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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKVI-A6 Golf family including Jetta SportWagen (~ 2010-2014)

VW MKVI-A6 Golf family including Jetta SportWagen (~ 2010-2014) Discussions area for A6/MkVI (2010-2014) Golf and Golf Wagons (Jetta Sportwagon in the USA).

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Old June 8th, 2018, 22:08   #1
Wilkins
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Default P047F longterm issues

I have been driving with a P047F (exhaust valve stuck open) for a little while now. I have not fixed it because I really don't miss the NOx regens and since I am planning to get the fix applied in the near future I am hoping any issues that develop as a result of ignoring the code will be resolved or covered going forward. Relying on hope isn't really rational when dealing with mechanical things so the question I have is if anyone can shed light on issues that result from operating the car longer term with the exhaust valve stuck open? Am I really running a risk of having to pay for more expensive repairs when the fix is applied? I'm not talking about the valve itself since I can pull that and free it up on the bench. I've already done it once about a year ago.

BTW the car runs great and is getting about the same mileage as my BEW. About 42 usgpm on my suburban commute (60 F) and over 45 on a couple of highway tanks not driven slowly. That is at least 2 mpg better than without the P047F.
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Old June 13th, 2018, 05:07   #2
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as long as you don't mind spitting out excess NOX, and don't need to get rid of a MIL for emissions inspection, you should be just fine.


only thing i would worry about is the error masking another issue which would otherwise be communicated by setting the MIL. might want to check the error codes every week or so.
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Old June 13th, 2018, 05:34   #3
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Some misinformation here.

"NOx regens"? Not sure what you mean there. The DPF goes through a regeneration process. The exhaust throttle flap is primarily to make the low pressure EGR flow.

The "fix" generally means the car has to be in good order beforehand, although I am not yet sure exactly what all that means, as there seems to be a lot of differing information on that front. But from what I have experienced, you will need to fix it before they fix it. I know that seems crazy.

However, the exhaust flap was under its own warranty extension prior to Dieselgate anyway.
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Old June 13th, 2018, 09:13   #4
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No misinformation here, just a little terminology drift



Self Study Program 826803
2.0 Liter TDI Common Rail
BIN5 ULEV Engine


This SSP describes a couple engine operating modes which look a little like DPF regenerations to a casual observer (since they include elevated exhaust temperatures)


DeNOX and DeSOX modes both are targeted at the NOX Storage Cat (NSC), aka NOX cat

(following quotes from the SSP)
DeNox Mode

The enhancement of the exhaust after-treatment
system with a NOx storage catalytic converter
requires the introduction of new regeneration modes
to ensure NOx conversion throughout the storage
unit’s service life.

Unlike particulate filter regeneration, a substoichiometric
exhaust gas composition is necessary
for the regeneration of the NOx storage catalytic
converter. In sub-stoichiometric operation, the
nitrogen oxides stored during the lean operation are
reduced by the exhaust enriched reduction media
consisting of HC, CO and H2.

DeSOx Mode

A further regeneration mode is provided by the
sulphur removal of the NOx storage catalytic
converter (DeSOx Mode). This is necessary as
the sulphur contained in the fuel causes sulfate
formation which slowly deactivates the NOX storage
catalytic converter.

The de-sulphurization procedure is designed for a
sulfur content of 15 ppm parts per million (ppm)
Due to the high thermal stability of the sulfates,
signifi cant levels of sulphur reduction are only
possible at temperatures above 620 C (1150 F).

The sulphur reduction procedure has been designed
so that the storage capacity of the catalytic converter
can mostly be restored without irreversible damage
to the storage material.

The sub-stoichiometric mode is very demanding in
terms of engine management. To be able to set air
mass and exhaust gas recirculation independently on
each other, two separate control circuits are used.
The air mass is set using the intake manifold throttle
valve. The exhaust recirculation rate is set using a
new, model-based regulation concept.
since the exhaust valve is used to regulate exhaust flow (and pressure), it is used to regulate the DeNOX mode. One impact of a failed exhaust flap is that the DeNOX mode does not run. since the DeNOX mode does consume fuel, the MPG does go up, at the cost of postponed NOX treatment maintenance.
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Old June 13th, 2018, 09:27   #5
meerschm
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While I am beating this horse, here is the SSP discussion of the exhaust valve:

Exhaust Throttle Valve

The exhaust throttle valve is a new component. In
the direction of exhaust flow, the Exhaust Throttle
Valve is located behind the NOx storage catalytic
converter.


There is an electric motor inside of the Exhaust
Throttle Valve that moves the throttle plate with a
gear. Adjustment of the throttle plate is infinite and
can be adapted to respective load and speed of the
engine.


The Exhaust Throttle Valve has the following tasks:
In certain operating conditions, a differential
pressure is generated between the NOx storage
catalyst and the turbocharger.
This increase in pressure helps with Low Pressure
EGR return.


Effect of Failure
If the Throttle Valve Control Module fails, the correct
regulation of exhaust gas recirculation rate is not
possible. Regeneration of the NOx storage catalyst
does not take place.
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Old June 13th, 2018, 09:29   #6
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Last time I checked, the "fix" includes a brand new NOX cat, and also a new exhaust valve, so it seems silly that they would need these working before hand.
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Old June 13th, 2018, 09:35   #7
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I agree, silly. But I have been fixing cars pretty steadily to go back for a fix, even if the component was going to be replaced anyway.

