[Hbomb326]

My 2007 335i has been making .9 boost for the past few weeks and I’m at a loss of what the issue could be. It is currently not throwing any codes, it has an in house tune that used to be making 21 PSI with full stage 2+ modifications. Im not sure if the tune is the reason why it isnt throwing codes. I am afraid to take the tune off to find that it still doesnt throw a code since the shop charges $400 for retuning. I have had my car in a European tuning shop for the past 3 weeks and they can’t seem to find what is causing the issue.

The car currently has 135k miles. This all started when my coolant reservoir cracked and I replaced it. Alternator went shortly after this and I limped the car 2 miles to my local bmw tech for diagnosis. In retrospect I wish I had it towed. The car never overheated (to red indicator, it got to yellow) when driving it in limp mode but had all sorts of codes due to the under/overcharging alternator. These all went away after a new alternator.

Things we have tested/tried:

-Tested seals on intercooler with soap and water (no leaks)
-Smoke tested (no leaks)
-Vacuum tested (no leaks)
-Replaced boost solenoids (didn’t even throw a code with them unplugged)
-Turbos were replaced 18 months ago and are still under warranty
-Tech used a borescope to verify that both turbos are still spooling

-The tech also suggested we try a new water pump as the boost could be limited due to the car entering limp mode due to overheating but I dont want to shell out $450 for the part plus 4 hours of labor to replace the pump if its not needed. It was already replaced 45k miles ago. The car is also not showing any signs of overheating. I have tested the water pump by doing the coolant bleed and it is visually circulating.


If anyone has any advice or things to check for it would be greatly appreciated. I know it’s difficult to diagnose without any codes but it has been driven multiple miles after replacing the alternator and feeling extremely sluggish. Still no codes. I miss my car and my wallet has been taking a beating

[Mrmigs2011]

Do you have any logs you can post of how it's curre tly running? That's always a good start then we can see all running conditions of your car.

[Hbomb326]

Unfortunately I do not. I know with MHD tunes you can see performance logs but since mine is an in house tune I have no clue how to see performance logs. I have been wanting to do so for a long time. I looked into an MHD OBD2 adapter purely for logs but according to their support team the information I can extract will be limited because it is not an MHD tune. Are there any ways aside from MHD for me to record performance data? Ive considered removing my custom tune and going with MHD but idk if it is worth it just for logs

[Mrmigs2011]

Originally Posted by Hbomb326

Unfortunately I do not. I know with MHD tunes you can see performance logs but since mine is an in house tune I have no clue how to see performance logs. I have been wanting to do so for a long time. I looked into an MHD OBD2 adapter purely for logs but according to their support team the information I can extract will be limited because it is not an MHD tune. Are there any ways aside from MHD for me to record performance data? Ive considered removing my custom tune and going with MHD but idk if it is worth it just for logs

If you can get the tune files I'm sure you can flash them with mhd? Surely that would allow you log access?

You definitely need a logging software for these cars, they really can't be ran without!

I'm assuming since mhd can flash a custom map (your own) then surely logging module should work fine?

It may also be possible that the mhd tunes are better then what your currently running. Surely a tuning shop would be able to pinpoint fault if they have any credibility, and 400 for your old tune back seems a bit harsh..

[SlowE92]

Originally Posted by Hbomb326

Unfortunately I do not. I know with MHD tunes you can see performance logs but since mine is an in house tune I have no clue how to see performance logs. I have been wanting to do so for a long time. I looked into an MHD OBD2 adapter purely for logs but according to their support team the information I can extract will be limited because it is not an MHD tune. Are there any ways aside from MHD for me to record performance data? Ive considered removing my custom tune and going with MHD but idk if it is worth it just for logs

Seems sketch to charge you $400 to reflash a tune. It cost them $0 to flash a tune file to your car. Even if you get a custom tune from a vendor off here you have the flash files. My advice is to ditch them and go with a custom tune from Wedge if you're going to have to reflash your car anyways at least youll have the flash files.

[whyzee125]

Major sketch. Ditch that tune and go to stock while you diagnose and then get a reputable tuner like Wedge, V8bait, Twisted Tuning, etc. or just an OTS map which will probably still perform better than what's on there if it was running right.

[SlowE92]

Originally Posted by Hbomb326

My 2007 335i has been making .9 boost for the past few weeks and I’m at a loss of what the issue could be. It is currently not throwing any codes, it has an in house tune that used to be making 21 PSI with full stage 2+ modifications. Im not sure if the tune is the reason why it isnt throwing codes. I am afraid to take the tune off to find that it still doesnt throw a code since the shop charges $400 for retuning. I have had my car in a European tuning shop for the past 3 weeks and they can’t seem to find what is causing the issue.

The car currently has 135k miles. This all started when my coolant reservoir cracked and I replaced it. Alternator went shortly after this and I limped the car 2 miles to my local bmw tech for diagnosis. In retrospect I wish I had it towed. The car never overheated (to red indicator, it got to yellow) when driving it in limp mode but had all sorts of codes due to the under/overcharging alternator. These all went away after a new alternator.

