs absolutely fine, no issues, pulls through all the gears. Then as soon as the regen cycle kicks on it's like it loses all low down power, and between 1,000 - 1,200-ish revs the power delivery is really lumpy and fluctuates a lot, although the idle seems to be consistent.

Here are a couple of videos showing the symptoms:

1st video stationary, with constant pressure applied to the throttle pedal:

2nd video under load pulling away from stationary:

It is also constantly telling me to shift down in the MFD, even at speeds I know are easily comfortable for the gear I'm in, and when decelerating in gear it can sometimes become lurchy.

I can't say it's noticeable particularly at higher speeds as your issue was, but it makes driving really difficult as soon as you leave the motorway and need to pull away from a set of lights!

@mmi - you asked whether the timing belt had been changed recently on cbr600ski's van, it has been done recently on mine, could this be involved? The van doesn't seem to have any issues when not running under regen.

Any help or input greatly appreciated!

Cheers

 

[cbr600ski]

Hi there
No, I am pulling my hair out with the problem. It seems to be getting worse too.
So, I have now been to three VW garages all of which have done the computer diagnostics and come back flawless and with no stored error codes. One did an extended road trip and also drew a blank. None of the technicians have ever heard of this before...

However, I have done 2 x trips to the Alps and so plenty of time to assess the specific symptoms:
- Randomly, sometimes every 150 miles, sometimes non stop for 100 miles, the engine suddenly gets rough and there's no "oomph".
- It consumes massive amounts of fuel during this period. E.g. running along perfectly happily on a French autoroute at 80mph and suddenly silly mode kicks in, the engine feels like it's come off boost, somehow, and wants to drop to 65mph. If you let it drop to 65mph you can maintain the MPG. If you throttle up to keep it at 80mph, the constant MPG on the trip computer will fall from c35mpg to c25mpg.
- At this speed, the DSG is in D7 so I don't notice the gear problems.
- I sometimes notice the heat system in the car goes a bit haywire, it suddenly gets hot in the cabin - so I wonder if it's DPF'g whilst it's doing this.
- And then, with no obvious reason, it goes back to being normal again.

At slow speeds, it's harder to spot, but I've now done enough miles to be able to confirm that:
- The same thing happens, i.e. rough running at all speeds, useless acceleration (but not limp mode) and MPG falls.
- And in addition, the gearbox doesn't know what to do. So instead of the DSG behaving properly, it's all over the place, changing up really late and "dragging" itself. This really spoils the way the car drives.
- And I sometimes get diesel fumes/smoke in the cabin. Not awful, but there.
- When it's like this for days on end, it's SO ANNOYING.....

Allegedly my car is "normal" on its DPF cycle (i.e. low ash deposits etc) and I trust MMI on this forum who says slow running shouldn't be linked with DPF regens. I've tried using fancy fuel (in fact I don't use any other), and I've tried running a turbo cleaner through the system in case it was just something stopping the turbo working.

I am wondering now whether it's something to do with a dodgy fuel pressure regulator or fuel sensor - because it's clearly trying to push gallons of fuel through the system when it's doing whatever it's doing. But the fact that it's started involving the DSG box worries me. Again, I've talked this last week to my garage and they are clueless as to what it could be.

So anyone who knows anything, please help! There's two of us now with similar problems.

 

[cbr600ski]

PS. I forgot to say, I've been trying to take up MMI's recommendation to get running data. I spoke to Carista and they couldn't help because it's static readings I think. And I spoke to the Ross Tech people but I need someone to help me set it up and all of my local garages here have said they don't do this. Sigh.

 

[mmi]

@mmi - you asked whether the timing belt had been changed recently on cbr600ski's van, it has been done recently on mine, could this be involved?

Shouldn't be - just tried to exclude things because if the belt was a tooth off it possibly could have an influence because during DPF regeneration engine runs in a different "mode". Anyways, not likely cause when engine at least sometime runs fine.

