Particulate filter problems after emissions recall

[voxmagna]

I thought the reason behind the fix was to make the emission parts work when they were not working before?

If you think you are not getting regens (bet you are?) check the dpf ash and soot levels, 'cos I think that mileage without regens would have soon clogged it up.

[Urrell]

There is an active DPF regen done about every thousand miles irrespective of it's soot loading.

[Ryeman]

Don’t confuse particulate emissions  - DPF

with

NOx emissions  - combustion temperature control via the EGR cooler valve unit.

However

If the old cheating system was running higher combustion chamber temperatures, it was probably producing LESS particulate matter ....but MORE NOx gas.

In that case, the fix by lowering combustion temperature, is resulting in a less efficient burn resulting in more particulate content making more DPF regen necessary .....and also showing up as lower fuel economy......it’s the dichotomy that has no solution it seems.

 

(In time, I imagine a DPF replacement/service regime run efficiently and relatively affordably  by the non dealership sector..........the EGR cooler and inlet manifold fouling however, from reports, seems to be a significantly more complex, labour intensive issue.....and not just VAG vehicles)

Edited 21 December, 2017 by Ryeman

[Ryeman]

Of course the latest diesels with AdBlue get around it by allowing higher burn temperatures and then dealing with the consequent NOx by injection of  the DEF  - urea based, into the catalyst .

NOT doing it that way was what led to the cheat being developed and implemented.

[silver1011]

It is well documented now that the emissions fix puts additional loads on both the DPF and EGR i.e. they work harder now than they did before the fix.

 

If you are experiencing issues with either the DPF or EGR after the fix then it is highly likely that it is directly related to the fix.

 

So prevalent are the issues and customer complaints that Skoda UK have initiated a thinly veiled warranty called a 'trust building measure'...

 

http://www.skoda.co.uk/owners/dieselinfo/trust-building-measure/

[Ryeman]

^^^^^^^ but do you have to tick the ‘trust’ options box first?.

[voxmagna]

That's what I had, but you have to have the car regularly serviced by a Skoda dealer and there's a let out for wear and tear. That's why I concluded in my case that a badly gunged up throttle valve, manifold and whatever else would allow them to deny the claim in full, or at the very least leave me with an expensive labor bill. If your car was low mileage and less than 3 years old I think you might be o.k. I think you still need to be sure that all your emissions components are clean and it will it be hard to argue the fix caused faults, when the EGR system wasn't working properly before - although that's how you bought the car.

 

The reported replacement of temperature sensors is rather worrying if they are failing? Temperature sensors capable of working at high temperatures would normally be disimilar metal K-types which usually have a maximum temperature of around 1100 degrees C. although more common types are up to around 800 deg. C.  A sensor like this that has been in service at lower temperatures for a long time might not cope with a sudden change to what was its normal working temperature.

 

We need to hear more from members who have successfully claimed under this 'trust building measure' ? I hope the requirement for regular service isn't a let out for Skoda to modify their fix as complaints roll in? VCDS tell me my ECU has been programmed twice, but I'll rescan it to let others know the reference code for the second reflash.

[corn1]

Hello I have problems with my yeti after recall. Been reading messages and would like to know what is a regen and how does it work. new here

cornell

[voxmagna]

Hi, you don't say what problem you have? If you have had the recall done I suggest you take it back to the Skoda dealership. There are some weasel words about them supporting problems after the EA189 fix was done. My thoughts are it can go 3 ways:

 

1. They say your problems are caused by mileage and worsening engine condition before you had the fix done and they will not cover you on parts and labor for repairs. They could argue their fix works on good clean engines, but can produce premature faults when applied to engines with mileage and used for short journey local driving.

2. They offer you a sweetener and say they don't think their fix is responsible on its own and they will cover only part of the cost as goodwill, but you will still pay a lot.

3. They put their hands up and say they will cover all the work and parts cost for any part of your emission system that has now failed and produced a fault, irrespective of the condition of your engine emission parts at the time.

 

You have an older Yeti with some miles on it? IMHO you were probably heading for work to be done de-clogging or replacing emission control parts anyway and the EA 189 fix has stretched those parts to throw up warnings now. How much longer could you have gone without the fix? Read up on diesel EGR valve, throttle valve, and dpf. They are a common problem on modern diesels, even without the fix.

 

I'm not guessing which option they will take, but many on this Forum will want to know how Skoda U.K are responding to problems like yours (and theirs!).

