Twin turbo help -10 vacuum no boost

[Corleone]

Ugh so anyway if this has already been posted please do forgive me new to this site and nothing showed up in a google search. anyways I have a bd5 RS-B legacy that doesn't boost at all, I thought it was the turbos so we replaced both vf31 and vf27 back to stock vf18 and vf19 when we took them off there seemed to be abit of oil in the secondary turbo and it was stiff so we assumed the secondary was buggered, after we put it back together with the new turbos took it for a drive same result hit -10 vacuum and wouldn't go past it, checked all the vacuum hoses and they seem to be in the right place not %100 sure though. Bov no longer goes off, any ideas ?

[Rosssub]

Is it idling rough? Check for a big air leak somewhere, (vac leak/boost leak). Maybe a pipe or hose leaking under the TMIC? Or split intake pipe before the primary turbo?

If it idles smooth, just wont boost. Then the exhaust or Cat might be blocked or restricted? If you shake the exhaust does anything rattle inside the mufflers or cats?

Edit:

Vacuum diagrams to double check hose routing:

http://clubsub.org.nz/forum/showthread.php?35720-B4-Vacuum-diagram

Edited May 26, 2014 by Rosssub

[Corleone]

Thanks for your reply I will recheck vacuum hoses during the day, it was idling fine but sometimes when driving and coming to a stop it starts to sputter and idle really low causing it to stall on occasion there was a vacuum hose in the wrong place and I replaced the IACV the idling is much better then what it used to be, I suspect there may be a split in the intake pipe near the primary thats the next thing I am going to try but thought I'd ask for more possible reasons, It has a decatted mid section and there doesn't seem to be any blockage in the exhaust. If there was a split somewhere would that explain the -10 boost gauge reading ?

Cheers.

[Rosssub]

If the idle is still playing up randomly, worse when warmed up. Then try a different AFM? Does the CEL ever come on? Yeah a split intake will cause lots of problems, (vac/idle/power/boost).

[Marky]

Does the throttle actually open right up

[Corleone]

CEL light will come on usually only under increased acceleration like when going from 0-100 to get onto the motorway, it idles like that randomly mostly only coming to a stop though, and yeah the throttle opens right up.

[Rosssub]

Check what fault code is stored from the CEL coming on, (diagnostics):

http://www.scoobypedia.co.uk/index.php/Knowledge/ReadingECUCodes#toc3

[Corleone]

Okay so the only stored fault code that came up was code 56 5 flashes followed by 6 short flashes. Would that contribute to the boost problem?

[Rosssub]

It must have been 6, then 5. Code 65 - differential pressure sensor. That will definitely contribute, could be vac hoses wrong, split intake pipe, dudd turbo, or just faulty sensor.

Start with the vac hose routing check, double check for air leaks (before and after turbo's).

[Corleone]

http://youtu.be/Slh7yzNwTx8

I made a recording of the error code, turbos should be sweet they came from good sources I'm gonna take it to see a subie specialist tomorrow if I rule out the vacuum lines tomorrow and will update ugggghhhhhhhh thanks again.

[Rosssub]

Sweet, good luck. Before you take it in, you can check for vacuum leaks buy spraying "engine starting fluid" (ether) around possible leak spots, (joins gaskets). If any ether gets sucked in the idle will rise.

Or block the intake at the AFM, with a jar or can. Then pump 12psi into the manifold with an air compressor. Any boost leaks you couldn't find, will hiss as they leak and be pretty obvious.

[Corleone]

I rechecked all the vacuum plumbing seems to be in order i can hear what seems like a vacuum leak when the car is idling BUT i can't pinpoint where its coming from sounds like it may be somewhere under the intake manifold on the drivers side. Going to replace the intake hose tomorrow morning would the afm contribute to negative boost ?

[Marky]

If you've got a leak between the maifold & block then that will play havoc with things to a big degree

If the AFM is playing up then it could cause problems like you describe, it might only be reading up to a certain voltage or just not right at all

It already knows there is a problem with the differential sensor - though from memory that fault can also be caused just by over or under boost, so it might just be a symptom of your problem and not the cause itself. Code 65 & 66 tend to be a "something is wrong" code not a defined one like "this thing is unplugged"

[Corleone]

I don't think the leak is between the manifold and the block somewhere in that area though, I'll look into replacing the afm after i rule out the intake hose, gonna stick it onto a computer tomorrow see what running problems might come up if all else fails I'll start piecing together a single conversion.

[Rosssub]

I had a split TT intake, right in front of the primary turbo. Pic's and replacement details in here:

http://clubsub.org.nz/forum/showthread.php?39690-BE-BH-replacement-inlet-hose-for-TT

As Marky said an air leak will play havoc with AFM/fuelling/Power. Your AFM itself could be fine, but the air leak is messing the AFM readings up.

[Corleone]

Found a split in the hose right where it connects to the primary I ripped it off and connected it back up tried to get it as air tight as possible but still sitting on negative I'll replace the whole thing tomorrow morning if I can and I'll update

[Rosssub]

Sweet, hopefully that sorts things out. Disconnect the battery while you fix it, to reset the ECU completely.

[Corleone]

So hose has been replaced STILL NO BOOST at all, took it to all subaru parts for diagnostics they rechecked all the vacuum hoses, rechecked the turbo installation and found absolutely nothing out of the ordinary gonna leave it with them overnight see if they can pin point the problem cos i've run out of ideas. ugggghhhhhhhh

[Corleone]

Okay so we have boost again it was the up pipe that was leaking thanks for all your help guys