[gclions]

Guys,

Been chasing a drivability issue for a few months now. Found what I believe is the problem.

Symptoms:
-Turbo lag
-Loss of power
-Rough idle
-Noticeably different exhaust smell
-Noticeable flutter from the intake, almost a whistle sound between 1200-1800 RPM

What I've done/replaced:
-Cleaned both upstream O2 sensors
-Cleaned MAFs twice
-Replaced air filters
-Tested vacuum, checks out okay at 27"
-Replaced both drivers side PCV hoses
-Replaced all accessible vacuum lines on top of engine
-Data logged all reasonable indications with no smoking gun

I was of the mind my upstream O2 sensors were bad, but the more I look at it they aren't crapped out. They might be sluggish, which gives me a blip in my idle, but they haven't failed outright. I cleaned them with CRC MAF cleaner, which got a bunch of carbon out of the tips. They seem to check out fine via BT cable. Next thought was the MAFs being dirty, but they appeared clean as a whistle. I had cleaned them a few weeks ago, but gave them another spray just to be sure.

I convinced myself two days ago that one or both diverter valves had failed, so I ordered two from ECS. Had a few minutes today, so I took the driver's side diverter out. This requires removing the middle turbo coolant line, which made a big mess from residual pressure. Upon inspection the plunger appeared fine, which was a bummer because I expected chips or cracks in the plunger to be my smoking gun. The plunger moved fine, smooth with no binding. So I reinstalled it.

Put everything back together, thinking the passenger side diverter might still be the culprit (it still may be, as I didn't take it apart.) Started the car to check for leaks, and low and behold there are tiny bubbles on the driver's side diverter housing. After looking closer there is a crack running pretty much the length of the housing. Good thing I sprayed coolant all over the place, because a little left over on the housing is what tipped me off. This crack lets boost escape every time the diverter opens, which is metered air, so the car runs rich.

I'm going to replace both diverters when the new ones come in, and I'll shoot a video to show anyone who is interested how to do it.

My guess is running BMS stage 2 cranked up to 3.5 finally just broke the housing, though it could have failed anyway as the thing is just black plastic. If the passenger side has the same damage this might be the weak link on these turbos though. I've looked into the Go Fast Bits DV+, which won't fit physically, though it will technically bolt up. There just isn't enough space between diverter and the adjacent turbo housing to install the DV+. The guys at GFB says it needs at least 14mm, and it's too tight for that.

Stay tuned, I'll keep you guys posted.

- Grant

[747flyboy]

Great observation. ..Well done.

[ausfahrt]

Originally Posted by gclions

Guys,

Been chasing a drivability issue for a few months now. Found what I believe is the problem.

Symptoms:
-Turbo lag
-Loss of power
-Rough idle
-Noticeably different exhaust smell
-Noticeable flutter from the intake, almost a whistle sound between 1200-1800 RPM

What I've done/replaced:
-Cleaned both upstream O2 sensors
-Cleaned MAFs twice
-Replaced air filters
-Tested vacuum, checks out okay at 27"
-Replaced both drivers side PCV hoses
-Replaced all accessible vacuum lines on top of engine
-Data logged all reasonable indications with no smoking gun

I was of the mind my upstream O2 sensors were bad, but the more I look at it they aren't crapped out. They might be sluggish, which gives me a blip in my idle, but they haven't failed outright. I cleaned them with CRC MAF cleaner, which got a bunch of carbon out of the tips. They seem to check out fine via BT cable. Next thought was the MAFs being dirty, but they appeared clean as a whistle. I had cleaned them a few weeks ago, but gave them another spray just to be sure.

I convinced myself two days ago that one or both diverter valves had failed, so I ordered two from ECS. Had a few minutes today, so I took the driver's side diverter out. This requires removing the middle turbo coolant line, which made a big mess from residual pressure. Upon inspection the plunger appeared fine, which was a bummer because I expected chips or cracks in the plunger to be my smoking gun. The plunger moved fine, smooth with no binding. So I reinstalled it.

Put everything back together, thinking the passenger side diverter might still be the culprit (it still may be, as I didn't take it apart.) Started the car to check for leaks, and low and behold there are tiny bubbles on the driver's side diverter housing. After looking closer there is a crack running pretty much the length of the housing. Good thing I sprayed coolant all over the place, because a little left over on the housing is what tipped me off. This crack lets boost escape every time the diverter opens, which is metered air, so the car runs rich.

I'm going to replace both diverters when the new ones come in, and I'll shoot a video to show anyone who is interested how to do it.

My guess is running BMS stage 2 cranked up to 3.5 finally just broke the housing, though it could have failed anyway as the thing is just black plastic. If the passenger side has the same damage this might be the weak link on these turbos though. I've looked into the Go Fast Bits DV+, which won't fit physically, though it will technically bolt up. There just isn't enough space between diverter and the adjacent turbo housing to install the DV+. The guys at GFB says it needs at least 14mm, and it's too tight for that.

Stay tuned, I'll keep you guys posted.