Good luck.

.

 

[Sad555]

 

I thought any exhaust system failures were covered for 2 years AFTER the fix/fail in Europe and 10 years in the U S A,so called (good will) without admitting any liability.

 

 

[Jonathon1]

In my case, the handbook says in order to clear the yellow Dpf warning light, you have to drive at 40 mph per in 4th gear for at least 15 minutes continuous. . Then it’s suppose to clear it, but it doesn’t. I have now found out on the last two occasions that it has to be driven down a motorway at max speed for at least 30 minutes where  the oil temperature reches   95º

this is happening every 3 weeks on an average monthly mileage of 800  in a mix of country lanes and B roads with no congestion.

 

[Frenchtone]

On my Mk 1 140 the normal running oil temp here in West Finistere is around 95-97, but I forced a regen Saturday whilst auto routing, the temp reached 103/105 running at approx. 2500 - 2700 rpm in the relevant gear at an indicated 119kph (real world 110kph)!

[voxmagna]

3 hours ago, Jonathon1 said:

In my case, the handbook says in order to clear the yellow Dpf warning light, you have to drive at 40 mph per in 4th gear for at least 15 minutes continuous. . Then it’s suppose to clear it, but it doesn’t. I have now found out on the last two occasions that it has to be driven down a motorway at max speed for at least 30 minutes where  the oil temperature reches   95º

this is happening every 3 weeks on an average monthly mileage of 800  in a mix of country lanes and B roads with no congestion.

 

 

That info is about right except the engine coolant should also be above about 60 deg C. If you start the run with a really cold engine, the regeneration cycle only starts when that temperature is reached. 4th gear is to ensure the engine rpm is above 2k rpm. We find on motorways 60mph at just over 2K rpm is safer, but allow 25 minutes. If you start a manual regen. the dpf light will go out when it's finished. The dpf light should only come on when you trigger a manual regen. with diagnostics.  In automatic engine managed mode, it should only come on to warn you that your dpf is heading towards too high soot load - we have never had this. It shouldn't do this if one regen. is incomplete because it appears to keep trying, but all the time a regen. tries and fails, the soot load is increasing to the lower threshold, which I think is why you keep getting the warning?  If your soot and ash loads are already near the threshold, you won't have so much headroom for failed regens and the warning will come on sooner and more often.

 

Why did they keep all this secret and not have a dpf dash warning come on and go out with normal driving?

 

The handbook should also say that if the dpf light doesn't go out, the calculated soot or ash levels may be above their safe threshold for a regen. and it won't start. It's the dreaded 'Take to garage' scenario' for further investigation and possible a new dpf. In your case, get the stored dpf soot and ash levels checked. If they are o.k with plenty of margin left, then your driving routes, speeds, rpm and time on them is insufficient. For the last few years we have always tried to keep our tachos at 2K or just over. Around town that means 3rd & 4th gear most of the time.

.

Edited 30 January, 2018 by voxmagna

[Jonathon1]

I have just driven 300 km  to Bordeaux & back on the autoroute with first of all the dpf warning light on then all three and limp mode. So it can’t be short journeys. The comment about the EGR cooler valve iis interesting.

Skoda Perigeuex have at last (after 15 months with numerous regenerations, 2 temperature contrôle sensors  and telling me I was doing too many short journeys) agreed to have the car in for 3 days to do some extensive tests as they have finally admitted that there may be a post fix issue.   So here’s hoping!

[Ryeman]

27 minutes ago, Jonathon1 said:

I have just driven 300 km  to Bordeaux & back on the autoroute with first of all the dpf warning light on then all three and limp mode. So it can’t be short journeys. The comment about the EGR cooler valve iis interesting.

Skoda Perigeuex have at last (after 15 months with numerous regenerations, 2 temperature contrôle sensors  and telling me I was doing too many short journeys) agreed to have the car in for 3 days to do some extensive tests as they have finally admitted that there may be a post fix issue.   So here’s hoping!

To me the EGR cooler valve unit is going to have to work harder (to reduce combustion temperatures) at the higher speeds and loads.  That carbon fouls the cooler and induction tract.  SCR (adblue) reduces, but doesn’t eliminate,  the rate of fouling.

I would expect sustained higher speeds are relatively beneficial for the DPF however.   You can’t win it seems.

