TDI 75 BHC with P2108 fault code Anti Shudder Valve problem

Sootywg

Member
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United-Kingdom
I would not take the butterfly off the shaft. Diesels run on full air all the time so greater chance of the screws vibrating loose and being eaten by the engine. On your gear train is there too much missing or can you relocate the meshed gears again to allow full travel? Difficult to see exactly from your picture but suspect that gear is no longer useable. Plastic gear teeth are used as a designed failure point, if the butterfly is stuck then the gear teeth get sacrificed saving the motor or mechanism. Brass gears will last longer than plastic but you have immediately remove the protection element of the sacrificial plastic teeth. Would be more inclined to fit a clean and tested used ASV provided the mounting points and physical dimensions are the same as the A2 unit.
Interesting point about stripping the gears as a safety feature, that was my concern about going for the brass replacements (however I have just ordered a set!). I have cleaned what I can and the butterfly operates smoothly without jamming, So hopefully that will not be a problem for several thousand miles. I would assume that the motor would stall if a jam occurred but that might burn the motor out.
 

Sootywg

Member
Country
United-Kingdom
Make sure you give the motor a really good clean also.
All the internals were very clean, no contamination of the electrics or motor, hence why I think it worth going down the gear replacement route. I have cancelled (I hope) my order for the brass gears having read comments about poor quality Chinese machining and have ordered these through Amazon:
Hopefully a cut above the cheaper ones on eBay. We will see.
The original gears looked to have turned to mush but when removed and cleaned it was only the pinion gear that had really worn away.
I believe I was very lucky when the EML came on, I was stuck in heavy traffic for a long time, even justifying turning the engine off until the traffic moved. The next day I started the engine to see if my cheepo OBD App could reset the EML light (it did!) but when I stopped the engine there was a load clicking noise, which I latter concluded was the gears ratcheting. I guess It would fail in the open state but if not it could have been a breakdown call out.
 

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kp 115

Member
All the internals were very clean, no contamination of the electrics or motor, hence why I think it worth going down the gear replacement route. I have cancelled (I hope) my order for the brass gears having read comments about poor quality Chinese machining and have ordered these through Amazon:
Hopefully a cut above the cheaper ones on eBay. We will see.
The original gears looked to have turned to mush but when removed and cleaned it was only the pinion gear that had really worn away.
I believe I was very lucky when the EML came on, I was stuck in heavy traffic for a long time, even justifying turning the engine off until the traffic moved. The next day I started the engine to see if my cheepo OBD App could reset the EML light (it did!) but when I stopped the engine there was a load clicking noise, which I latter concluded was the gears ratcheting. I guess It would fail in the open state but if not it could have been a breakdown call out.
Hi Sootywg,
To me the quadrant gear looks to have a buildup of debris in the root of the gear teeth I would look at removing this with a small pick tool or fine scriber whilst removing debris with a vacuum or air duster.
Hope that helps
Keith.
 

audifan

A2OC Donor
The spring under the plate I believe returns the valve to the open position and holds it there. If there was a power or gear failure the spring would reset the valve. The spring is also responsible for the wear on the gear teeth resulting in the damage you have due to the constant resistance to the gears turning add in the heat cycles and plastic ages and deteriorates. Just think every time the engine is turned off the valve shuts and reopens so over the lifetime of these cars now tens of thousand times,that is one heck of a lot of use on small parts.
 

Sootywg

Member
Country
United-Kingdom
Hi Sootywg,
To me the quadrant gear looks to have a buildup of debris in the root of the gear teeth I would look at removing this with a small pick tool or fine scriber whilst removing debris with a vacuum or air duster.
Hope that helps
Keith.
I did clean out all of the debris and whilst the black ’sector’ gear was not totally worn there was evidence of significant change to the profile of the teeth. I have now removed (destructive removal!) this ’moulded on’ gear in preparation for it’s replacement. The mating gear was so heavily worn (see earlier pic) that it has to be replaced and it would not make sense to keep one and replace the other
 

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depronman

Member
The spring under the plate I believe returns the valve to the open position and holds it there. If there was a power or gear failure the spring would reset the valve. The spring is also responsible for the wear on the gear teeth resulting in the damage you have due to the constant resistance to the gears turning add in the heat cycles and plastic ages and deteriorates. Just think every time the engine is turned off the valve shuts and reopens so over the lifetime of these cars now tens of thousand times,that is one heck of a lot of use on small parts.