Things we have tested/tried:

-Tested seals on intercooler with soap and water (no leaks)
-Smoke tested (no leaks)
-Vacuum tested (no leaks)
-Replaced boost solenoids (didn’t even throw a code with them unplugged)
-Turbos were replaced 18 months ago and are still under warranty
-Tech used a borescope to verify that both turbos are still spooling

-The tech also suggested we try a new water pump as the boost could be limited due to the car entering limp mode due to overheating but I dont want to shell out $450 for the part plus 4 hours of labor to replace the pump if its not needed. It was already replaced 45k miles ago. The car is also not showing any signs of overheating. I have tested the water pump by doing the coolant bleed and it is visually circulating.


If anyone has any advice or things to check for it would be greatly appreciated. I know it’s difficult to diagnose without any codes but it has been driven multiple miles after replacing the alternator and feeling extremely sluggish. Still no codes. I miss my car and my wallet has been taking a beating

And honestly if you can't find a hardware issue with the car then it is more than likely a tuning issue. If you're overheating and in limp mode then it'll definitely cut boost. On my 535xi when I started overheating due to a bad water pump it would cut boost, but it would not cycle coolant when i did the self bleeding and my temps were 280+. With MHD you can check coolant temps and oil temps and see if you're overheating. I would just shell out the money for a custom tune from someone off here or get the MHD OTS maps, and you'll have a million times more support since we can look at your logs too and you're not limited to one shop, that already cannot figure out your problem.

[Hbomb326]

Originally Posted by Mrmigs2011

If you can get the tune files I'm sure you can flash them with mhd? Surely that would allow you log access?

You definitely need a logging software for these cars, they really can't be ran without!

I'm assuming since mhd can flash a custom map (your own) then surely logging module should work fine?

It may also be possible that the mhd tunes are better then what your currently running. Surely a tuning shop would be able to pinpoint fault if they have any credibility, and 400 for your old tune back seems a bit harsh..

So I talked to the tuning shop today and they are going to send me the tune file for free. I am going to attempt to upload the custom flash through MHD that way I can record performance logs in the future. They are also willing to remove the tune for diagnosis and then put the tune back on when we get to the bottom of why it’s making .9 psi. I’m going to be getting the ultimate N54 package from MHD so hypothetically I could compare logs from my custom tune and the OTS tunes and see which one is better if I’m not mistaken.

Would I even need to upload the tune through MHD to get performance logs if it’s already on the car?

The shop also has stated that there are forms online stating that a close to failing water pump can lead to 0 boost. Does anyone know if this is true or have any references? Thank you

[Brandoch]

3.5 bar map sensor needed?

[Mrmigs2011]

Originally Posted by Hbomb326

So I talked to the tuning shop today and they are going to send me the tune file for free. I am going to attempt to upload the custom flash through MHD that way I can record performance logs in the future. They are also willing to remove the tune for diagnosis and then put the tune back on when we get to the bottom of why it’s making .9 psi. I’m going to be getting the ultimate N54 package from MHD so hypothetically I could compare logs from my custom tune and the OTS tunes and see which one is better if I’m not mistaken.

Would I even need to upload the tune through MHD to get performance logs if it’s already on the car?

The shop also has stated that there are forms online stating that a close to failing water pump can lead to 0 boost. Does anyone know if this is true or have any references? Thank you

Believe this is true of the water pump but the system would have to flag fault first before it disable the turbo'

So do a diagnostics read as well through mhd.

Test the logging module first on MHD. I wouldn't say it needs their tune to use the monitors I'm surprised that's the case, all it does is read ECU values unless mhd have had to do a ton of programming for it.

It's good the tuning shops on board, like I say you've paid the money so technically their your own tune files.

Good luck!

Make sure to upload to datazap when your done and we can try advise here.

[SlowE92]

Originally Posted by Hbomb326

So I talked to the tuning shop today and they are going to send me the tune file for free. I am going to attempt to upload the custom flash through MHD that way I can record performance logs in the future. They are also willing to remove the tune for diagnosis and then put the tune back on when we get to the bottom of why it’s making .9 psi. I’m going to be getting the ultimate N54 package from MHD so hypothetically I could compare logs from my custom tune and the OTS tunes and see which one is better if I’m not mistaken.

Would I even need to upload the tune through MHD to get performance logs if it’s already on the car?

The shop also has stated that there are forms online stating that a close to failing water pump can lead to 0 boost. Does anyone know if this is true or have any references? Thank you

The water pump would have to be flagged first before it starts cutting boost. I was able to run full boost on my 535xi with a bad water pump until my temps reached 280 and then it started cutting boost.

[lowrydr310]

You don't need a MHD tune to run the MHD logging capability. I literally just purchased a WiFi adapter and the MHD Monitor license so I can monitor and diagnose issues. I'm on a completely stock tune too, car has never been flashed before.

I'd suggest just data logging and not changing anything just yet.

If your custom tune was from any reputable shop, save your money and stick with that. Don't even mess with the MHD flasher or the OTS maps yet. Just get the monitor license and do some data logging on your current tune to see what's going on.

Also, how are you measuring 0.9psi boost? Do you have a standalone boost gauge?