[Yozh]

There are a few videos on youtube there and a few different schools of thoughts as to when to floor the accel pedal, before you turn on the ignition or after.

[Yozh]

Btw, Omaha and Mark M, concerning the low power issues that we had discussed. As you know my MAF was toast probably because I cleaned it, so I consider that unrelated, but very much contributing nonetheless. But replacing the exhaust pressure sensor did the trick. Interesting to see the behaviour of the turbine switchover, where before it would open up early and open more with the throttle, now it opens late and at lower rpm closes with more throttle input and opens gradually after 1500 rpm. I've suspected it to be the culprit as I did ran elevated pressures with plugged scr with the very first ecotune flash.

[OmahaDZL]

ITS ALIVE!!

[shnaggs]

Yay!!!

[OmahaDZL]

So in retrospect for others that run into a similar issue:

The behavior I was seeing that pointed to the change over flap/vacuum issue was that I could be driving down the interstate at 65 mph in 5th gear at 2100 rpm running perfectly fine (just an example, not sure if the mph/gear is right) and when it went to 6th, and rpm dropped to 1600, my engine bogged down completely.....started smoking...threw a code/reduced engine output.

Based on the very first post from Yozh, you can see that the engine has positional requirements for the changover flap based on RPM. Obviously rpm= exhaust output....no matter the land speed....SO DDE monitors RPM and changes the flap as the rpm rises and falls.....

The consistency of this issue, how it was ENTIRELY predictable and never varied pointed me to the changover flap and its supporting vacuum parts and electronics. It was VERY helpful to have Rheingold because I was able to go into the diagnostics and run a test that continually actuated the changover... I was able to see/feel when the car was doing what it was trying to do...I started after the solenoid (though I could have started up front to find my specific problem) and checked vacuum. (didnt even need mightyvac...finger measurement was fine.) Kept tracing up until i found vacuum in a line. Then swapped for a line I knew had vacuum and the problem was VERY evident.

EDIT: This is an important distinction that I wasnt aware of at the beginning of this process: The default position for the changover flap is for it to be open. When you start your car, vacuum builds and the flap closes...ie forces all exhaust to small turbo..........but, if things arent working and the flap is open, exhaust will be going to both the big and small turbo. When that happens at low RPM there is not enough exhaust to spool the big one and sheer volume of container is too big and you lose too much exhaust to spool the small to required boost level......so you are in an severe underboost situation. This will happen if you have the actuator disconnected entirely, there is a vacuum issue running to it or one of your pressure converters has failed. It is likely that it will behave in the manner I have described above.

Its not all that complicated when you get right down to it. i was intimidated by it for a bit because my "professional mechanics" couldnt figure it out.....but its not rocket surgery...

THANK YOU for everyones help and support on this thread....Yozh, you have been a life saver!

[shnaggs]

Wait, so just to clarify. It was the broken nipple on the vacuum canister that was the culprit?

[OmahaDZL]

Originally Posted by shnaggs

Wait, so just to clarify. It was the broken nipple on the vacuum canister that was the culprit?

Well, technically broken nipple/terrible repair job..... the vacuum reservoir was leaking terribly....thus not holding a vacuum........thus the change over valve was either not working at all...or working at an EXTREMELY reduced level.

[kydiesel35]

Nice!! Now throw that thing on a dyno!!!

[BB_cuda]

Omaha,
All the way back to early May with the cracked connectors to vacuum reservoir. Did the guys that installed the stage 3 turbos do this accidentally? Presuming yes, I would say they owe you back some labor costs if they did this and hid it.

Glad to hear you got this behind you and I'm with Ky. It's time to see what she'll do!

[OmahaDZL]

Originally Posted by BB_cuda

Omaha,
All the way back to early May with the cracked connectors to vacuum reservoir. Did the guys that installed the stage 3 turbos do this accidentally? Presuming yes, I would say they owe you back some labor costs if they did this and hid it.

Glad to hear you got this behind you and I'm with Ky. It's time to see what she'll do!

It appears yes. This was apparently an issue from the get-go. And yes my mechanics did it. No telling when the epoxy let go, but my assumption is it didnt hold for very long.

I have emailed them with my displeasure and told them that I wanted 5 hours of shop time to compensate for the last time I had it in that they once again failed to discover the issue.