If only the valve moves when you start and stop end engine it would par for ever
The issue is that this ASV flap is moving all the time in relation to throttle demand and engine load hence the wear on the gears

Paul


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Sootywg

Member
Country
United-Kingdom
If only the valve moves when you start and stop end engine it would par for ever
The issue is that this ASV flap is moving all the time in relation to throttle demand and engine load hence the wear on the gears

Paul


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Perhaps I will see a performance improvement when fixed!
I do love this group, diagnosis alone saved my who knows how much. The fix (touch wood) will be a fraction of what a garage would charge.
I think I need to up my donation!
 

depronman

Member
Perhaps I will see a performance improvement when fixed!
I do love this group, diagnosis alone saved my who knows how much. The fix (touch wood) will be a fraction of what a garage would charge.
I think I need to up my donation!

That depends on your view on egr usage
If the ASV was not moving correctly then the egr was also mot working correctly and running on less exhaust gases than Audi intended
However this is unlikely as the eml would have been on once the ecu worked out that the ASV flap was not moving as intended

If your egr is mapped out then it would make zero difference

Paul


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audifan

A2OC Donor
Hi Paul, yes I know the ASV acts like a throttle but was using the engine off to show it moving full range, but agree the wear will be more relevant in the range of movement under driving conditions.
 

Sootywg

Member
Country
United-Kingdom
Update on ASV gear replacement.
WOW that has made a difference.
I replaced the worn out gears in the ASV with the replacement gears exactly as shown in the attached video
I cleaned out the Venturi and as much as possible of the EGR valve (without removal)
After re assembly I took her for a test drive.
performance is back to what I remember after first having the re-map done.
My only concern is that the main gear seemed a lot looser on it’s spindle than the original so meshing of gears might not be as precise as intended so wear might be a problem.
Time will tell I might keep the brass repair gears that I also ordered as a possible backup.

Thanks to all the members who contributed to my education on this. It makes one even more aware of what is actually going on under the bonnet when you depress the accelerator!
 

Sootywg

Member
Country
United-Kingdom
Update on gear replacement in ASV. Having had the replacement gears installed for 2 months all was well but today the EML came on, shudder when switching off! Quick scan with ‘Torque Lite’ shows the same error code.
suspecting the new gears must have stripped I removed the ASV and dismantled (5 min job having done it more than once).
Gears look perfect but they were binding at some point in their motion, stripped, cleaned and ‘fettled’ the faces of the gears as they seemed to be rubbing and re installed. When originally fitting these gears I had read somewhere that they could bind but I thought I was OK. Not so.
So a word to anyone else fitting this type of replacement ASL gear, check all the clearance and motion as clearly manufacturing tolerances are not as per OEM.
Back on the car and seems to be working for now. If it happens again I may resort to fitting the brass gears also bought at the time.
 

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fhl

Member
Update on gear replacement in ASV. Having had the replacement gears installed for 2 months all was well but today the EML came on, shudder when switching off! Quick scan with ‘Torque Lite’ shows the same error code.
suspecting the new gears must have stripped I removed the ASV and dismantled (5 min job having done it more than once).
Gears look perfect but they were binding at some point in their motion, stripped, cleaned and ‘fettled’ the faces of the gears as they seemed to be rubbing and re installed. When originally fitting these gears I had read somewhere that they could bind but I thought I was OK. Not so.
So a word to anyone else fitting this type of replacement ASL gear, check all the clearance and motion as clearly manufacturing tolerances are not as per OEM.
Back on the car and seems to be working for now. If it happens again I may resort to fitting the brass gears also bought at the time.
That's interesting. Do you have the link to precise brass gears?

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