2005 1.9tdi PD BEW Bora Wagon Boost drop and shudder.

[Winning]

I had previously swaped in an egr valve i pulled from a working car. But on the sugestion of a mechanic I unpluged it. And now the shudder and boost drop have gon away. Sence i swapped the egr valve with one i cleand from a working car without this issue im suspecting it is either sticking or the wiring for it has an internal short in the wires not visable. Is there any other reason unpluging the egr valve would fix the boost drop and shudder?

 

[shoebear]

I had previously swaped in an egr valve i pulled from a working car. But on the sugestion of a mechanic I unpluged it. And now the shudder and boost drop have gon away. Sence i swapped the egr valve with one i cleand from a working car without this issue im suspecting it is either sticking or the wiring for it has an internal short in the wires not visable. Is there any other reason unpluging the egr valve would fix the boost drop and shudder?

The EGR valve is actually two valves. The EGR valve is a hole on the bottom that lets cooled exhaust gas into the intake. The Anti-Shudder Valve (ASV) is a butterfly valve which is supposed to operate briefly when shutting the engine off to help it shut off more cleanly. Of the two, the ASV is much more likely to cause the shudder symptoms you have been having. Both are operated by vacuum; the EGR valve is controlled by the large metal vacuum motor on top, and the ASV is operated by a smaller black plastic vacuum motor on the side. Which one did you unplug? Or both?

 

[Winning]

The EGR valve is actually two valves. The EGR valve is a hole on the bottom that lets cooled exhaust gas into the intake. The Anti-Shudder Valve (ASV) is a butterfly valve which is supposed to operate briefly when shutting the engine off to help it shut off more cleanly. Of the two, the ASV is much more likely to cause the shudder symptoms you have been having. Both are operated by vacuum; the EGR valve is controlled by the large metal vacuum motor on top, and the ASV is operated by a smaller black plastic vacuum motor on the side. Which one did you unplug? Or both?

Oh you are talking about on an alh or ealier tdi. Those have vaccume operated egr vlaves and shudder valves. This is a BEW tdi. So it has an electronically activated ASV and EGR valve. But you are still rite about the ASV could be the culprit or part of the issue. My suspision is the EGR valve is sticking open or not sealing properly. Leading to some boost issue. Trigering the ASV to slam shut or maybe it has stripped gears and is flapping/ slipping closed open. I just cleaned my spare EGR valve and it was sticking open from soot creaping up the stem in where the rotating arm moves it in and out. Cleaned it with a wire brush and break cleaner. Then used some engine oil and worked it back and fourth till the stem stopped sticking. This took some time and alot of wiggling. Goint to test it with 12 volts and make sure it is not sticking when moved by its own power. Then. Swap it with the one in the car. They are both peterberg brand. If the problem persists i will pull out my spare ASV and inspect it. Then swap that for the one in the car. I will post back once I have done this.

 

[shoebear]

Yes, sorry, forgot you have a BEW.

 

[Winning]

Up date. So it was not the egr or anti shudder valve i cleaned both and put them back one then the other. The shudder was still there. I then unpluged only the egr valve and the shudde went away and fuel milage improved some. This made me think whats the only part left for me to inspect. Well thats the cat so i plled the cat. I used a scope to look at the catalist from the engine side. It had lots of ash and carbon build up. I checked shining a bright light from the tail pipe side. It looked like a good portion of the cat was clogged up. I cleaned up the cat by back flushing it off of the car and soaking it over night. Using a bunch of difrent things till it looked clean and clear and the water came out clear. Now i no longer have the shudder or lack of power around 3k rpm. Also seems to build boost quicker now. I suspect the cloged cat was causing back pressure enough when the egr opened and the electronic antishudder valve tried to ajust egr flow. I suspect some over pressure or out of specified situation was occurring causing the shudder. Odd because it threw no codes. Im hoping my mpg goes back up been averaging in the low 30 mpgs.

 

[Winning]

Fixed it. Was a series of problems. Fuel tem sensor was off. But only when warmed up. Thermostat was lazy. Was a mahle or how ever you spell that. Swapped it for the vw brand thermostat and temps became better. Each one of these made the car run better. And the shudder became less. I had a spare set of stock injectors sitting in fuel. I swapped them in. Made things better and block 13 looks better. But the shudder was still there. Then i pulled the cat and scoped it lighting it from the othwr side. It was about 1/3 cloged. So i back flushed it a bunch and soaked it with several diffrent things. Untill the qater ran out clear. Then i scoped it again and it was no longer cloged up. Put it back on and the car runs much better. More exceleration and no shudder. So my thoughs are the partially clogged cat was creating back pressure that would mess with the boost pressure causing the anti shudder valve and egr to shudder cutting boost. Hope this helps any one who faces this issue.