I've recently picked up a MkII Superb (170 CR TDI). 

 

The last owner had the emissions fix performed in 2018. Right at the very end of the 2 year warranty, they had what I believe was the common EGR failure. They weren't able to get it into a dealer due to COVID and gave up a little too easily. 

From what I know, they took it to a VAG specialist to get sorted. It was fixed as a 'don't ask, don't tell' kind of repair - they don't know what was actually done but the issue was resolved. I'm told it's passed one emissions test since.

 

I'm wanting to find what the current state of what I have is. I assume my options are..

 

• Everything is stock and it was fixed some other means. 
• EGR was cleaned/repaired.
• EGR was removed/blanked and NOT coded out.
• EGR was removed/blanked AND coded out. 
• DPF could even have possibly been removed??

 

I read I should be concerned about DPF damage if EGR has been blanked, which is why I want to find out where I stand and make sure everything is OK - as otherwise the car is in fantastic condition.

 

Any ideas on what I can do to find the current state of my EGR set up and where I should take things from here? Or should I not even worry..? Thanks!

 

 

 

What year is the car and how many miles has it done?

Not even worrying seems like a tempting approach.

EGR is about NOx reduction and NOx isn't measured in a UK MOT emissions test. 

Only if the tester can/does see that emissions equipment has been removed or modified will it fail.

 

 

6 minutes ago, Wino said:

What year is the car and how many miles has it done?

Not even worrying seems like a tempting approach.

EGR is about NOx reduction and NOx isn't measured in a UK MOT emissions test. 

Only if the tester can/does see that emissions equipment has been removed or modified will it fail.

 

 

If that’s the recommended option, I can get on board. 
My worry is less about passing emissions and more causing damage to engine/DPF (or having reduced performance and not knowing it).  
 

7 minutes ago, Wino said:

What year is the car and how many miles has it done?

Not even worrying seems like a tempting approach.

EGR is about NOx reduction and NOx isn't measured in a UK MOT emissions test. 

Only if the tester can/does see that emissions equipment has been removed or modified will it fail.

 

 

2011, 85k miles. 

You can get a bluetooth thingy that plugs in to the obd2 port and a phone app "VAG DPF" that will monitor what's going on with the DPF if you want to check that. I don't know any further details but others will.

Not having EGR functioning will surely increase the life of the DPF rather than decrease it?

 

Who told you that it would reduce the DPF life and what was their rationale?

 

Recieved wisdom is that vehicles that have had the emissions fix overwork the EGR causing its premature failure and also reduce the life of the DPF, it was on that basis that I fitted an EGR emulator/simulator to avod future problems, if I am wrong and am in fact making a problem for myself with the DPF then I would like to know so please respond.

 

There is another option missing from your list which I think may well be the case with your vehicle.

 

The broken EGR remains in place, and a blanking plate has been fitted on the pipe joint at the front of the cylinder head and an EGR emulator like mine has been fitted to make the ECU believe that the EGR's are still happening, it could also have had the emissions fix rolled back.

 

If I am correct then you will not be able to detect it via interrogating the ECU with a bluetooth dongle or VCDS as the ECU believes that the EGR system is functioning due to the falsified output of the mass airflow sensor.

 

You can detect it physically by tracing the wiring back from the MAF sensor connector, if there is a second identical sensor in line about 6" back probably hidden under the air duct then it has an emulator/simulator fitted.

Edited 23 April, 20215 yr by J.R.

Long post warning, but this is not something that can be explained in a few lines. Anyone who says otherwise doesn't know as much as they think they do.

 

Ok, so EGR & DPF are different things, doing different jobs. The emissions update can affect longevity of either but in different ways. Between some correspondence of my own with VAG in Ireland, and reading through papers from UK parliament on the matter, two things were established about the update:

1. Increased use of EGR to directly control NOx formation during the combustion process
2. Increased soot generation to allow passive reduction of NOx by oxidising soot held in the DPF

Some background on how/why this is so. NOx forms during the combustion process due to the 'burning' of atmospheric nitrogen that has been brought into the engine. The temperature and pressure present during combustion create suitable conditions for this to happen. Nitrogen and fuel are competing for oxygen during combustion.

 

In engines that run rich (more fuel than the available oxygen can consume), NOx generation is minimal as oxygen will more readily react with fuel rather than nitrogen. But this is not desirable for economy or other criterion pollutants. Also, in diesel engines, running rich makes them run hot which is undesirable as well.

 

Engines that run lean are more economical but the excess of oxygen present means conditions favour production of more NOx. DIesels have always had this problem as diesel engines are happier running lean. Modern DI petrol engines which support lean running are also vulnerable to increased NOx generation.

