EGR Cooler Problem

[snapdragon]

I have had EGR insufficient flow errors for over a year and they have got a bit more frequent. I thought I'd begin giving it a clean today and it is a pig of a job.
It has done nearly 250,000miles and so I expected it to be blocked with coke/soot.
I was using this as a guide:
http://www.vwaudiforum.co.uk/forum/showthread.php/118488-EGR-Valve/page3

I removed the upper manifold and throttle.
The throttle was a bit dirty but much cleaner than I expected
I then removed both lower manifolds (mainly to access two bolts, otherwise just the left side would do) Many items need to be removed to get to all the bolts and even then it is difficult and requires an assortment of bits.
The lower manifolds were also cleaner than I expected and then I saw from labels on them they were replaced along with the flap motors in late 2010 just before I bought the car. = Thanks to previous owner.

I removed the EGR vacuum mechanism which uses XZN socket - thankfully had a set from removing the seat to do bluetooth. Upon removing the EGR mechanism from the EGR cooler flap mechanism, I found a loose plate inside about 25mm diameter. It was just laid there and was fretted around the edge and had obviously been bouncing around. I checked all 6 intake runner flaps were intact which they were and then realised it is the EGR cooler bypass flap and it had come off the shaft and would move around and sometimes block EGR flow. It is not obvious how it was fastened to the shaft, but there are no corresponding screw-holes on the shaft for the holes in the plate, so I think it was spot-welded. I also found the shaft rather sloppy in it's bushings and this must have contributed to the flap breaking off.

So not what I expected but a new cooler bypass mechanism 059131063D (20 on diagram) is on it's way and I will strip down more on Sunday and hopefully clean and see what gaskets and screws need replacing.

[snapdragon]

Gosh 2 days of struggle to get this EGR off.

This was a big help, page 1 & 11 (photos and description) & my question at page 12.
http://www.audi-sport.net/xf/threads/my-a6-3-0tdi-avant-bit-of-a-rebuild-and-repair-thread.211351/#post2118561

I had to cut a small hose on the right of the EGR and then it should just pull off but it 'plugs' into the engine block with two metal union coolant pipes with o-rings on and these corrode to the block and get fouled with what I assume is silicate from the coolant. It took a crowbar and some rubber padding against the right cyclinder head intake face to pop it out.

Now I have it in the house and await the new part (I ordered a J suffix and have a D - and since found that is for the CABA engines not ASB, so hoping it fits - looks identical on the photos.

All the VAG EKTAmparts diagram websites seem to have gone offline which has made it harder.

I have uploaded a video that shows how much slop there is in the mechanism - the top bearing/bushing seems missing and light can even shine through and smoke has clearly been coming out as everything is black and smells of exhaust fumes. Maybe worth checking for this excessive play and soot in situ if you have this engine.

Why are all my photos upside down?

[snapdragon]

Well, it took a long time, a lots of puzzles, but the new EGR cooler bypass valve was fitted. It was £122 trade plus £75 for sundries, coolant, seals, pipes and unions etc.. also includes a new engine cover Audi emblem (£12) as the old one was lost before my ownership.

To keep the cost down, I didn't replace the seals between the lower manifolds and head and lower and upper manifolds as they were still quite deep and soft, I just cleaned them.

Now I get the engine light on and the same code as before but instead of intermittent it is every journey, but not a waste of time as the peformance is better with all that greasy soot gone, 2-3 valve ports were more than 50% blocked. I also removed that butterfly plate and stopped the smoke leaking out of the part I replaced. The EGR gas should now be cooled when it is supposed to be.
I still get the insufficient flow code but I did damage the thin vacuum pipes in several places as they had gone really brittle. I joined them together with red heatshrink tubing (see photo) and if the ends snapped off, just stuck them back into the rubber joints. I will order new ones but looks to be £90 for the set of 3.

[Pug]

Despite people not commenting, I think a lot of people have been following this thread. I have. +++

[Mechcanico Lee]

Yes I have been following it .

Snap , go into activations , active egr control and watch air mass reading drop , usually air mass reading will drop by half when egr open .

Does the 3L have swirl control is this operating ok ... again go into activations see if air mass drops when activated , swirls butterfly's normally closed at idle to get air speed up ,and open when revs over 2000 rpm or so

Egr causes so much trouble with the diesels .... manifold Black Death , ports blocked to death .....all the diesel cars I've as a power upgrade blank off egr and write out of the programs script .