Im not sure its running QUITE perfectly at the moment...I definitely once again have a small turbo....but Im still getting more smoking than I would prefer in the lower range....no codes...just a little more soot than Id like and a little bigger draw on the engine....not sure if its the adjustment rod or not....may very well be.

But it will be going on a dyno at some point...probably when it cools off a bit.

[Andrew@FixMyVW]

If you have been driving it a long time with it like that, I would reset all adaptations, it can't hurt.

[lor3n]

I have been having the same issues with my 2011 335D. I changed both pressure converters and replaced the old hoses with new silicon hoses and got a new bracket with vacuum chamber because I broke one of the nipples when removing the old hoses. I still have the intermittent lack of boost problem. I didn't change the vaccuum control valve that controls the bypass valve yet but I have the part on order. My car is up on the lift now and I'm trying to figure out how to reach in from underneath to physically move the bypass valve rod. What is the best way to see/reach in there? I am hoping the problem is the vaccuum control valve and not the bypass valve being stuck open. Also I noticed my exhaust pressure sensor looked like it was leaking, could this be causing the problem? Any insights would help.

[Yozh]

Originally Posted by lor3n

I have been having the same issues with my 2011 335D. I changed both pressure converters and replaced the old hoses with new silicon hoses and got a new bracket with vacuum chamber because I broke one of the nipples when removing the old hoses. I still have the intermittent lack of boost problem. I didn't change the vaccuum control valve that controls the bypass valve yet but I have the part on order. My car is up on the lift now and I'm trying to figure out how to reach in from underneath to physically move the bypass valve rod. What is the best way to see/reach in there? I am hoping the problem is the vaccuum control valve and not the bypass valve being stuck open. Also I noticed my exhaust pressure sensor looked like it was leaking, could this be causing the problem? Any insights would help.

Why do you need to physically move the turbo bypass actuator rod? Test the vacuum actuator? You can do it with a hand vacuum pump to see if it holds the vacuum. They do not fail too often though. Best way to reach it is to take the air box out. But to test it you have to do a bit more than that. Physically moving it will not prove anything except that your turbo switchover is not stuck. Post a picture of your exhaust pressure sensor. It is filled with a fluorosilicone lube, but why would it leak, unless someone was messing with it. They are not terribly expensive either. If you are going to get a new one, suggest getting the feed pipe as well. Those rubber portions are known to rupture with time.

[lor3n]

Originally Posted by Yozh

Why do you need to physically move the turbo bypass actuator rod? Test the vacuum actuator? You can do it with a hand vacuum pump to see if it holds the vacuum. They do not fail too often though. Best way to reach it is to take the air box out. But to test it you have to do a bit more than that. Physically moving it will not prove anything except that your turbo switchover is not stuck. Post a picture of your exhaust pressure sensor. It is filled with a fluorosilicone lube, but why would it leak, unless someone was messing with it. They are not terribly expensive either. If you are going to get a new one, suggest getting the feed pipe as well. Those rubber portions are known to rupture with time.

That makes sense, I'm no expert so when you say to see if it holds vacuum you mean to use the pump to add pressure and see if the pressure stays constant?

[OmahaDZL]

Two things......

Thing 1. Getting to all that from the top is the best...you can get to the flap itself by taking out the airbox....easy peasy. Now getting to that whole rats nest of hoses and actuators you have to take off all your plastics on top...also not terrible... Getting the back bolt out of that bracket is the worst part. However for the most part you can just swap hoses around via the maps that are on this thread a little earlier to test things out.

Thing 2. My exhaust pressure sensor burnt out JUST like that....I have it in a thread somewhere....the reason that happens is a backup of exhaust pressure (or at least so I was told)...for me, It happened because my DPF was removed and I hadnt gutted my cat yet... it wasnt completely blocked, but just enough to where the pressure would back up and force hot engine air back up into the sensor....its a direct line.....sooo...you may have some exhaust work to do......

[DozerDan82]

They REALLY pack all that stuff in there. I am in the process of pulling mine apart and it is annoying me.

Question though.

The red vacuum line, from front to back, is that supposed to hold vac? Mine does not, but if I pull vac on the front canister it goes to it holds. I can also blow air freely through the red line (front to back) I am assuming it does not do anything until it is activated?

The large canister seems to hold vac just fine and functions when the car goes 'to sleep'

I did break that vac line in messing with things so need to replace that.