 

One other aspect of combustion behaviour is that regardless of how much oxygen is present, a certain gas volume is needed to ensure adequate distribution of fuel droplets and vapour so that combustion can initiate. Too close is bad as the concentration of fuel vapour between droplets won't get down below the Upper Flammability Limit and combustion won't initiate or propagate.

 

EGR helps solve this conundrum. Exhaust gas is much lower in oxygen than fresh air obviously, making it relatively inert from a combustion perspective. The trick with EGR is that it uses this inert exhaust gas to displace some fresh air from the combustion process, so now there's less excess oxygen available to form NOx, but it maintains the same gas volume in the cylinder, so there's still enough distribution of fuel in there to allow the combustion process to proceed.

 

It generally only operates at low engine loads where fuel requirement is minimal and there would otherwise be a lot of excess oxygen in the cylinder. When the load ramps up and fuel/air ratio approaches stoichiometric, EGR would cause more problems than it solves.

 

The emissions update increases EGR under low-moderate loads, which is what most of the EU test cycle is run at, but probably has changed very little at higher loads. The reason some EGRs are dying after it is that they have gotten gunked up over the life of the vehicle prior to the update, but only outside of the range of movement they would have operated within. The update commanding wider EGR opening means pushing the valve into that gunk and some of them get stuck and fail. Once replaced, a similar failure in future is unlikely, beyond the normal life expectancy of the component, as any subsequent gunking will be outside the new range of movement.

 

Now DPF. Its job is pretty self-explanatory. All DI engines (petrol or diesel) produce soot, it's an inevitable side effect of spray combustion processes. Diesels have been DI for much longer than petrols, and have until recently received the lion's share of attention when it comes to reducing/eliminating particulate emissions. (Euro 6 has brought in a requirement for particulate filters on petrols.) DPFs are a filter matrix designed to capture soot from the exhaust and hold it until a predetermined amount is stored at which point the engine shifts its operating parameters and ignites the soot to clear the filter. A small amount of ash (mostly from lubricating oil that's made it into the exhaust) gets left behind, and this eventually kills the DPF but it takes a while.

 

Now NOx comes back into the picture. Nitrous oxides are themselves pretty decent oxidisers, as evidenced by their use in a lot of rocket motors for that purpose (a bit easier to handle than liquid oxygen). Even with EGR and other combustion management strategies to minimise NOx generation during combustion, there's still some amount of it generated and this needs to be dealt with. One strategy employed to deal with this is set up the DPF so that the NOx passing through it in the exhaust gas stream oxidises some of the soot collected in it, turning it into CO2 and nitrogen. This process passively regenerates the DPF also, eliminating soot during normal engine operation. Which is what most EA189 engines in Skodas do.

 

The emissions update increased soot generation to use it as a NOx reduction measure in the DPF. It's not going to affect the amount of oil ash getting into the filter. The only way it might shorten the DPF life is due to the more frequent regens resulting in more thermal cycling, causing a failure of the filter material itself. This is more likely to be on cars that are driven on lots of short trips. Longer trips result in a lot more passive regeneration and thus fewer active regeneration cycles.

 

Could one affect the other? Yes, they're part of the same system. The whole thing has been engineered to work together as well as possible, while trying to make the best of the inevitable compromises a complex engineered system requires. It's not as simple as your mate down the pub might have you believe though.

 

To backtrack a little, the engine ECU is monitoring and controlling two core parameters: how much fuel goes in, and how much air goes in. How much air goes in is monitored by the MAF and MAP sensors. How much fuel goes in is monitored by the fuel metering system. But there's a third part to this that never gets discussed but that is nevertheless important: the lambda sensor in the exhaust. That one monitors how much oxygen remains in the exhaust leaving the engine and that data is used to control the quantity of fuel injected into the engine (in tandem with the MAF/MAP readings).

 

Why does this matter? From descriptions I'm seeing on this thread, the EGR emulators are just tweaking the MAF readings, making the engine think EGR is working normally. If we follow this through, the engine is now getting more oxygen than it realises, meaning more oxygen in the exhaust. The lambda sensor sees this and tells the engine to send more fuel. During high EGR demand driving situations this means more fuel, higher fuel consumption, maybe a bit more soot, maybe more NOx. I don't know if the ECU is set up to detect mismatch between fuel injection quantity and MAF, if it did, you could see errors down the line (I'm guessing a bit here TBH).