Better mpg , runs better and no Black Death anymore

[snapdragon]

Cheers fellars!
I just went out to do Lee's tests and found another crack in a vacuum pipe it even snapped again when taking it off!
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So I repaired that with some lawnmower fuel tubing and went for a drive and no more engine light or code so it must have been the fact there was no vacuum.

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Lee, how do you activate EGR? If I go into output tests, the engine stops at the first test as that test is closing the throttle valve. The only way round that is to triple-click NEXT/ACTIVATE so it just does a big stumble and advances to the next test. If I get to the EGR test, I can't see the measuring blocks without closing that window down. I must be missing something.
In any case, actual EGR is alwayssignificantly more than specified...even before I started all this, maybe the VCDS labels are transposed?
Do you have any advice about how to activate EGR and view MAF?
Thanks.
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[Mechcanico Lee]

Hello snap ,most times you can just skip through like you say and get to egr and actuate it , I've always found vcds is good for activations and puts up all relevant data blocks that's involved with whatever your testing......but no worries , just put air mass data block up , remove vac pipe off egr , if you have a length of vac pipe just just put it on the egr vaccum pod and suck on it with your mouth ( oooeerrr missus ) and look for air mass drop .

Sounds like the vac leaks was the issues though if now it's not logging codes .


Where you say about actual air mass being more than desired .....is that the case now that you have sorted the vac leak to the egr .


I've found if you leave the engine idling for a time egr normally turns off ( so closed valve ) just a blip of throttle brings egr back in so then you get the lower air mass reading .

Egr switches off at idle for a process called 'smoke limitation ' ...... bleeding exhaust gases in at idle makes the combustion suffer .

Egr is an inert gas ( does not support combustion ) if you watch what egr does in data blocks when driving you will see it opens the most on lite throttle loads .

Light throttle loads makes combustion temp go high ...... high combustion temps makes NOX gases ....hence bleed in inert gas to lower burn temps ........ what happens when gas burn temps are lower ....... soot particles produced ...... hence dpfs came along .

I'm going off on a tangent here arnt i hehe

[snapdragon]

Thanks Lee
Since then, the code has come back again but no EML yet. That is how it used to be code would nearly always be there and then EML would eventually come on after a few days.

I found the other tests in Basic settings (not output tests)
The EGR would cycle on and off and I could see the EGR actual was always more than specified, and even so the EGR always seemed high as in even at it would only go down to about 280mg/St. and up to 420mg/St.

I will check the vacuum system with a vacuum tool and also block off and check the EGR valve operation and air-tightness and check valves etc....

Thanks again. Car is driving fine though and never any smoke.

[Mechcanico Lee]

Your going the correct way , vac supply to solenoids will come from brakes vac pump or on the pipe that goes to the brakes servo .... somewhere there anyhow .

With vac guage at the brakes vac pump take off point I reckon 25hg of mercury sounds good .

Trace the pipe from egr valve to the control solenoid ...... test the vac at that point , if your vac is down at that point you are loosing it somewhere ..... if its the same as the vac pump reading I would suspect the egr control solenoid is leaking the vac off .

I'm assuming here but things using vaccum ..... Egr , swirl flap control, is inlet manifold strangulation flap electric or vac control ?? Not sure but don't think it has turbo intercooler bypass ( dozer valves ) it does have egr cooler bypass so all these just need ruling out that they not loosing vaccum
Turbo vnt mechanism ..... vac or electric? .... vac system normallly have a vac resvoir aswell .

I have a superb bit of kit at work for vac leaks or boost leaks ....smoke pro machine , just smoke it up from brakes vaccum take off and it will fill the whole vac system ..... just look for the smoke .

Keep at it your close to full fix I think 👍👍



http://i618.photobucket.com/albums/tt266/mechcanicolee/Mobile%20Uploads/70C8FAAB-73E7-4225-90F0-6756B45955E2_zpsifm8jvmn.jpg (http://s618.photobucket.com/user/mechcanicolee/media/Mobile%20Uploads/70C8FAAB-73E7-4225-90F0-6756B45955E2_zpsifm8jvmn.jpg.html)

[snapdragon]

Thanks again Lee - looks a great bit of kit.

Only the EGR and cooler bypass flap are vacuum powered. The turbo VNT, intake flaps and throttle are all electric.
On 2008- models with 4 digit engine codes such as CABA, the EGR is also electric but the cooler bypass flap is still vacuum on those too.

