[srey]

What I've done under the hood in the last four months:

• Aluminum Charge Pipe
• All new vaccuum lines
• New boost solenoids (generics from Amazon. I may have made a mistake)
• Checked wastegate action and ability to hold pressure (ok)
• Smoke test on the intake track multiple times (fixed small leaks here and there as they popped up. It leaks a bit from the PCV breather hose where it connects to the rear inlet)
• Pressure test with an air compressor (hooked up to the inlets. Found a small leak at the throttle body. Replaced charge pipe oring. Ok now)
• New spark plugs
• Cleaned PCV valve
• OPG
• OFHG
• Hotside intercooler coupler seal
• Coolant flush
• Oil change

Every time I do a WOT pull in 3rd, and sometimes 2nd, I hit a flat spot in the torque curve around 4000 rpm and it goes into limp mode. I say flat spot, but it seems a little choppy/surgey before it throws the code. Tonight after checking over the vacuum line system with a mityvac, checking the action of the wastegates again, and spraying the TMAP sensor and the sensor in the intake manifold with carb cleaner I decided to T into the vacuum line that bridges the two boost solenoids run it a gauge in the passenger compartment and go for a drive.

You can see what happens in the following video. I'm not convinced the solenoids are operating properly.

Here's a log of that pull.

https://datazap.me/u/chsjapanese/log...data=3-5-21-28

I'm at my wits end here. I know the vacuum system holds pressure when the car isn't running. You saw what happens when it is running. I know the wastegate actuators work and the wastegates close. I am 92.4% sure there are no leaks from the inlets to the throttle body. There is a bit of a leak where the breather hose hooks into the rear inlet, but shouldn't affect boost pressure, right? The car lags, as you can see in the log. I've been doing all this on the stock map because I want to fix the issue before going back to Stage 1. My only mods are DCI and charge pipe.

I'm almost at the point where I want to replace the boost solenoids, VANOS solenoids, TMAP sensor, and MAP sensor just in case it's one of those things. I've tried to be thorough in my diagnosing of the issue, as my past posts on the topic in the last few months indicate, but I'm starting to just guess. Hell, maybe it's a bad vacuum pump. I've never heard of one of those failing, but as long as I'm guessing...

Based on what I've written and linked does anyone have any thoughts? Thanks in advance.

[Aceway]

Have you checked the coupler that connects to the lower chargepipe?

[RocketSurgeon]

That vacuum behavior looks pretty normal to me. The wastegates usually close at a vacuum of like 12 in-HG, and you're pulling well over that.
It's odd that WGDC isn't higher when you are underboosting... Have you tried clearing adaptations?

How are you doing your boost leak test? You need to unhook the PCV vent hose from the rear inlet and cap the fitting on the turbo inlet. Absolutely don't pressurize the crankcase by leaving that connected.
On all 3 of my n54s, once the intake system was tight, I could pressurized to 5-8psi and it would probably hold for at least a solid minute.

[Bimmer_Engineer]

i hate that chime...it’s like the blue screen of death on windows 95...

[srey]

Originally Posted by Birrcrin

Have you checked the coupler that connects to the lower chargepipe?

I did and am pretty confident it's not leaking. I'll check it again with a smoke test.

[srey]

Originally Posted by RocketSurgeon

That vacuum behavior looks pretty normal to me. The wastegates usually close at a vacuum of like 12 in-HG, and you're pulling well over that.
It's odd that WGDC isn't higher when you are underboosting... Have you tried clearing adaptations?

How are you doing your boost leak test? You need to unhook the PCV vent hose from the rear inlet and cap the fitting on the turbo inlet. Absolutely don't pressurize the crankcase by leaving that connected.
On all 3 of my n54s, once the intake system was tight, I could pressurized to 5-8psi and it would probably hold for at least a solid minute.

Did you see how just prior to the chime in the video it drops below 10 and throws the code at 5 psi? It's hard to see the numbers on the gauge because i recoded it while holding my phone doing a pull on an empty country road.