 

Personally, I don't think EGR defeats like this are a good idea. On modern engines with such closely coupled sub-systems running within tight margins, it's too easy to upset something without realising it until bits start to break. If you're willing to accept that possibility, feel free to go for it. You are ultimately your own warranty though: the manufacturer will not want to know about it if things break. There's always the possibility of it ultimately costing more to put right than if it had been fixed day one.

Turning to the OP's situation, it's a bit of a pain to be in the dark on it. If it's possible to talk to the previous owner, do so and find out the dealer they spoke to about the problem, and who the specialist who did the 'repair' was.

 

It's a pity the car never made it to the dealer as even if they hadn't done a repair, the diagnostic would be helpful in establishing that the fault existed and you might be able to plead a case for goodwill from Skoda. In my own case, the EGR threw its first fault code about 2 weeks after the TBM period expired in January. I contacted Skoda Ireland about it, presented them with the service history and what I knew about the update, and they offered 90 % goodwill; €100 for a new EGR was a pretty good deal I think. Bear in mind too that EGR failures were a known issue long before the emissions update came into the picture. I would say most failures have been EGRs that were going to fail anyway and the update just adjusted the timetable a bit.

 

You'll probably get more from the specialist at this point than the dealer. They should be able to tell you what they did, which is your starting point for what to do now. If the PO doesn't mind telling you, knowing how much was spent will be a useful pointer too.

 

We can assume that they didn't remove the EGR valve, since this labour is the most expensive part of the repair, and if it's out of the car, a new part is not that expensive relatively speaking. The best you could hope for would be some sort of in-situ cleaning process. These exist and can work ok if there's no damage to the moving parts of the EGR valve, and the cleaning process itself doesn't damage the EGR or other engine components. If it was cleaned and left in a functioning state you're in a good position.

 

If they have done some kind of EGR 'defeat' it's more complicated. As others have pointed out, it could just have been blanked, with or without an EGR emulator fitted. Without one, there might be some other bodge done to keep the ECU happy, or it might have been remapped. Remapped is the least awful scenario here if it was done by a competent tuner. The engine ECU is in full control of the engine with no emulators or other measures feeding modified sensor readings to the ECU to fool it into working. Worst by far is some kind of resistor pack bodge on the MAF. There's a spectrum of options between those. There's no way to 'code' out the EGR, at least not in the sense of changing ECU coding via diagnostics. It's integrated into the ECU code and needs a remap to remove/disable the functionality.

 

They are unlikely to have removed the DPF to deal with EGR problems, the two systems don't have that direct a relationship. Also, most of the labour for changing the EGR valve is that taken to drop the DPF out of the way. It'd make more sense at that point to change the EGR than start modifying things.

 

Have a dig around the MAF area for any odd looking wiring or stuff that's obviously not standard. Ditto EGR. It's not too hard to remove the pipe that introduces the EGR flow into the throttle body/intake: you could pop that off and check for blanking plates in there.

 

If all of this is making your head spin, it may be worth bringing the car to a good specialist who knows the car and the engine and get them to look over it. Someone who knows what they're looking at will spot any differences quickly enough.

Chimaera, thankyou somuch for that comprehensive posting, it has filled in all the gaps in my knowledge that I have been trying to get info on for ages.

 

You make a very good point about the Lambda value going over 1.0 and the subsequent increase in fuel delivery, I will reflect on that and the possible consequences.

 

Having scrutinised the measuring blocks for DPF parameters frequently I have come to the conclusion that whilst passive regens no doubt are effective as witnessed by the falling DPF differential pressure after a long motorway run the active regens are just as frequent, it seems, and I am quite convinced of this, that they are triggered by the calculated soot loading and not the measured soot loading.

 

My concern is that the oil ash volume/mass (VCDS keeps changing the measuring unit) is a calculated value and even if my DPF is as clean as a whistle with no pressure drop when that calculated value reaches its threshold then it will be game over for what might be a perfectly healthy and functional DPF.

 

Do you have any knowledge or opinion on this?

 

In any case my vehicle like most during the confinement is only doing shorter journeys and rarely gets an autoroute blast.

Having read the explanation from Chimaera a second time to let it further sink in I can say that had I had that knowledge before I would not have bought the EGR emulator but instead spent the money on having the "emissions fix" software rolled back.

 

Understanding now how the EGR valves get stuck when commanded beyond their restricted operating range, and also how the cheat software made the engine run on a favorable emissions map when on a rolling road there would have been the possibility for EGR failure if an owner had their car rolling road tested!!!

21 hours ago, J.R. said:

Chimaera, thankyou somuch for that comprehensive posting, it has filled in all the gaps in my knowledge that I have been trying to get info on for ages.