I need to get one of those handy vac pumps - but in the meantime I found the one way checkvalve 046905291A allows air to suck and blow both ways I cleaned it out with IPA and some blackness came out but it is still not sealing inside so will order a new one.
I pulled a vacuum on the rest of the system with my oil extractor and it held pretty well but not perfect. It got dark but tomorrow I will pull a vacuum just on the cooler and watch the arm move and do the same on the EGR and see if I hear it snap shut when I pull the pipe off. It will be better when I get a handyvac with a guage.

Interestingly, with the vacuum blanked off after the brakes, I still don't get an engine light until part way through the second journey and the VCDS readings are the same EGR actual is greater than specified even though I know the EGR is shut tight and has a stiff return spring.
I have read in an SSP PDF that EGR flow is measured by lambda changes and only uses a drop in MAF reading as a fallback. My lambdas are always pegged at 99.9% as though they have been 'fixed' at that by ECU software that the previous owner did which may not help, but I had the car over 4 years before I got issues with EGR so I know it isn't the root cause.

[Mechcanico Lee]

On cars with no lamdas egr flow is measured with air mass difference only ..... it has no other way really , even if egr valve has built in tracking switch to monitor its position the real flow is measued by air mass difference .

But yes ,with lamdas it can use the difference in oxygen to monitor egr also .

Where you are getting actual egr flow more than desired is correct for your circumstance , because you have no vac to the egr the valve will be closed so egr flow will be higher

Doesn't sound right does it ....it's not measuring flow through the valve it's really measuring air mass difference , open egr lower air mass ..... closed egr more air mass .
So when you are driving on say light load ecm will be commanding egr to open let's say 35 % duty , but because there is no vac to egr it cannot open so air mass will always read as higher than actual or egr higher than actual ..... it's just the wording gets confusing as like you say how can egr be open with no vac and a strong Spring holding it back .

If you say your lamdas are fixed at 99.9 % for all the time you have had it , the ecm must be using the lack of air mass change to work out that egr is not opening thinking about it .

Does your car have dpf ?? lamdas on the diesels are very often used for regeneration control and ensuring pre dpf or oxidation cats are up there efficiency threshold as they assist in getting regen temps up .

Diagnostics is a field I enjoy doing in my job ...... specifically non intrusive diag ....pico scope , in cylinder pressure transducer waveform diag ..... something I'm just getting to grips with .

[tc4332]

You are the man Lee. Certainly in this area.
I remember being very interested the last time you started to discuss diagnosing with a scope. Waveforms are the way.

[snapdragon]

Thanks Lee.
Well... it did have a DPF when I bought it. The car was fine on a test drive and passed the documentaion and VCDS tests. It was a great price too from a used car foreourt (this was nearly 6 years ago). So I bought it and drove 120 miles home.
Over the next few days it lost more and more power until it was asthmatic and the turbo would get very hot and had started to leak exhaust gas from the gasket between the two halves (castings). I took it to Audi who said it looked like the turbo was faulty, I was annoyed and bought a new turbo and after getting a small VW indie to fit it - it was exactly the same. We scratched heads and eventually they disconnected the exhaust and went down the road and it was like a different car. They said the DPF or exhaust was - blocked but there were no warnings. They said I needed a new DPF for £1200 but I wasn't convinced as no warnings about regen, I though I will do a regen (the garage was a bit traditional and normally just does old lady's Polos etc..) and the option was greyed out in VCDS and the soot level measuring blocks were blank.

I looked more into VCDS and it said there was a flash of engine ECU 3 weeks before I bought it - it was under the Identification tab - no. of flash attempts =1 Sucessful flash attempts =1
Hmmm, it seemed like the DPF had been flashed-out in software but the DPF was still there and was now blocked. We found the pre-cat next to the turbo behind the engine had been cut in half and neatly welded back up. It looks like someone did a DPF removal but removed the pre-cat instead (as that is where the DPF is on later variants). So...they removed the soot and soot trap and everything was fine.

During the repairs, I called the seller who sounded sympathetic but the phone stopped ringing the second week. To cut a long story short they had gone bust and were struck off. Nevermind, I was still a few grand up all in all.
I don't know what software is on my ECU or who did it, whether it also gives performance boost but it has been fine for 5 years and the car now has 250,000 miles.

Aha- I think you gave me the lightbulb moment....Sounds like the measuring block 003 labels are wrong/misleading and are really MAF readings?
So 487 actual - 411 specified means 76 of EGR is being specified and the EGR should be opened until the actual MAF is brought down to match the specified MAF?
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[tc4332]

Oh Dear Snap,
My 3.0 TDI is two years older than yours and I have been a little bit into panic mode with your current saga, then I read 250K miles.
Phew, scare over, mine is under 130K so my "man maths" tells me I should be OK.
Hope that with Lee's assistance you are nearing the end.