[Yety]

Re the posts above: a very good selection of what the general consensus seems to be. I have contact with JLR development guys on a regular basis and this is the scenario they knew about when the scandal broke in 2015? All the manufacturers know what's going on, they "helped" the EU draw up the emission testing regimes in the first place - they mostly all have their skeletons in cupboards which they are "dealing with".

I guess VAG were naughty when they realised they couldn't get there way back, and a testing dodge/fudge forced them to try and go to push as far as they go could go to comply.

The other thing not helping, is that modern diesels are not the old slow revving load luggers of the past, and need to run within a fairly narrow window - and oldies like me need to change driving styles, not easy.

 

I've not had the "Fix" done, and my ash level is 0.07 of whatever on VAG DPF at 84K. 

[voxmagna]

I can only report back so far on results of monitoring exhaust gas (EG) temperatures on an older 2007 pre-common rail diesel: 

 

My in-car exhaust gas monitor circuit schematic needs changing for the common rail engines because they cheaped out and used thermistors for the sensors. If you ever see reports of sensor failure I will bet  it will be S1 on engines after 2012? On the older Tdi I forced a driving regen with vcds (dpf light on) much the same as Jonathon1 had (unless he had other problems putting the light on?) My engine was warm and as soon as I set off the EG temperatures shot up, but only after reaching 35mph and around 2k rpm if I dropped the road speed to 33mph the EG temperatures dropped right down. Those speeds are lower than what I had read in the V.W SSPs. I could easily hold speed and rpm at those levels without a fast motorway drive. Then after about 15 minutes my DPF light went out and the EG temperature dropped like a stone. Those responses are what I would expect from a regenerating cycle. This 2007 BMM engine has had no work done on the EGR valve, DPF or throttle valve in 50k miles.  I know short stop driving isn't good for the dpf, but 35mph @2k on the older engine may explain why i've never had any issues or a dpf light come on.

 

When I've finished the new circuit schematic I'll let you know what I find on the 'fixed' CFHC engine which had the EGR cooler replaced before the fix and the throttle valve recently de-gummed. With its ECU fix it should do DPF regens like a new engine.  I would like to think DPF regens would behave the same as my older engine?

 

Commenting on jonathon1s problem: When the dpf light has come on it will not finish a regen cycle if the exhaust gas temperature in the DPF cannot be maintained at the required level for the time they set, which might explain why it now stays on for so long? As I said earlier, with an ECU fix or not, DPF warning lights shouldn't come on unless there's a fault or it's telling you your driving style isn't getting the engine hot enough. From what I've seen with my in-car tests, DPF regens should be occurring normally in the background and DPF light on is a wake up call. We talk about regeneration as if it's a single event, but I don't think it is. If you were driving at motorway speeds for hours when the DPF temperature is already elevated, I don't think you would see frequent 'forced' regeneration events? I think Jonothon1s problem started when the dpf couldn't reach the elevated temperatures during normal driving regenerations. Their regen. management system is probably stupid. It doesn't log the accumulated time the dpf temperatures have been maintained before being cut short. It says 'DPF regen 'incomplete - start again' and waste more fuel'. I think that's why we now read of engine bay fans running on after parking in cold weather. It's another wake up call for aborted DPF regen cycles.  You don't want your Skoda overheating and setting fire to loads of cars in a multi-storey car park. My advice to Jonothon1 before condemning the ECU fix is to put his car into regen. mode with the dpf light lit, monitor the DPF temperatures and go for a drive at least 15-20 minutes long (It doesn't have to be Bordeaux).

 

During that time the DPF temperature should hold steady at over 700 deg.C. I don't know yet what the minimum road speed would be for a CR engine, but a temperature readout will show that. If DPF temperatures are not reaching those temperatures then look at the throttle and EGR valves because they control the air supply to starve oxygen and raise the EG temperature. These are checked for abnormal faults at key on and during driving, but tend to be tests on end of range. If the valves are only partially opening or closing, a fault may not be given but there is insufficient control of the air supply to raise EG temperatures for the regen. to finish in the time they allow. I should add that if the dpf is now more clogged they will stop the high regeneration temperatures from being reached unless forced with diagnostics. If the DPF clog is too severe, the system won't let diagnostics force a regeneration for safety reasons. Driving long journeys with the DPF lamp lit risks permanent DPF clog and expensive replacement.