I thought the relatively low wgdc was odd too. That's another reason why i suspect the off-brand boost solenoids since they control that directly (right?). I'm going to T into the vacuum lines pre canister and run the engine to see how much vacuum I'm pulling straight from the pump.

For the boost leak test i put an air hose quick connector into a 2.5" pvc cap and put it in the inlet connection where my dci normally goes and tightened the worm clamp. The other inlet was capped off. I adjusted the regulator on my air compressor to 10 psi and hooked it up to the intake system. The first time i didn't disconnect and cap off the breather hose and was praying i didn't do any damage. After that i had it disconnected. It doesn't hold pressure as long as yours. It always leaks air from the caps on the intakes. Maybe i need to seal them off better. How did you get a tight seal?

I like tinkering and troubleshooting, but at this point i just want my car to run right.

[srey]

I just tested vacuum pre cannister and post cannister/pre solenoid at idle. Pulling 25 psi, so its not the pump.

[RSL]

Problem is probably your ridiculously low ambient pressure. PID is timing out and turning off.

[srey]

Originally Posted by RSL

Problem is probably your ridiculously low ambient pressure. PID is timing out and turning off.

So what can i do about that? New map sensor assuming its a faulty reading?Im learning here, so if you can point me to a resource I'll research the hell out of it. I'm at about 4800' above sea level, btw.

[RSL]

Doesn't mean it's not VANOS or something else, but seems clear you've established there are no actual leaks and that ambient is brutally low. You can do a search for N54 PID timer.

The DME needs to account for the ambient and run more WGDC to achieve the same boost, but seems the limits it's tuned to work within aren't enough. If you logged WGDC base and WGDC after PID, you should see after PID flatline to 0 and WGDC bank 1 running at WGDC base at the error. Your bank 1 DC (final total DC) drops because all the PID (active control) turns off. It essentially can't make target boost with the PID settings it has, gives up and throws a code.

Assuming there are no other physical issues, you need a target it can reach, boost control tuning that allows more movement to reach it (more DC) or both. Custom tune is the only way to go at elevation like that and you want to do as much as you can to increase efficiency of the turbos because they'll be working much harder just to make stock boost than at sea level.

A simple bump in WGDC base should resolve the problem, but you might contact MHD or Wedge about it if you paid for map packs. They might just make the adjustments for the super low ambient pressure you've got. Otherwise, find a tuner and pay for a custom tune.

[srey]

Originally Posted by RSL

Doesn't mean it's not VANOS or something else, but seems clear you've established there are no actual leaks and that ambient is brutally low. You can do a search for N54 PID timer.

The DME needs to account for the ambient and run more WGDC to achieve the same boost, but seems the limits it's tuned to work within aren't enough. If you logged WGDC base and WGDC after PID, you should see after PID flatline to 0 and WGDC bank 1 running at WGDC base at the error. Your bank 1 DC (final total DC) drops because all the PID (active control) turns off. It essentially can't make target boost with the PID settings it has, gives up and throws a code.

Assuming there are no other physical issues, you need a target it can reach, boost control tuning that allows more movement to reach it (more DC) or both. Custom tune is the only way to go at elevation like that and you want to do as much as you can to increase efficiency of the turbos because they'll be working much harder just to make stock boost than at sea level.

A simple bump in WGDC base should resolve the problem, but you might contact MHD or Wedge about it if you paid for map packs. They might just make the adjustments for the super low ambient pressure you've got. Otherwise, find a tuner and pay for a custom tune.

Thank you! What's making me angry is that I was running a stage 1 OTS tune with MHD, then did some work on things and noticed I was getting significant timing corrections on all cylinders. I thought it might be fueling, as 91 is the best I can get here, but I flashed back to the stock tune and I've been having this issue. It doesn't matter if I flash back to stage 1 or not. It still goes into limp mode.

