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  1. #1
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    Sudden low boost, no boost leak, O2 sensor codes

    This morning was able to hit 22 PSI as normal and car was performing fine. After leaving work this evening, it drove fine for a few minutes but then I noticed a loud whining/ moaning sound like a boost leak when the car would try to build boost, and could not make over 3 PSI or so.*

    I have a known fouled O2 sensor i know I need to replace but been putting off for a couple months. I've been having intermittent O2 sensor faults (2C7B lambda probe behind *** con 2, signal ; 29E0 fuel mixture control ; 29E1 fuel mixture control 2) but that has not caused any low boost or other issues except I will sometimes get a Safety 5 from the bad O2 signal variance.

    When I first experienced the low boost this evening, i got new O2 sensor codes ( 2C9D Lambda probe heating in front of *** con 2, signal ; 2CA7 Lambda probe heating in front of *** con 2, function ; 2CAB Lambda probe before ***, temperature).


    When i got home I performed a boost leak test to 12 psi and no leaks. Inspected all vac lines, etc. Drove it after and still only get 2-3 psi boost and whine/ moaning is still there when attempting to build boost.

    Logs here show a short WOT hit (17_58_58) to show boost rising as normal right after leaving work. Then I got the codes above a few mins later. Then second log (18_05_28) a few mins after that, showing boost only 2-3 psi at WOT. Then a couple from tonight after boost leak test, showing low boost. (21_25_34) shows reduced boost target, and (21_25_49) shows boost target back up.*

    I am at a loss. Could a failed O2 sensor cause reduced boost? Ive read of clogged cats causing low, no boost, but this was so sudden.*

    Thanks in advance.
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    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

  2. #2
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    Also here is a log from yesterday, showing typical behavior.
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    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

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    Can you post a video of the whine/moaning?

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    I can try to take one today - but think a 'wooooooo' sound any time it tries to build boost at all. It sounds like a boost leak - however none was found on multiple tests.

    Also for context, I had the GC lites put on 4 months ago with new vac lines on that side to vac canisters, etc. Also just replaced both boost solenoids about a week ago. I checked connections to those last night.
    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

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    Stuck open wastegate?

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    What's the easiest way to check the wastegates?

    If my GC lites already have a defective wastegate, not going to be happy ...

    Would a stuck-open wastegate explain the 'wooooo' sound?
    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

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    Woooo is a very subjective sound. If you don't have a boost leak, have brand new boost solenoids and checked the vac lines to the WGs the only other option I see is stuck WG or blown turbos. I doubt the turbos are blown since it's not a screeching. Are you 100% sure the vac lines are on the WGs?

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    is there any smoke coming out of the exhaust on your car? like when you downshift and come to a stop or when you leave it in neutral/park and rev it up to 4k and let the rpms fall back down to idle?
    2008 e92 335i

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    Click here to enlarge Originally Posted by Weehe Click here to enlarge
    Woooo is a very subjective sound. If you don't have a boost leak, have brand new boost solenoids and checked the vac lines to the WGs the only other option I see is stuck WG or blown turbos. I doubt the turbos are blown since it's not a screeching. Are you 100% sure the vac lines are on the WGs?
    I know ... will try to post a video. Yes, confirmed 100% vac lines are on WGs, fully seated. Definitely no screeching sound, the noises definitely air movement, not mechanical.

    Click here to enlarge Originally Posted by Stucks Click here to enlarge
    is there any smoke coming out of the exhaust on your car? like when you downshift and come to a stop or when you leave it in neutral/park and rev it up to 4k and let the rpms fall back down to idle?
    No, i looked for smoke behind me and saw none.

    Also, have confirmed no change when running on map 0.
    Checked interxooler connections and all are solid and tight, no sign of any tears. Plus that would have shown up in the leak test, but wanted to double check.
    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

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    1 out of 1 members liked this post. Yes Reputation No
    I did some vacuum testing :


    • Vacuum to WG/Boost solenoids (Engine running,through canisters): 23" F and 22" R
    • WG/Boost Solenoid vacuum draw to WG actuators at idle: 26" F and 26" R
    • WG Actuator function: Both close with vacuum. Rear actuator I could see took 10" to fully close, and Front actuator could not see but heard it open/close.
    • WG Actuator vac hold: both hold 10-12" of vacuum with no loss of vacuum.