 

You make a very good point about the Lambda value going over 1.0 and the subsequent increase in fuel delivery, I will reflect on that and the possible consequences.

 

Having scrutinised the measuring blocks for DPF parameters frequently I have come to the conclusion that whilst passive regens no doubt are effective as witnessed by the falling DPF differential pressure after a long motorway run the active regens are just as frequent, it seems, and I am quite convinced of this, that they are triggered by the calculated soot loading and not the measured soot loading.

 

My concern is that the oil ash volume/mass (VCDS keeps changing the measuring unit) is a calculated value and even if my DPF is as clean as a whistle with no pressure drop when that calculated value reaches its threshold then it will be game over for what might be a perfectly healthy and functional DPF.

 

Do you have any knowledge or opinion on this?

 

In any case my vehicle like most during the confinement is only doing shorter journeys and rarely gets an autoroute blast.

I'm not really sure how the ECU even calculates the 'calculated' value, and why it's different to the value determined from the pressure drop across the filter. If I had to guess, it's probably some sort of integration of run time and distance covered since last regen.

 

As for which is used to trigger regen, I've been using VAG DPF for a year now and it always goes for regen at 100 % full. I'm not sure which figure contributes to that percentage right now. Conveniently, I've had the data logging option switched on, so there's lots of data there to comb over when I have a bit of time to dig through it.

On 23/04/2021 at 21:03, chimaera said:

Turning to the OP's situation, it's a bit of a pain to be in the dark on it. If it's possible to talk to the previous owner, do so and find out the dealer they spoke to about the problem, and who the specialist who did the 'repair' was.

 

It's a pity the car never made it to the dealer as even if they hadn't done a repair, the diagnostic would be helpful in establishing that the fault existed and you might be able to plead a case for goodwill from Skoda. In my own case, the EGR threw its first fault code about 2 weeks after the TBM period expired in January. I contacted Skoda Ireland about it, presented them with the service history and what I knew about the update, and they offered 90 % goodwill; €100 for a new EGR was a pretty good deal I think. Bear in mind too that EGR failures were a known issue long before the emissions update came into the picture. I would say most failures have been EGRs that were going to fail anyway and the update just adjusted the timetable a bit.

 

You'll probably get more from the specialist at this point than the dealer. They should be able to tell you what they did, which is your starting point for what to do now. If the PO doesn't mind telling you, knowing how much was spent will be a useful pointer too.

 

We can assume that they didn't remove the EGR valve, since this labour is the most expensive part of the repair, and if it's out of the car, a new part is not that expensive relatively speaking. The best you could hope for would be some sort of in-situ cleaning process. These exist and can work ok if there's no damage to the moving parts of the EGR valve, and the cleaning process itself doesn't damage the EGR or other engine components. If it was cleaned and left in a functioning state you're in a good position.

 

If they have done some kind of EGR 'defeat' it's more complicated. As others have pointed out, it could just have been blanked, with or without an EGR emulator fitted. Without one, there might be some other bodge done to keep the ECU happy, or it might have been remapped. Remapped is the least awful scenario here if it was done by a competent tuner. The engine ECU is in full control of the engine with no emulators or other measures feeding modified sensor readings to the ECU to fool it into working. Worst by far is some kind of resistor pack bodge on the MAF. There's a spectrum of options between those. There's no way to 'code' out the EGR, at least not in the sense of changing ECU coding via diagnostics. It's integrated into the ECU code and needs a remap to remove/disable the functionality.

 

They are unlikely to have removed the DPF to deal with EGR problems, the two systems don't have that direct a relationship. Also, most of the labour for changing the EGR valve is that taken to drop the DPF out of the way. It'd make more sense at that point to change the EGR than start modifying things.

 

Have a dig around the MAF area for any odd looking wiring or stuff that's obviously not standard. Ditto EGR. It's not too hard to remove the pipe that introduces the EGR flow into the throttle body/intake: you could pop that off and check for blanking plates in there.

 

If all of this is making your head spin, it may be worth bringing the car to a good specialist who knows the car and the engine and get them to look over it. Someone who knows what they're looking at will spot any differences quickly enough.

Thank you so much for your and everyone's responses. Sorry it's taken me a while to come back.

 

I do know the name of the garage that performed the works, it's a 'VAG tuning specialist' based in Falkirk - not sure of their reputation but they don't look awful! I'll get in touch with them and see what they say, if they are willing to. I'm sure it'll end up falling under GDPR or something silly like that.

*Fife, not Falkirk.