I wonder if replacing the sensor right before the throttle body will help. It could be a faulty reading it's sending the DME as a base. Or would that not be the case? I'll double check again for leaks anywhere. Maybe I should do the pressure test at the hot side of the intercooler instead of the inlets.

Thanks again for your help. I really appreciate it.

[RSL]

I guess the first question is where do you live/what is your elevation? If you're at sea level and it reads that low, might be a problem. If you're 5000+ feet, doubt it's misreading.

Stage 1 worked OK for boost and only started doing this after flashing back? Could just be a change in temps if they're different since. Warmer air = less dense = lower ambient pressure. What were the ambient temps/pressure like on Stage 1 of it wasn't giving 30FF?

[srey]

Elevation in the area I live/drive range from 4500'-5500' It wasn't throwing the code at first when I went stage one (Apr, avg temp 55 degrees), then started doing it. I found that the hotside intercooler coupler had popped off. I was fixing to do some other work on the car and was going to do a dyno baseline, so I flashed back to the stock map and did the work.

Ever since then it throws the code on stock or stage one maps. It's warmed up to the mid-high 70's during the day, but it threw the code last night when I took the log in my OP with ambient air temperature of 58 degrees.

[RSL]

There may be something else afoot still, but dug up a Stage 1+ log you had, it runs WGDC significantly harder than that Stage 0. You can compare that Stage 0 WGDC to the Stage 1+ WGDC and get an idea how much WGDC it needs to actually run 8-9psi compared to the WGDC you've got on Stage 0 with its 8-9psi target. You'd basically need Stage 1 boost control and Stage 0 target.

75%+ DC for 8-9psi seems like a lot, but you should find locals or other high elevation N54s with similar mods to see what they run. I don't specifically pay that much attention to high elevation data.

[335e92tx]

I think RSL just about nailed it. Depending on altitude and n54 age you might just be at the DME limits of what is tolerated.. a custom tune could prob back of the spool a bit (which seems to be where you get the FF) and still let you get less taper up top.

[srey]

Could it resolve through adaptations over time? I only have about 100 miles on the most recetly flashed tune. Also, whenever i try to reset adaptations in mhd it says the reset failed. What about a jb4 to fool the dme?

[RSL]

Adaptations won't don't do much of anything, but not sure why yours would fail when you try to reset. Ignition is on "run", but not actually running, correct? Which adaptation is failing?

The problem, or at least a big part of it, is thin air. The less dense the air, the harder compressors need to work make the same pressure because it needs much more air molecules to do so. Edit for incorrect wording: collects fewer molecules per rotation than in denser air.

There are plenty of people running 15-16psi at 5000' though, but not sure which tunes.

JB4 would make boost control easier, but no guarantee it will resolve this problem. JB4 users at elevation are chasing low boost and 30FFs too.

I'd grab a copy of TunerPro, extract a back up copy of your stock rom and try some simple changes, easiest being to lower boost target by reducing Load Target and Load Target (AT) by 5-10 across the board. Save, flash and test. That will move the target lower and closer to what it can actually make. If you're borderline between 30FF and a clean pull, that should resolve it enough to get clean logs and a better look of how it's running. Other, faster option is to just drop $$$ on a custom tune and let an experienced tuner sort it all out for your particular car in that particular environment.

[torrque]

Originally Posted by srey

Could it resolve through adaptations over time? I only have about 100 miles on the most recetly flashed tune. Also, whenever i try to reset adaptations in mhd it says the reset failed. What about a jb4 to fool the dme?

If you fail to reset adaptations, you have other problems. There is no reason why it would do that, sea level, mountain level or moon level.

Is communication to DME ok ? can you read codes with MHD? I would restart the phone/tablet, make sure you are on airplane mode and try again.

[Sgop335]

moon level lol

OP, for air density, 80F charge temp at 12.3psi ambient is like 140-150F at 14.5psi. Wow. You would think stock flash should handle that without a 30FF, though (perhaps when they are new, I guess). Something else gives in your case. a leak or old turbos.