    I took a video of the sound the car is making:

    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

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    I'm in the process of having my setup tuned and sometimes boost will start to fall, I will get a shadow code 30ff and then can't get more than 3 psi. I have to clear dme codes and turn the car off and back on to restore boost.

    I don't have a jb4, so I don't know about it. Does it show and clear shadow codes?

    Might be worth going MHD up and pulling codes and clearing thru it.

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    I dont have 30ff code. Been reading them constantly through JB4. Have cleared them all and restarted, no effect.
    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

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    Click here to enlarge Originally Posted by LessIsMore Click here to enlarge
    I dont have 30ff code. Been reading them constantly through JB4. Have cleared them all and restarted, no effect.
    Not sure how that's possible unless you're just not in it long enough to trigger. DME is looking for 15-17psi and getting 3psi. That's ripe for 30FF.

    Maybe try setting your DWP to something a little more average for starters. Not sure what those FUA/FUD settings are for or if duty cycle is actually duty cycle on this one or torque or something else, but FF seems huge for aftermarket hybrids.

    Seems loud for the driver's side and almost sounds like a problem with air coming IN. What intake are you using?

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    Have you checked your DV/BOV to see if it is open all the time?

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    Click here to enlarge Originally Posted by LessIsMore Click here to enlarge
    I dont have 30ff code. Been reading them constantly through JB4. Have cleared them all and restarted, no effect.
    Mine showed no active codes - only the 30FF as a shadow code. I could clear it and boost would not return until I turned the car off and back on. I don't know the JB4 - does it report shadow codes as well and differentiate between them? I also don't see how you wouldn't throw a 30FF eventually.

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    Click here to enlarge Originally Posted by RSL Click here to enlarge
    Not sure how that's possible unless you're just not in it long enough to trigger. DME is looking for 15-17psi and getting 3psi. That's ripe for 30FF.

    Maybe try setting your DWP to something a little more average for starters. Not sure what those FUA/FUD settings are for or if duty cycle is actually duty cycle on this one or torque or something else, but FF seems huge for aftermarket hybrids.

    Seems loud for the driver's side and almost sounds like a problem with air coming IN. What intake are you using?
    I agree, seems like a 30ff would have shown ... Im on throttle for a good 5-10 seconds, many times at this point.

    Never had a problem with DWP but will try a lower setting, ie 50 vs 100.

    Using BMS DCI, just replaced them abt a month ago.
    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

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    1 out of 1 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by Weehe Click here to enlarge
    Have you checked your DV/BOV to see if it is open all the time?
    Just cleaned them up really well, regreased eith mobil1 synthetic. Took for test drive, but did not help at all, no change.

    I also at same time removed the recirc tubes from DVs and capped the return intake port on the inlets off, so i could better hear what the DVs are doing while driving.

    Video:


    Not sure if its clear on video, but DVs do not seem to be venting under wot.
    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

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    Click here to enlarge Originally Posted by langsbr Click here to enlarge
    Mine showed no active codes - only the 30FF as a shadow code. I could clear it and boost would not return until I turned the car off and back on. I don't know the JB4 - does it report shadow codes as well and differentiate between them? I also don't see how you wouldn't throw a 30FF eventually.
    Yes, i can see codes that are not causing a CEL. JB4 aldo stores a history of all codes ever logged. No 30FF.
    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

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    To eliminate tuning/settings as possible cause, I uninstalled JB4 completely and flashed MHD back to stock map. Put stock TMAP back on.

    Checked codes with MHD, no errors at all. (after I remembered to put the stock Tmap back on and clear the resulting 2ABD , oops!)

    No change, stil a loud wooing and inability to build boost or accelerate well. Its very slow at WOT. Still not generating any codes.

    Is the 10" actuator pressure too high?

    Started wondering what are the chances its a clogged c_talytic con_erter that just won't allow enough air through fast enough? Maybe it was dying and finally collapsed ...
    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

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    I doubt both cats collapsed at the exact same time. Triple check all of the plumbing, the intake track as well including inlets and filter.