 

If you are lucky enough to own VCDS diagnostics and are a short journey driver, I think forcing a driving DPF regen. every so often is a good thing because it checks that once the light is on, it should go off after 15-20 minutes confirming the required high EG temperatures have been sustained and a regen.cycle finished o.k. If you look further at soot and ash levels these should be kept as low as possible, although ash values will always increase some. I'm disappointed that VAG switched from platinum EG sensors to cheaper thermistor type on the newer CR engines, so blame them not me if you force DPF regens more often and get faulty S1(?) EG sensors!

.

Edited 26 February, 2018 by voxmagna

[voxmagna]

I'm adding this point about CR engine sensors using the thermistor type. CR engine EG sensors can be two thermistor types - 'C' type for very high temperature with restricted range and 'E' type for a wider range at lower temperatures. The highest temperature S1 EG sensor pre-turbo in the exhaust manifold is different to S2(if fitted) S3 (dpf) and S4 post dpf.  S1 sensors measure about 6M ohm at 20 deg. C, whereas the S2,S3,S4 sensors measure about 25K ohm. Unlike the S2-S4 sensors, if you disconnect an S1 sensor you will NOT get a dash warning at key on because the ECU cannot tell the difference between a connected sensor and an open circuit! I suspect when driving, the S1 sensor is compared for expected voltage value with the other sensors when the engine is hot and only then will you get an S1 sensor fault?

 

Now I've shared the 20 deg. C resistor values you can do initial checks on a suspect thermistor with an ohmmeter - but don't get caught out by the high starting resistance of the S1 sensor, different to the others!   These thermistor sensors have a usable temperature range up to about 900 deg.C. That's not the same as 'expected life' which I doubt you will get from a sensor manufacturer. But if you have more frequent DPF regens with very high EG temperatures you can expect thermistor type sensors to have a shorter life. 900 deg.C seems to be the current technology limit for thermistor sensors and I've seen EG temperature going higher than this. Without doing a regen., EG temperatures at the manifold can exceed 900 deg.C on a re-mapped engine under very hard acceleration! Platinum resistance and 'K' type thermocouples can go to over 1200 deg. C.  Unfortunately, you cannot easily switch sensor types because thermistors are negative temperature co-efficient and very non linear. Well done V.W/ Skoda!

 

NEVER consider fitting a cheaper used sensor on a CR Tdi engine, especially after an ECU fix. I think EG sensor faults on CR engines after the ECU fix will will become more common. V.W/Skoda might argue out of a warranty repair for a very badly clogged emission part soon after the ECU fix, but I think anybody would have a good case for replacement EG sensors under their fix warranty, although don't expect them to last too long if they have increased the frequency of DPF regens.

.

Edited 26 February, 2018 by voxmagna

[weasley]

7 hours ago, Ryeman said:

To me the EGR cooler valve unit is going to have to work harder (to reduce combustion temperatures) at the higher speeds and loads.  That carbon fouls the cooler and induction tract.  SCR (adblue) reduces, but doesn’t eliminate,  the rate of fouling.

I would expect sustained higher speeds are relatively beneficial for the DPF however.   You can’t win it seems.

 

I'm not sure that's quite right.  The EGR valve will not have to work harder, per se, just at different opening angles for different amounts of time.  It's possible that the EGR valve is being asked to operate in a previously unused portion of its range which may already be fouled.

 

SCR happens fully in the exhaust, so shouldn't impinge on EGR operation at all.  What SCR does do is allow the engine to be operated at a hotter temperature, hence being more thermally efficient, reducing PM but generating more NOx which can be caught by the SCR in the exhaust.

[voxmagna]

I'd agree with that. IMHO what I'm suggesting is all the parts (including temperature sensors) may be 'working' of a fashion. Diagnostics tends to check extremes on motor controls to set a fault. If for any of the reasons I explained earlier, the EG DPF temperature cannot be achieved and sustained within their time window, at first nothing happens. Then It tries and tries again but never completes a regeneration. All this time the DPF soot and pressure levels are being monitored, regen. is tried again and again until at some point and unusually, the DPF fault light comes on because the fault has been there a while and you never knew.

 

As you say the valves work together to starve the engine of air and push up EG temperature in the dpf. I could think of several hypothetical fault scenarios but here's one: Lets say your thermistor sensors (S3?) are off their manufacturers curve due to ageing and repeated thermal stress? Regen. will be started when the ECU thinks it should be necessary. The ECU has to read the EG sensors and assume their curve characteristics have never changed, because the translation of non-linear voltage to temperature is done by fixed data tables in the ECU. At very high EG temperatures, thermistors will be at the top of their curves where most deviation from spec. and self heating is likely to occur.  But this is a critical area for temperature accuracy because EG temperature sensors control extra fueling and oxygen starvation during dpf regen. Your car thinks its DPF has been regenerating but the sensors were not telling truthful temperatures and soot was not converted. Eventually this inefficient background regen. increases soot load whose calculation algorithm doesn't use temperature and your DPF light comes on. That's why I suggest caution and relying on diagnostics to report high EG temperatures from these thermistor type sensors, because wrong voltage in will be wrong temperature out.