[srey]

Originally Posted by Sgop335

moon level lol

OP, for air density, 80F charge temp at 12.3psi ambient is like 140-150F at 14.5psi. Wow. You would think stock flash should handle that without a 30FF, though (perhaps when they are new, I guess). Something else gives in your case. a leak or old turbos.

I think there must be another leak somewhere. The search continues.

[srey]

Tonight I started going over everything again. I did a boost leak test with the air compressor and didn't find anything from the hotside of the intercooler to the throttle body. I checked the function of the diverter valves; good. I checked the wastegate actuators with my hand pump, good. I went over the entire vacuum line system and didn't find anything at first. That was no surprise, as I had done it multiple times before. Then I decided to use an F connector to plug into the whole system from the two hoses going into the vacuum pump line and I got air bleeding off.

Prior I had done the lines individually, section by section with the hand pump and everything always checked out. It turns out that when I did so I was pulling the hard lines that go over the valve cover out of their mounts and then wouldn't leak. When I used the F connector I left them in their mounts and that's where I got the bleed off. I ran single pieces of vacuum hose from the pump line to the cannisters and the car builds boost and pulls again. Not perfect, but a significant amount of the problem is gone.

I tried to do a pull once the car warmed up and it still went into limp mode. I pulled over and reset adaptations on everything and it didn't come back, but I'm still getting lag. The search continues, but at least I can go WOT without going into limp mode now. Here's a log that came from auto-logging tonight.

https://datazap.me/u/chsjapanese/log...a=3-5-13-21-28

It seems like my WGDC should be higher at some points. It could be that the vacuum hoses I put in were just som 4mm washer fluid lines I had lying around. I'll order some good silicone stuff to replace it with. I also think I made a mistake buying cheaper boost solenoids to replace my originals when I was troubleshooting my 30ff. I got these ones.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

They don't quite look like what's pictured. The vent that protrudes from the top are round on the ones I got. Maybe I should order some Piermans from FCP Euro.

[srey]

Originally Posted by srey

Tonight I started going over everything again. I did a boost leak test with the air compressor and didn't find anything from the hotside of the intercooler to the throttle body. I checked the function of the diverter valves; good. I checked the wastegate actuators with my hand pump, good. I went over the entire vacuum line system and didn't find anything at first. That was no surprise, as I had done it multiple times before. Then I decided to use an F connector to plug into the whole system from the two hoses going into the vacuum pump line and I got air bleeding off.

Prior I had done the lines individually, section by section with the hand pump and everything always checked out. It turns out that when I did so I was pulling the hard lines that go over the valve cover out of their mounts and then wouldn't leak. When I used the F connector I left them in their mounts and that's where I got the bleed off. I ran single pieces of vacuum hose from the pump line to the cannisters and the car builds boost and pulls again. Not perfect, but a significant amount of the problem is gone.

I tried to do a pull once the car warmed up and it still went into limp mode. I pulled over and reset adaptations on everything and it didn't come back, but I'm still getting lag. The search continues, but at least I can go WOT without going into limp mode now. Here's a log that came from auto-logging tonight.

https://datazap.me/u/chsjapanese/log...a=3-5-13-21-28

It seems like my WGDC should be higher at some points. It could be that the vacuum hoses I put in were just som 4mm washer fluid lines I had lying around. I'll order some good silicone stuff to replace it with. I also think I made a mistake buying cheaper boost solenoids to replace my originals when I was troubleshooting my 30ff. I got these ones.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

They don't quite look like what's pictured. The vent that protrudes from the top are round on the ones I got. Maybe I should order some Piermans from FCP Euro.

NVM. Got 30FF this morning again on my morning commute. The search continues. It could be the cheap 4mm line I used to run to the canisters. It could also be the non OE/OEM boost solenoids. I'm confident that there isn't an actual leak from the outlets to the throttle body. I'll order some OEM boost solenoids and good silicone hose to see if that fixes it.

Sorry if this thread annoys anyone. I'm mostly using it to document the diagnosing process for my car.