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    We would suggest getting another person to stand alongside the car (with the hood raised) and lightly throttle (or load up/boost) the vehicle with the brake firmly pressed (so the car doesn't take off). Then listen to see where it is coming from, it is fairly loud so it should be easy to hear the area without getting too close. Also trust your helpers ability to keep the car at a standstill, obviously. If it sounds to be from the turbo area sometimes a long crowbar touched to either housing while its spooling can reveal some vibrations, to further isolate.

    First impression is that it sounds like it is a turbo about ready to let go, but doing this will at least isolate the area to or from the turbos.

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    Boost leaks can come from many many possible places. This sounds like a typical boost leak, or wastegate vacuum issue. Listening to the advice RB gives above is like punching yourself in the face. Not sure he has ever actually worked on a car after reading that.

    Bottom line, if a turbo has failed, and you have been doing these all these runs, logs, etc, etc. By this time would have a ton of smoke, and more obvious signs that you have a failed turbo. There is a very easy to separate the system into two parts. Take the lines coming from the boost cans into the solenoid, and connect them directly to the lines going to the actuators. Now drive the car VERY carefully, build boost, and be ready to lift immediately. With this done, you have NO boost control. You are applying full vacuum to the gates.

    If this fixes your problem, and you have boost again. You know the issues issue is somewhere in the wastegate control system. Lines routed wrong, bad solenoid, bad canister, etc. If this does NOT fix the problem. Then the issue is AFTER the control system. This means a boost leak ( charge pipe connection came off somewhere), stuck open wastegate, plugged cat, etc.

    Doing this simple test easily breaks the system down into two parts, and makes it easy to diagnose.

    Or you can get a crow bar, and touch it to the turbos, while punching yourself in the face. Option A will actually help you find the problem though.
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    Click here to enlarge

    All I'd add is that if you do a boost leak check, do it to at least whatever boost level you're running in your tune.

    Chris
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    1 out of 1 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by Tony@VargasTurboTech Click here to enlarge
    Boost leaks can come from many many possible places. This sounds like a typical boost leak, or wastegate vacuum issue. Listening to the advice RB gives above is like punching yourself in the face. Not sure he has ever actually worked on a car after reading that.

    Bottom line, if a turbo has failed, and you have been doing these all these runs, logs, etc, etc. By this time would have a ton of smoke, and more obvious signs that you have a failed turbo. There is a very easy to separate the system into two parts. Take the lines coming from the boost cans into the solenoid, and connect them directly to the lines going to the actuators. Now drive the car VERY carefully, build boost, and be ready to lift immediately. With this done, you have NO boost control. You are applying full vacuum to the gates.

    If this fixes your problem, and you have boost again. You know the issues issue is somewhere in the wastegate control system. Lines routed wrong, bad solenoid, bad canister, etc. If this does NOT fix the problem. Then the issue is AFTER the control system. This means a boost leak ( charge pipe connection came off somewhere), stuck open wastegate, plugged cat, etc.

    Doing this simply test easily breaks the system down into two parts, and makes it easy to diagnose.

    Or you can get a crow bar, and touch it to the turbos, while punching yourself in the face. Option A will actually help you find the problem though.
    Sorry to have offended the above vendor.

    Was simply trying to give some friendly advice based on a recent experience with a friends N20 BMW- made exact same noise and was the turbo failing (it exhibited no smoke as nothing had obliterated up to the point and bearings were obviously still standing strong) and yes it was my quick way of getting to the root of the problem. Fortunately for them BMW covered the turbo replacement under warranty. Hopefully in your case it is something simple, like a BOV or the like.

    Best of luck and once again sorry to have upset anyone.

    Rob

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    Thanks for the input, Rob and Tony. Dont have a helper available until tonight, but tried bypassing vac cans and solenoids, hooked vac lines to wg actuators directly. no change, so guess problem is after control system.

    Will have another update tonight.
    2009 535i Sport SAT -- JB4 G5 ISO |MHD E85 BEF | VTT GC Lites | VTT Inlets/Outlet |VRSF 3" DP's | VRSF 7" FMIC | Fuel-It Stage 2 | Fuel-IT TBI |BMS DCI | ER CP | Forge DV's | 4bar TMAP | Koni FSD | 15mm Rear Spacers

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