 

On my older non-common rail V.W I attached my EG temperature monitor design to the the S1 sensor by mistake.  But wow was that revealing! I wasn't looking at temperature values smoothed by the ECU but the real time fast EG temperature changes in the hottest place at the manifold, produced by a platinum resistance sensor. Real time EG temperatures can exceed 900 deg.C under hard acceleration! When I started a regen. cycle for a test drive I was amazed at how high temperatures were and how tight the EG temperature control was for speed and rpm changes, it just stays rock solid.  DPF regeneration carries real fire risks which I can now appreciate because 900 deg. C is about the temperature of red hot steel wire.

 

Most are completely blind to if and when a dpf regeneration occurs and whether it was successfully completed or not because there is no in-car indication.  I don't think garages have a cat in hell chance of working all this out If there's no fault code or randomly changing parts doesn't work for them. Unfortunately for us, checking the EGR assembly with eyes on the parts is a very expensive repair bill. The behavior of the exhaust gas temperature management is key to checking the system as long as you don't rely 100% on temperatures which diagnostics gives you.

[voxmagna]

If you want a solution for troublesome thermistor sensors in CR engines, there is nothing I've found from a rare (i.e small) number of manufacturers that exist with a virtual monopoly. The working temperature limit for thermistor based technology is about 900 deg.C but their stability is affected by cycles of extreme temperature. You will be frustrated searching for higher temperature alternatives, because their characteristics are a close secret held by the manufacturer. The best solution will come from Skoda, so complain like hell if you get EG sensor failures after their ECU fix. The EG sensors are a really important part of the CR engine design with virtually no work a rounds. If they replace an EG sensor, I doubt very much if it will be an improved higher temperature part, the technology at the moment can't do it, the ECU is already coded with the reference curve data or formula and the replacement will probably fail again.

 

I have a very radical idea how they could be replaced, but I'll wait and see if others can get there.

[Ryeman]

4 hours ago, weasley said:

 

I'm not sure that's quite right.  The EGR valve will not have to work harder, per se, just at different opening angles for different amounts of time.  It's possible that the EGR valve is being asked to operate in a previously unused portion of its range which may already be fouled.

 

SCR happens fully in the exhaust, so shouldn't impinge on EGR operation at all.  What SCR does do is allow the engine to be operated at a hotter temperature, hence being more thermally efficient, reducing PM but generating more NOx which can be caught by the SCR in the exhaust.

I was meaning that SCR limits EGR intervention by post combustion DEF injection immediately prior to the catalyst, thus allowing more efficient higher temperatures with the added benefit of reducing particulates also.

I would expect the lifespan of both to be extended, but also adding even more complexity.

[Ryeman]

Either way I can see why diesels in light vehicles are being dropped from the production line, ie  - the figures no longer add up.

We now have 2 clean diesel like small capacity petrol powered cars which are quieter, more powerful, similarly low rev torquey and not much less economical and pre GPF also.

In hindsight, the end of the PD series was the end of diesel AFAIC.

[Ryeman]

On 27/02/2018 at 03:27, weasley said:

 

I'm not sure that's quite right.  The EGR valve will not have to work harder, per se, just at different opening angles for different amounts of time.  It's possible that the EGR valve is being asked to operate in a previously unused portion of its range which may already be fouled.

 

SCR happens fully in the exhaust, so shouldn't impinge on EGR operation at all.  What SCR does do is allow the engine to be operated at a hotter temperature, hence being more thermally efficient, reducing PM but generating more NOx which can be caught by the SCR in the exhaust.

I was meaning that SCR limits EGR intervention by post combustion DEF injection immediately prior to the catalyst, thus allowing more efficient higher temperatures with the added benefit of reducing particulates also.

I would expect the lifespan of both to be extended, but also adding even more complexity.

[Ryeman]

Thoughts on VW’s poison pill -

https://driventowrite.com/2018/02/28/death-of-diesel-where-now-why-no-clarity/comment-page-1/#comments