- Grant

I'm interested on the how to video. Thanks!

[gclions]

The diverters get here tomorrow, and I'll replace them Tuesday morning after the car has a chance to cool overnight. I'll be sure to post a video for installation.

[belal242]

Originally Posted by gclions

The diverters get here tomorrow, and I'll replace them Tuesday morning after the car has a chance to cool overnight. I'll be sure to post a video for installation.

Great job, I'll bring this up to my tech in the future.

[gclions]

Good news, I replaced the driver's side diverter valve and the car is running great. Bad news, I ended up giving up on the passenger side. I couldn't get the bottom screw out for the passenger side. I tried several different setups, but there simply isn't enough room to get to it. If I can get it loose I can definitely swap it out, but right now without something small that turns almost 180 degrees, it will require pulling the turbo to get it out. Overall, I would say the driver's side replacement was a 6/10 difficulty. That bottom screw is really tricky, though unlike the passenger side it is totally manageable.

[badblack550xi]

Great videos bro everyone should change them it's a known issue and BMW most of the time will lie that they looked at them.

[gclions]

Thanks dude, my fuel economy went from sub-12 mpg easy driving, to 18 mpg driving it hard non-stop. Big improvement, and the power has returned.

Driver's side wasn't bad, I've still got some work to do to fix the passenger side. Though, if the fishtail burn outs are any sign, I think the passenger side is still okay.

I just want people to be able to replace anything on these cars that can be done with basic hand tools. I mean, one valve alone and I saved over $600.

[535_BiTurbo]

Originally Posted by gclions

Guys,

Been chasing a drivability issue for a few months now. Found what I believe is the problem.

Symptoms:
-Turbo lag
-Loss of power
-Rough idle
-Noticeably different exhaust smell
-Noticeable flutter from the intake, almost a whistle sound between 1200-1800 RPM

What I've done/replaced:
-Cleaned both upstream O2 sensors
-Cleaned MAFs twice
-Replaced air filters
-Tested vacuum, checks out okay at 27"
-Replaced both drivers side PCV hoses
-Replaced all accessible vacuum lines on top of engine
-Data logged all reasonable indications with no smoking gun

I was of the mind my upstream O2 sensors were bad, but the more I look at it they aren't crapped out. They might be sluggish, which gives me a blip in my idle, but they haven't failed outright. I cleaned them with CRC MAF cleaner, which got a bunch of carbon out of the tips. They seem to check out fine via BT cable. Next thought was the MAFs being dirty, but they appeared clean as a whistle. I had cleaned them a few weeks ago, but gave them another spray just to be sure.

I convinced myself two days ago that one or both diverter valves had failed, so I ordered two from ECS. Had a few minutes today, so I took the driver's side diverter out. This requires removing the middle turbo coolant line, which made a big mess from residual pressure. Upon inspection the plunger appeared fine, which was a bummer because I expected chips or cracks in the plunger to be my smoking gun. The plunger moved fine, smooth with no binding. So I reinstalled it.

Put everything back together, thinking the passenger side diverter might still be the culprit (it still may be, as I didn't take it apart.) Started the car to check for leaks, and low and behold there are tiny bubbles on the driver's side diverter housing. After looking closer there is a crack running pretty much the length of the housing. Good thing I sprayed coolant all over the place, because a little left over on the housing is what tipped me off. This crack lets boost escape every time the diverter opens, which is metered air, so the car runs rich.

I'm going to replace both diverters when the new ones come in, and I'll shoot a video to show anyone who is interested how to do it.

My guess is running BMS stage 2 cranked up to 3.5 finally just broke the housing, though it could have failed anyway as the thing is just black plastic. If the passenger side has the same damage this might be the weak link on these turbos though. I've looked into the Go Fast Bits DV+, which won't fit physically, though it will technically bolt up. There just isn't enough space between diverter and the adjacent turbo housing to install the DV+. The guys at GFB says it needs at least 14mm, and it's too tight for that.

Stay tuned, I'll keep you guys posted.

- Grant

I need to check mine

[535_BiTurbo]

Mine turned out to be a severed DV/wastegate hose that runs under the alternator

[Peter528i]

.

[bmwrocky]

Great video!
Did you fix the passenger side already?
Is there any tool you can recommend for the passenger side bottom screw?

[bmwrocky]

I found this fix, they did use a different screw to solve the problem!

https://www.xbimmers.com/forums/show....php?t=1376676

Please discuss here how you solved the problem.

[ChesterCopperpot1]

Originally Posted by gclions

Thanks dude, my fuel economy went from sub-12 mpg easy driving, to 18 mpg driving it hard non-stop. Big improvement, and the power has returned.

Driver's side wasn't bad, I've still got some work to do to fix the passenger side. Though, if the fishtail burn outs are any sign, I think the passenger side is still okay.

I just want people to be able to replace anything on these cars that can be done with basic hand tools. I mean, one valve alone and I saved over $600.

I just had both diverter valves replaced in mine -- $1,400.