I'd have the same non-cracked DPF on four different cars now.

Then I put their cracked one back on, they run it until it fails a monitor and the MIL comes on, then they go in and get a new one.

It's nuts.

And just FYI, the self study guide's info on the deNOx catalyst's function is all bunk. If the system worked like they say it does, Dieselgate would never have happened. The whole lean NOx trap technology was a farce. They knew it. And now everyone knows it.

The tuners have got to be loving this.
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Old June 13th, 2018, 09:55   #8
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One quick question for the OP:
Have you tried to "unstick" your exhaust valve. These parts are relatively easy to remove and replace. I know people who have removed this valve and sprayed the heck out of it with penetrating oil and freed it up so it works again. This is (at best) a temporary fix but if it works, it might get you through the buyback/repair period.

Have Fun!

Don

P.S. In terms of long term issues, being stuck open is probably a lot better than being stuck shut.
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Old June 13th, 2018, 13:16   #9
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Quote:
Originally Posted by oilhammer View Post
I agree, silly. But I have been fixing cars pretty steadily to go back for a fix, even if the component was going to be replaced anyway.

I'd have the same non-cracked DPF on four different cars now.

Then I put their cracked one back on, they run it until it fails a monitor and the MIL comes on, then they go in and get a new one.

It's nuts.

And just FYI, the self study guide's info on the deNOx catalyst's function is all bunk. If the system worked like they say it does, Dieselgate would never have happened. The whole lean NOx trap technology was a farce. They knew it. And now everyone knows it.

The tuners have got to be loving this.

Seems like the SSP describes the functions. the cheat was in how they are called for and operated. So the lie is not in the SSP, it was in the net results and how these were managed.



on my car, both the deNOX and deSOX ran on cue, using fuel, and increasing temps.







we never did see any conclusion as to what the net impact would have been from running the software in the test profile long term.



remember that the post-fix version is not all that far off from the original design.



while the SSP is likely not updated, my bet is that most of the software is similar to that described in the SSP back in 2008.
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Old June 13th, 2018, 20:32   #10
Wilkins
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Thanks everyone for chiming in, especially Mike with his excerpts from the SSP. I hadn't thought of looking to see what that said. I did find the following paper which describes some of the theory behind the LNT: http://cdn.intechopen.com/pdfs/44432...rtreatment.pdf

Quite correct, I was thinking of the DeNOx mode as a regen, but different from the DPF regen. I hadn't realized there were both DeNOx and DeSOx modes. I wonder if that explains the two 'DPF' statuses 0040 and 0010? I think they are both related to the NOx catalyst and the exhaust flap. I wonder if sulfur would build-up to the point the DeSOx wouldn't restore the function? The phrasing in the SSP: "the storage capacity of the catalytic converter can mostly be restored without irreversible damage to the storage material." jumped off the page at me. I wonder if the word "mostly" is intended or is a translation from German issue?

Don - I intend to pull and try to free the exhaust valve before I take it in for the fix. It is still supposed to be covered by the warranty but I don't need an argument. I had it off and lubed two years ago as a preventative measure but I probably should have done it again last summer. I tried to loosen it up on the car but can't get it to budge - no leverage with the exhaust an inch from my face. I don't like the MIL and have checked several times to confirm no new codes have popped up. I'm procrastinating, partly because I will have to remove the 2-micron setup before the fix, just have to do it.

Oilhammer I saw a comment that one of the tuners can improve post fix driveability while improving fuel economy... I'll have to see how bad it is first.
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Old June 14th, 2018, 04:12   #11
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Quote:
Originally Posted by meerschm View Post
...

remember that the post-fix version is not all that far off from the original design.



...

That's because the original design doesn't work. It can't. The whole "lean NOx trap" idea that VAG touted, that nobody else could figure out how it works, was simply vaporware. You cannot make the diesel engine meet NOx limits prescribed now without SCR. So the "fix" just makes it a little less NOx producing, but still not able to meet the standards. It is a compromise that VAG and the EPA met. And it is a lame one at that, which is why so many people are turning to the tuners to unfix the fix, which, in many cases, actually makes the cars emit EVEN MORE NOx than they originally did when the left the factory in the first place! That's why the whole thing is a joke. And what makes it worse, in my mind, is that not only is there a bunch of fragile, expensive, hard to service parts crammed under the hood of the car, but you have to deal with it anyway. Be a totally less bitter pill to swallow if these were as tough and simple and durable as the VE and PD TDIs were (actually, ARE, since there are still hordes of those still on the road). But they are not, some would argue not even close.

If the lean NOx trap technology actually worked, all the time, and afforded these cars the ability to actually meet the NOx limits, you could shrug off a $500 repair for some sensor once in a while as a "Well, that's what they had to do to make it 'clean' "... but when you find out it was just a farce anyway, and now the way they want to "fix" it just makes it use more fuel, make more noise, make less power (some complaints, of varying degree for sure, that people have made) AND you STILL have to deal with the general fragile nature of the system AND it STILL doesn't meet the limits.....

BTW, I am in the camp that the NOx limits were (are) perhaps a bit too strict in regards to just how low everything else is, and just how little fuel these cars are capable of using. They want diesels to emit NOx levels like gassers, but is anyone forcing the gassers to emit as low of PM/HC/CO2/etc. as the diesels or make them push the same car down the road with ~30-40% less fuel? Nope.

Sorry, rant off....
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