Failing turbo?

[ekstroemtj]

Very helpful information guys. Thank you very much!

[ekstroemtj]

6 hours ago, mbagge01 said:

I agree with JFP. Check all those vacuum lines at the back of the intake manifold. Also the one line I found snapped that caused similar symptoms lewisweller is the T-connector at the very back of the engine hidden down by the firewall that connects exhaust lines from the turbos and runs to the front of the engine and connects to the crankcase ventilation. It is a very common piece that can break and be overlooked when tracking down leaks.

 

 

Picture from Lewis. 

 

We are talking about this T piece?

[mbagge01]

One other thing could possible be the check valves not functioning properly and letting boost pass by in the wrong direction.

[lewisweller]

6 hours ago, mbagge01 said:

One other thing could possible be the check valves not functioning properly and letting boost pass by in the wrong direction.

Which check valves do you refer to sir?

[tdatk]

I am suffering the same issues of building only .04 bar boost. After pulling and inspecting all the related vacuum /pressure lines, visually checking wastegate operation and both diverter valves, everything seemed ok. Still only .04b boost. I know the turbos are spinning ie;.04b on the gauge sooooooo, There are only 3 things that could be holding me back, diverter valves, change-over valve, N75 valve.....  I pulled the change-over valve and plugged the vacuum and boost feed lines. I then borrowed the check valve from the pressure line and put in series my vacuum/pressure gauge on a "T". I then pressurized the diverter valve lines with 7b air knowing the check valve would hold the pressure....it worked perfectly (see attached picture). I did a test run and  it built .08bar before popping off, but not for longer than a second.....hmmmmm, at least I knew it was capable!!!! I then decided to disconnect the wastegate line from the N75 valve and try again....total success, it pumped right up to .08 + b and stayed there. So, reflecting, I am going to replace, the N75 valve, the change-over valve and both diverter valves. I'm super happy that I confirmed the turbos were capable and the controls are just not doing what they should. Hopefully the bastard computer is not interfereing and limiting boost, if that's it I'll have to go down that road.

Anyway, here's a couple pics of how to confirm diverter valve are working.

 

Tim

[lewisweller]

1 hour ago, tdatk said:

I am suffering the same issues of building only .04 bar boost. After pulling and inspecting all the related vacuum /pressure lines, visually checking wastegate operation and both diverter valves, everything seemed ok. Still only .04b boost. I know the turbos are spinning ie;.04b on the gauge sooooooo, There are only 3 things that could be holding me back, diverter valves, change-over valve, N75 valve.....  I pulled the change-over valve and plugged the vacuum and boost feed lines. I then borrowed the check valve from the pressure line and put in series my vacuum/pressure gauge on a "T". I then pressurized the diverter valve lines with 7b air knowing the check valve would hold the pressure....it worked perfectly (see attached picture). I did a test run and  it built .08bar before popping off, but not for longer than a second.....hmmmmm, at least I knew it was capable!!!! I then decided to disconnect the wastegate line from the N75 valve and try again....total success, it pumped right up to .08 + b and stayed there. So, reflecting, I am going to replace, the N75 valve, the change-over valve and both diverter valves. I'm super happy that I confirmed the turbos were capable and the controls are just not doing what they should. Hopefully the bastard computer is not interfereing and limiting boost, if that's it I'll have to go down that road.

Anyway, here's a couple pics of how to confirm diverter valve are working.

 

Tim

Sounds like limp mode! Have you got an over boost code by any chance? 

If you disconnected the n75 valve pipe that goes to the T and then to each waste gate then drove the car it would effectively not let the wastages open, it would hold boost to the max the turbo can make and maybe trigger over boost maybe not. 

The point I'm making is, it seems as though your systems are working but your getting over boost and the dme is limiting boost by opening the divertor valves and leaking off excess boost hence 0.4bar. 

 

So check the n75 pipe from the left turbo to the bottom of the n75 valve (the boost reference pressure pipe this is, difficult to check unless you disconnected it cos it's obviously a straight through pipe the the turbo outlet) and also the n75 valve pipe that T off to each waste gate to ensure no leaks. At 7-10psi you will hear the wastages open and no escaping air noise should be heard at all. 

 

If this all checks out I have another test for the change over valve and the check valves attached to the manifold. 

 

[tdatk]

6 hours ago, lewisweller said:

Sounds like limp mode! Have you got an over boost code by any chance? 

If you disconnected the n75 valve pipe that goes to the T and then to each waste gate then drove the car it would effectively not let the wastages open, it would hold boost to the max the turbo can make and maybe trigger over boost maybe not. 

The point I'm making is, it seems as though your systems are working but your getting over boost and the dme is limiting boost by opening the divertor valves and leaking off excess boost hence 0.4bar. 

 

So check the n75 pipe from the left turbo to the bottom of the n75 valve (the boost reference pressure pipe this is, difficult to check unless you disconnected it cos it's obviously a straight through pipe the the turbo outlet) and also the n75 valve pipe that T off to each waste gate to ensure no leaks. At 7-10psi you will hear the wastages open and no escaping air noise should be heard at all. 

 

If this all checks out I have another test for the change over valve and the check valves attached to the manifold. 

 

Thanks,

 No overboost or cel's, only the issue with .04 boost. I am not ruleing out the dme interfering here as it also seem to hesitate and seems to be running rich. I don't have a durametric to see any values so I'm going by past knowledge. I have new coils, plugs and cleaned mafs and throttle plate. It's like a vacuum leak but it's not obvious. Also my vacuum tester indicates otherwise.....All the old plugs looked good but had 40k miles on them, so clean burn. What are the other change over valve tests you got?

[tdatk]

On 12/29/2016 at 9:32 PM, tdatk said:

Thanks,

 No overboost or cel's, only the issue with .04 boost. I am not ruleing out the dme interfering here as it also seem to hesitate and seems to be running rich. I don't have a durametric to see any values so I'm going by past knowledge. I have new coils, plugs and cleaned mafs and throttle plate. It's like a vacuum leak but it's not obvious. Also my vacuum tester indicates otherwise.....All the old plugs looked good but had 40k miles on them, so clean burn. What are the other change over valve tests you got?

UPDATE,

 I got a Durametric pro to see if anything was not showing up on my generic code reader.....yep....knock sensor bank 1. I am not getting any knock at all so I replaced it, same result. I got the wireing diagram and found out which wires go to each sensor to the DME. Knock voltages to the DME are whichcraft so I didn't bother to try and measure anything, I figured I'd try feeding both sensor inputs from the bank 2 knock sensor using a jumper. Worked perfectly, everything related to low boost was gone, boost and performance went through the roof compared to before and fuel mileage increased by 4 mpg highway to 18.5 mpg !!!! I will eventually replace the signal wire to the bank 1 sensor but at 185,000 miles, i'm not too worried. Thanks for your help.

[lewisweller]

1 hour ago, tdatk said:

UPDATE,

 I got a Durametric pro to see if anything was not showing up on my generic code reader.....yep....knock sensor bank 1. I am not getting any knock at all so I replaced it, same result. I got the wireing diagram and found out which wires go to each sensor to the DME. Knock voltages to the DME are whichcraft so I didn't bother to try and measure anything, I figured I'd try feeding both sensor inputs from the bank 2 knock sensor using a jumper. Worked perfectly, everything related to low boost was gone, boost and performance went through the roof compared to before and fuel mileage increased by 4 mpg highway to 18.5 mpg !!!! I will eventually replace the signal wire to the bank 1 sensor but at 185,000 miles, i'm not too worried. Thanks for your help.

Result thanks for sharing. 

I wish I had a code to follow, the misery continues.