[wildey1771]

Hi Ladies & Gents,

got a 2009 335D roughly 115k on the clock.

When i bought it, it had no boost above 3k (high pressure turbo not working) after a bit of diag, replaced the pressure converter and problem was solved.
Worked for around a day and now were back to no boost past 3k. So far ive tested all the converters/solenoids and everything is working. I also changed them again for a good used set from local breakers and its still the same.

the highest reading ive seen is 2200mbar on WOT. and drops to 1300mbar after 3k. No fault codes except swirl flaps as theyre disconnected and blanked. EGR is also blanked and vac lines relating to EGR are plugged up with a bung.

All actuators are working from what i can see too.

Any past experiances or extra knowledge would be appreciated.

[Fordguy]

Have you used a gauge to verify source vacuum to both of your pressure converters? If so, what is the vacuum reading?

If it's good, move on to verifying operation of the compressor bypass valve

Using a mityvac. Hook to the canister for the bypass valve (the one down by the AC compressor). Pump it up. Using a mirror, you should see it move.

https://youtube.com/shorts/gQgjLidBCD8?feature=share

When it's resting with no vacuum. It will be in the small turbo position. When vacuum is applied, it's in the big turbo position.

If that checks out, hook a vacuum gauge to the vacuum line from the solenoid that runs this and make sure vacuum is being applied above 3,000 rpm. I just zip tied my gauge to my wiper arm for this test. Here's a video I made after repairs. Turn the volume up so you can hear what the engine is doing vs what the gauge is doing to help understand how this works

https://youtube.com/shorts/RpRSCYddS1Q?feature=share


It's possible that your issue is on this side. Either way you'll need to make sure this is working as it should be.

[lnxguy]

No boost over 3k to me indicates the turbine switchover not working or the compressor bypass. Or the associated vac lines/solenoids to them,

Also, the LP turbo is the one that makes boost above 3k, not the HP. The HP turbo is the smaller of the two

[wildey1771]

I havent managed to look at anything today but yesterday when i posted, I had low end boost and dropped at 3k.

today ive very little low end boost and occasianally picks up a bit at higher rpm but then drops it again.

a vac gague and new hose turned up today.

does anyone know which vac pipes can removed from the supply junction *under inlet*
I'd like to get the vacuum system as simplified as possible to get rid of any future issues.

Do I only need the 2 lines going towards the boost control? Can I remove and block all the others? (I know the engine mounts have some sort of vacuum but is it required)

[Fordguy]

Don't create variables by unplugging all kinds of things.

Remove the source vacuum from each of the pressure transducers, one at a time, and plug the gauge into that line. This will be the nipple in the center, not the one close to the side. Start the car up, what is your source vacuum and how long does it take to get to that number?

[wildey1771]

So The vac goes way past -20 instantly on the source lines

Today I’ve replaced the cross over solenoid and the low pressure (big turbo) solenoid and still having the same issue. Also tested the vac from the solenoids and they are giving vacuum when it should be there.

I’ve also checked the actuator on the big turbo and that does move so does cross over. Everything holds vac and moves as it should.

Still no boost past 3k

[Fordguy]

Okay, good.

You need to check the vacuum and physical operation of the compressor bypass that I outlined above, let me know what you find there. The solenoid for that is all the way at the back of the plastic frame that holds the two pressure converters.

[lnxguy]

Did you check the compressor bypass at the front of the engine underneath the vac pump? Probably a dead EV valve or line.

[wildey1771]

Had it on the ramp today. Checked all the actuators with mityvac and all are operational and not sticking.

Got a feeling I’m going to have to pull the turbos off.

What I’m not quite understanding is after replacing the big turbo solenoid everything was working for around a day and now back to this situation.

I also checked the solenoids by putting 12v to the correct wire on each solenoid and all of them seem to provide full vac at this point

[Fordguy]

You're sort of vague here. Did you specifically check the bypass, operation, vacuum integrity, and vacuum supply from the solenoid?

[wildey1771]

Hi

Sorry bud I just read what I put and it wasn’t the best explanation

So I went to all 3 actuators. High pressure low pressure and bypass. I checked them with the mityvac pump and all 3 operate as they should.

I also took one of the vacuum source lines and connected it to each actuator one at a time to make sure they operated under the cars own vac source and they did.

I also tested the solenoids by applying power to 1 of the 2 wires on each to activate them. This gives them a 100% duty cycle and gives full vac to whatever it’s connected to and all 3 solenoids actuate each actuator as it should.

I know I had 2 small boost leaks from the intercooler hoses but have replaced the seals on those two pipes with genuine bmw seals (expensive pieces of rubber)

So the vacuum system is operating as it should from what I can tell.

I saw some threads around people saying the DSC system can cause these issues and I have notice I have some faults in the dsc system. One being reduced performance or something along those lines but I can’t imagine the dsc system being the cause of this. Even fully turning off dsc doesn’t make any change.

My only faults in the dde are for my glow plugs 1-6 due to Module being dud and 429A low pressure deviation.

All vac lines are in tact also.

[Fordguy]

Thanks for the clarification!

Since it's setting the 429a code, we can rule out DSC intervention.

You said EGR is blanked, but I'm assuming DPF is still present?

It is possible that either the large turbo has a stuck open wastegate or the DPF is plugged. Best thing to do is remove the downpipe, visibly inspect the turbine, use your mityvac to supply vacuum to the wastegate and watch it's operation inside the housing. The gate is normally open and will close shut when vacuum is applied.

[wildey1771]

I will try pull the dpf tomorrow, not the next easiest job on these with removing the engine mount it’s very tight. I’ll probably gut it whilst it’s off and map it out.

It is strange as it went from normal power working fine, to this problem within a matter of hours.

I’m used to VNT turbos so this is a little different to me.

Hopefully it is the DPF as I really don’t fancy getting a set of turbos for it.

I will update on here. Hopefully this thread will help others with a similar issue that isn’t vac or solenoid related

[wildey1771]

So today I pulled the dpf out, was fairly blocked. So gutted that aswell as the cat.

Also replaced the turbo actuator (big turbo) even though it held vacuum and operated, the new actuator seemed to be a bit better with less free movement (was much stronger)

Although I had no dpf faults it seems the dpf was the issue. (The difference in the actuators wouldn’t have fixed this problem. I only did it to prevent future failure and better condition)

Fair to say the car is happy now. Boosts perfect as they should.

Thank you to everyone who has had an input. It’s greatly appreciated.

[nonford]

Good job wildey!!!! Glad you got it figured out. Just curious, ae you tuned as to the emissions portion? If so, no surprise that dpf was full of soot. Also, thanks for following up and providing the solution. So many come on here and scream of a problem and then nothing afterwards?????
I was following this, waiting to see what your dpf findings were....

[Fordguy]

Glad you got it sorted!!