I recently lost low end power (recently just got the car back running with new to me injectors, which were programmed to the comp, and a cbu cleaning.) it was running great then one day nothing.

got a code for the reducer dosing valve, cleaned that out - but it was not that bad. And for charging pressure control.

Once the car hits 2500rpm it takes off just fine, prior to that it feels like I am driving a geo metro...

[OmahaDZL]

I cant remember which line the red one is...can you go back to some earlier posts in this thread and identify the parts you are referring to?

Also...based on what you are saying, it definitely has the hallmarks of a turbo changeover flap issue.....via either the actuator, the pressure control valve or a vacuum leak/no vacuum at all. Tell me what it does when you are running fine at 2500 and you shift into a higher gear where the RPMs drop significantly. Does the engine bog down immediately?

Id definitely suggest attempting to get rheingold up and running if you have ANY issue diagnosing the issue ....if it isnt a broken nipple or something like that.

[lor3n]

Originally Posted by OmahaDZL

Thing 2. My exhaust pressure sensor burnt out JUST like that....I have it in a thread somewhere....the reason that happens is a backup of exhaust pressure (or at least so I was told)...for me, It happened because my DPF was removed and I hadnt gutted my cat yet... it wasnt completely blocked, but just enough to where the pressure would back up and force hot engine air back up into the sensor....its a direct line.....sooo...you may have some exhaust work to do......

Just to give a little background on my car… I had a DPF problem and it was basically clogged so rather than get a new one I got a Bohl Down pipe and custom mid pipe with an eBay exhaust. I got the EGR blocked off and a stage 2+ tune from BPC. I am thinking that my exhaust pressure sensor had the back pressure from when my DPF was clogged. That is the only thing that makes sense to me and it didn't influence how my car was running for the past year with the tune and deletes done.

After the year without any issues I had that dreaded lack of boost problem. I stepped on the gas and it was like the peddle went to the floor and nothing happened. I thought it was traction control because it is snowy here in Utah but I found out it wasn't traction control and that's when this educational adventure started. My dealer couldn't diagnose anything because there was no code for them to reference and their only solution was to take the turbos off and inspect them. I told them no thanks then I started reading about these issues and came across this thread. The problem was very intermittent at first and now it is almost constant. When I give it throttle at low RPM if blows a ton of smoke. After 2500 RPM it seems to have full power (I could still easily pull away from a stage 3 subaru Legacy with 350 awhp as long as I kept my RPM above 3k).

I took out the bracket and somehow managed to get that back bolt out and replaced the two pressure converters along with a new bracket. I didn't think to replace the electric changeover valve that controls the compressor bypass valve though. I didn't swap it with the one from the EGR either. BTW does the EGR electric changeover valve even need to function with the EGR blocked off and the tune?

I replaced all of the vacuum lines connected to everything on then bracket. I just got a vacuum pump so that I can test the bypass valve. I watched the videos posted in this thread about that. Should I hear a clicking noise when it opens?
I am really hoping that the problem is with the electric changeover valve and not the actual bypass valve. I am trying to figure out what my next step is and if I have missed anything major in this troubleshooting process of eliminating possible causes.

[DozerDan82]

The hose that goes to the electric changeover valve, and hose #14 in the diagram on page one. For some reason it is not letting me load the picture..

Once I am above 2500(ish) it does not care what gear it is in pulls hard.

[lor3n]

Originally Posted by DozerDan82

The hose that goes to the electric changeover valve, and hose #14 in the diagram on page one. For some reason it is not letting me load the picture..

Once I am above 2500(ish) it does not care what gear it is in pulls hard.

I think this is the hose you are referring to.

[DozerDan82]

Originally Posted by lor3n

I think this is the hose you are referring to.

Yes it is, does anyone know how it is supposed to function as far as vac/free flowing?

[OmahaDZL]

my bet is you have a nipple broken off on the back of that thing.... Im pretty sure it shouldnt be free flowing....

Also...I understand once you get above 2500 its fine...but what about when you are above 2500 and it shifts and you drop down a bunch....does the engine bog immediately? It shouldnt....once you drop down the rpms, the changeover flap should close and force a bunch of exhaust into the small turbo...

But if your flap isnt closing.....you wont have small turbo boost...and not enough exhaust to spool big turbo.....