[Mechcanico Lee]

Snap ,Sounds like you have had a bit of a hack job done to delete dpf , that's why lamdas are held at 99.9 % .

We had a sprinter van t'other month dog slow ....no codes , no reading from differential pressure sensor , I un plugged loads of sensors off the engine ....still no codes , I knew something was off , read the file with our cmd unit and sent it to my chipping man ... he said the whole fault code library has been erased !!
Complete hack job on it for dpf deletion .

If you look at air mass values you will see there the same as the egr flow data blocks , the ecm knows from its scripted algorithms that when egr duty is say 20% that the air mass should drop by a certain value , so if you have vac loss at
the egr control solenoid the egr will not open as much so air mass will not drop enough . The ecm will drive the egr solenoid to get the actual to the desired if the duty goes out of its working window egr flow codes for to high to low will be
logged .
Did you rule out all the vac loss areas .... all the splitting / cracking vac pipes replaced , if you still get the code after that I would suspect egr control solenoid

Ray
Thanks for the support , yes still playing with the scope , we have got the pico 4 channel and just got the in cylinder pressure transducer kit

For complete diagnostic nerdyness here's a Audi a2 1200 fsi engine with jumped teeth on cam chain sprocket .



http://i618.photobucket.com/albums/tt266/mechcanicolee/40CAD20B-150C-458C-A3FA-4C8D93FF4D1F_zps443ozaln.jpg (http://s618.photobucket.com/user/mechcanicolee/media/40CAD20B-150C-458C-A3FA-4C8D93FF4D1F_zps443ozaln.jpg.html)


Green trace crank sensor ( digital )
Red trace cam sensor ( Hall effect )
Blue trace cylinder pressure transducer


You are looking for correlation between the green traces missing tooth effent .... the gap in the green trace , the missing gap is the missing tooth on the flywheel that the crank sensor references from , you just have to know what a good engine trace is like to know the correlation .









http://i618.photobucket.com/albums/tt266/mechcanicolee/B1AEBC21-FE72-432C-82AB-3BA04B64CFE9_zpsloxppz83.jpg (http://s618.photobucket.com/user/mechcanicolee/media/B1AEBC21-FE72-432C-82AB-3BA04B64CFE9_zpsloxppz83.jpg.html)


Here's the fixed engine , new timing chain kit and correctly timed up

All this diagnostic capability with even taking a rocker cover off or timing cover , just done from ecm wiring plug and a spark plug hole .


Told you it's for nerds ......Anyone still here Zzzzzzzzzzz hehe !!

[tc4332]

To be honest Lee, I never thought when I was playing with scopes that they would be used like this.
I was only using them on computers, modems and early disc drives.
I admire what you are doing, just wish that I was still young enough to be involved.

[snapdragon]

Thanks Lee and TC.
I'm running with EGR disabled for now and will buy the new pipes, checkvalve and vacuum tool next month. I have spent enough on both cars and the house this month. :-( Also looking at ECU programming stuff as it might be fun to put back to normal and then make the changes myself.+++

[snapdragon]

Replaced the £56 set of vacuum pipes and check valve and light went off on it's own. Surprising how much smoother/quieter the engine is with EGR working especially on the pickup after overrun. Thanks for the assistance - until next time.

[snapdragon]

Gosh, 2.5 years ago - I forgot about this thread...
The light didn't stay off long and has kept coming back pretty much ever since. Usually at about 1600rpm with very light throttle transitioning on the overrun. In the interim, I have replaced MAF sensor, EGR vacuum valve again, EGR cooler changeover valve again, intake throttle that partially closes to increase induction, vacuum accumulator behind wheelarch and checked the system holds vacuum. I have also cleaned where the EGR gas enters the intake with oven cleaner and all inside the pipes, I noticed the flex steel pipe enters the aluminium housing on the intake and there is a sort of swirl nozzle cast into the metal - a restriction that forms the gas into a swirling jet. I cleaned that out too to no avail. The whole EGR system is now spotless and still EML comes on. It is definately working. Loads of exhaust gas came out at idlle when I opened the EGR valve with a hand vacuum pump. The only thing I need to do is test it the same way (visually see the gas) with VCDS output and see if it also works properly. If it does, it must just be that it's effect is not being registered, although I was hoping MAF sensor would satisfy that possibility.

I also filled the system with EGR cleaner that came with a long flexi straw, I filled up the EGR pipes so it flowed into the exhaust and then brushed them with the bottle brushes.