PS. I forgot to say, I've been trying to take up MMI's recommendation to get running data. I spoke to Carista and they couldn't help because it's static readings I think. And I spoke to the Ross Tech people but I need someone to help me set it up and all of my local garages here have said they don't do this. Sigh.

Indeed, a VCDS proper data log would be more than helpful - at least to exclude things which are easy to monitor through OBD diagnostic port - e.g. crankshaft and/or speed sensors, air mass sensor, fuel pressure, etc. instead of just replacing parts.

Note: for a proper (fast enough ) recording either VCDS HEX-V2 or HEX-NET interface is needed. The older ones are simply too slow to catch possible glitches.

 

[pmblue57]

Hi Guys, just to let you know it’s not the fuel temp sensor.
I’ve got the same problem on my 2019 T32 highline with manual gearbox. When it happens on mine I drop it down to 3rd gear and thrash it at 4,000 RPM. Seems to clear after 10 minutes.
Makes me think this is a DPF blockage and thinking about removing it altogether.

 

[FerrisBFW]

If you are south try Tom at Retro Resus, this place really know their transporters/caravelles

 

[dane]

We had a similar thing happen yesterday and it turned out to be the fuel temp sensor.
The cable of the sensor is run over a rubber pipe, and over time, with the vibrations of the engine, the cables insulation had rubbed/deteriorated exposing the conductor (even braking some of the strands). Got a silver van out and he sorted in an hour. The chap said he’d seen it a few time before to as its how the cables installed at the factory.

Thankfully we took out the all in plan in January so with other items going tits up (head unit, possible steering rack/pump) it looks like its already paid for itself.

 

[DXX]

Hi Guys, just to let you know it’s not the fuel temp sensor.
I’ve got the same problem on my 2019 T32 highline with manual gearbox. When it happens on mine I drop it down to 3rd gear and thrash it at 4,000 RPM. Seems to clear after 10 minutes.
Makes me think this is a DPF blockage and thinking about removing it altogether.

If you suspect the DPF is blocked I would advise not to keep driving it and to get it diagnosed and repaired.
There seems to be a trend of failing DPFs destroying turbochargers and taking the engine with them.
Removing the DPF isn’t really a good option, the chances of it being detected at an MOT are high and the Gov’ has just published a paper indicating that MOT emissions testing will be tightened.

 

[FerrisBFW]

If you suspect the DPF is blocked I would advise not to keep driving it and to get it diagnosed and repaired.
There seems to be a trend of failing DPFs destroying turbochargers and taking the engine with them.
Removing the DPF isn’t really a good option, the chances of it being detected at an MOT are high and the Gov’ has just published a paper indicating that MOT emissions testing will be tightened.

can you share the paper?

 

[DXX]

can you share the paper?

Government committed to MOT modernisation as consultation concludes

First MOT test to remain at 3 years from registration and annually thereafter while government works to establish a programme of longer-term reform for MOTs.

www.gov.uk

https://assets.publishing.service.gov.uk/media/65e731863f6945a00603606d/date-of-the-first-mot-test-consultation-response.pdf

 

[pmblue57]

We had a similar thing happen yesterday and it turned out to be the fuel temp sensor.
The cable of the sensor is run over a rubber pipe, and over time, with the vibrations of the engine, the cables insulation had rubbed/deteriorated exposing the conductor (even braking some of the strands). Got a silver van out and he sorted in an hour. The chap said he’d seen it a few time before to as its how the cables installed at the factory.

Thankfully we took out the all in plan in January so with other items going tits up (head unit, possible steering rack/pump) it looks like its already paid for itself.

I tried that last week but it didn’t make a difference. As it was only £10 I thought I’d try another one.
So far, fingers crossed it’s not played up at all.
Thanks, if it wasn’t for your comment I wouldn’t have tried again!

 

[dane]

I tried that last week but it didn’t make a difference. As it was only £10 I thought I’d try another one.
So far, fingers crossed it’s not played up at all.
Thanks, if it wasn’t for your comment I wouldn’t have tried again!

Ahh great news.