At idle, the EGR was strong enough to blow this hose out with enough force to take the plastic container with it too.

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[Mechcanico Lee]

Hello snap d , still on this one hehe ! Can you do these things ....

Get car up to temp , allow car to idle for 5 mins, egr should be closed after this idle time ( it’s called smoke limitation) with vcds have a look at air mass reading ....see if you can find the kg/h data block for the air mass reading if it’s not there the mg/st will do

Then blip throttle this will bring the egr back into play ....then read the air mass with egr active , make a note of this , and post up the excact rpm when on idle , and map sensor reading at idle in milli bar


Next , can you log boost pressure actual against boost pressure desired and try to drive it steady but under medium load for a bit on a straight bit of road , just want to see what ecm thinks of boost pressures .

[snapdragon]

How do Lee,
Thank you for your instructions.
I carried out these tests, but could not find a kg/h labelled block so used mg/s
The other thing was that in the idle test, blipping the throttle only changed the EGR duty cycle while the revs were dropping then all readings including duty cycle returned to what they were before the blip. I will try again now I have a better understading of the process though.

In the first excel document, I can where the EGR duty cycle changes over: (last column)
375.21 777 5.2 475.7 86.4 374.87 777 1 0 01 86.4 375.04 777 246.8 493.5 20.9
375.68 777 5.2 475.7 86.4 375.37 777 1 0 01 86.4 375.52 777 246.8 517 94.6

In the second file, I can see where EGR became disabled on row 120 which matches the freeze frame data of the error in the attached LOG file.

It seems as though the vacuum solenoid is very lazy. I cannot find a receipt for it, only the ebay sale of my old one (so I must have bought one). I can't remember if it was a chinese one or a used one or what, but I will take it off and see what the readings/manufacture is.

I put my vacuum pump either side of it with a T piece to use the pressure reading guage (not to pump). I found 850Hg/mm on the vacuum side and only ~150Hb/mm on the side that controls the EGR. While it does vary when doing the Basic Settings EGR ON/OFF test in Group 003, it is more of a half-hearted blip and return to 150. I will order a new Pierberg one.

I also think it has got worse, as when I used to do this test >1 year ago , there was a change in engine running/vibration between EGR ON/OFF, but only a tiny change in engine note.

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[Mechcanico Lee]

Hello I can not open some of them files on iPhone ...doesn’t matter for now

Idle air mass is about correct with air mass calculator
Vacuum on feed side of egr vac solenoid seems good .
If you look at air mass on vcds at idle ,and pull the egr valve open with your vac gun what does air mass drop down to ?

Is egr valve holding the vac ok ....not leaking down a little past diaphragm .

Was boost actual following boost desired ok on the road .

On the road on light load 30 /40 mph or so what is egr duty cycle , if you put your foot right down does egr go to a low duty cycle reading ?

Yes ,get a proper egr vac solenoid



Are the engine mountings ,electric solenoids or vacuum controlled , I’m pretty sure they are electric but some cars have vacuum types .

[snapdragon]

Thanks for the feedback Lee.
I have uploaded screenshots of the relevant parts of the log to my post above.
I will try opening the EGR with my gun when the weather is a bit better and my work shift is more sociable. I did do this and expected smoke or even stalling but not really any of either.
I did not use VCDS while I did it though.
Yes the EGR and all other parts that should - hold vacuum.
Yes boost actual vs specified is pretty good, see one of the screenshots.
Yes the EGR goes to a low duty cycle when accelerating and high on overrun 3-40mph but was disabled after just a minute of driving. MIL comes on some time later after I presume it has tried it again.

The mounts are all electric and the engine ones stopped working at <5 years old, the gearbox at ~6 years..

[snapdragon]

Just a quick update and thanks for all the help. It was the EGR vacuum solenoid 059906628B. It is one of the first things I replaced in 2017 and was GEPCO branded from Germany for 60 Euroshekels.

I remember that after replacing it the EML light went off on it's own after a couple of days which was a first and a really good sign but came on a few weeks later so it was back to the drawing board and buying more parts. If I had the vacuum tools and troubleshooting knowledge back then I probably would have diagnosed the part as faulty and returned it.

As I assumed that it did not fix the issue, I sold the old one on ebay as working. So sorry whoever go that. :tuttut:

I now have a genuine used part for £20 with a 2014 date stamp.

The morals of the story ares that replacing parts needs to be done in-hand with proper diagnosis if possible.

Cheap Chinese parts are sometimes garbage (remember the aliexpress vacuum solenoid for the EGR cooler failed too)