HELP! 2.7t loss of power, no boost

[JeeGaa]

Hi there!

I'm having trouble with my Audi A6 C6 2,7t quattro, engine code APB.
I'm having a loss of power - really can feel that.
Tried to make boost leak test - its not holding any boost - and i noticed that boost is coming out of a occ (oil catch can) that is vented to atmosphere. So I installed boost guage its showing max. 0,3bar (very rare 0,4 for a 1/100 part of a second). So therefore I tried those steps:
1) disconected diverter valves (bypass) - no changes max 0,3bar;
2) disconected n75 cable - no changes - 0,3bar;
3) plugged off n75 pipe from turbo housing - drived very safely - boosted 0,8-0,9bar, could do even more, but didn't want to blow turbos..

F-hose is deleted, isnatlled metalic one way valve, tested on 2bar.
What to look for? Nex step I'm thinking to do cilinder compression test + change all the spark plugs.

[BasicA6]

It is possible that you could have a boost leak somewhere. I would start by checking all the connectors to the intercooler and the turbo!

[demonmk2]

have you scanned the ecu?

[JeeGaa]

I'll scan ecu tomorrow- but as i remember I had error with lambda sensors - as its straight pipe and no catalyst converters.
I have all new silicone pipes, except y-pipe. I'll post printout of vag-com, as I don't know where to look more.

[demonmk2]

car could be running in limp mode is why I asked. I suspect it is...

[MrWalker]

not familier with boost and what it should use. could it be the ignition coils. had one go out on me once while i was driving and lost a lot of power. does your CEL come on and flash while you drive?

[JeeGaa]

Ok, so I have 10 fault codes (its a lot), but basic its all about bad n75 valve (or maybe this fault is from time i plugged it off), problems with oxygen sensors and evap (its plugged off).
I will install oxygen sensor spacers so there wouldn't be any errors. No misfires.

10 Faults Found:
17538 - Fuel Trim: Bank 2 (Mult): System too Lean
P1130 - 35-00 - -
17536 - 17536/P1128/004392 - Fuel Trim; Bank 1 (Mult): System too Lean
16826 - 16826/P0442/001090 - EVAP Emission Control Sys: Small Leak
16825 - EVAP Emission Control Sys: Incorrect Flow
P0441 - 35-00 - -
17521 - Oxygen (Lambda) Sensor; B1 S1: Internal Resistance too High
17526 - Oxygen (Lambda) Sensor Heating; B1 S2: Open Circuit
17522 - Oxygen (Lambda) Sensor: B1 S2: Internal Resistance too High
P1114 - 35-00 - -
16524 - P0140/000320 - Oxygen (Lambda) Sensor B1 S2: No Activity
17539 - P1131/004401 - Oxygen/Lambda Sensor Bank 2 Sensor 1: Internal Resistance too High
17956 - Boost Pressure Regulation Valve (N75): Open Circuit
P1548 - 35-10 - - - Intermittent

[JeeGaa]

So I pressurized system starting from y-pipe - and as I said all the air is coming out of cylinder head and sump ventilation (where the oil catch can is connected, originally spider hose).
I disconnected occ and mounted small plastic bags on them - they were blowing with air!
How can boost get into sump and head? Also have bubbling sound from sump when boosting system.

[demonmk2]

its part of your evap system
your scan indicates that there is an evap leak. was it doing the same thing before you installed the catch can?
boost can escape from the evap system if there is a problem.
did you plug off the correct lines when installing it?

I would go through you sia lines and evap system. check for torn/ripped lines, loose connections. also check four cracked or busted check valves on your vacuum lines.

that first code makes me think your leak is in the sia system. it can cause boost leaks and miss fires.

[JeeGaa]

i had evap error before.
evap canister in the trunk where the spare tire is locted is cut out, also valve N80 is plugged off.





all the check valves are changed to new. What do you mean bi sia system?
I still dont get it how can all the boost get into oil system (sump,heads)? blown-by gases should bi minimum if rings in cylinders are ok.

[demonmk2]

Secondary air injection

There could be a crack or break in one of the lines

[BlackAllroad]

Have you checked to see if the N249 is plugged in and functioning correctly?

[JeeGaa]

If you mean sai - behind the cylinder heads (near the firewall) I don't have those, I got car like that from usa.
No I haven't checked N249 yet, how to tho that correctly? Its showing 27omh (i thing it should be 21 to 24omh). But will the compressed air pass in sump or cylinder heads if its broken? It connected to the vacuum reservoir right?
Maybe I'll try also to make boost test only in intake manifold - to be sure that turbos are ok or not..

Ok, so i tried to do a boost test on each side seperately - the same situation - no boost, bubbling oil sound.

[BlackAllroad]

I have no idea if the n249 could be the issue. Check this thread, I am not sure if it will fix your issues though.
http://www.audizine.com/forum/showth...les-n249-valve

[demonmk2]

is this car a manual or automatic?

and the egr's are deleted you say.

can you conferm/take pictures of how your catch can is connected.

[JeeGaa]

Car is manual, 6 speed.
You can see photo of occ upper - its connected in three locations - cylinder heads and bock/sump, f-hose is deleted.
Everything is vented to atmosphere.

Balck allroad its nut just its not boosting - its also not holding boost doing a boost test.

Here I drawed a sketch of occ. I'm also noteced that there is condansate in occ - but I thing thats becaus f-hose and panckake valves ar deleted and its not sucked back in intake.

[demonmk2]

can you smoke test it? how are you doing your pressure test? you need to do it at the throttle body hose to turbo and block off the inlet hose. all the valves are not closed when the engine is at rest so depending on how your testing its gonna pass through into the catch can.

when your driving it and trying to get into boost can you hear a loud SHHHHH noise?

[JeeGaa]

i dont have a smoke machine yet (need to build one), I test it by pressurizing Y-pipe, the I tried to check each side.
I'm testing it according to this manual:
http://www.vaglinks.com/Docs/Audi/C5...eakTesting.pdf

Well actually there is some kind of a noise SHH or like louder turbo from passenger side, maybe need to check it from bottom.
When I gutted downpipes I have checked turbos from exhaust side - no movement, no oil in exhaust.

[demonmk2]

OK, so you are going in through the y pipe......where are you blocking it off at?

noise could be intake noise, or a leak but you coulkd start you investigation in that area. maybe just a loose clamp.

[JeeGaa]

Y pipe is custom made by rs4 sizes and it has no panckake valve connection (as occ is vented to airt), so nothing to block off here.
I'm starting to get information about smoke machine, so I dont need to use soap water instead, also its pretty hard to use it underneath the car.
I would be happy if its only a clamp or pipe. I have changed all the pipes year ago amd used large clamps where space allows.

[demonmk2]

you have to block it off......usually at the throttle body boot. you can't pressure test through the engine. if your leaking its going to be in the charge pipes.

[rebelsfr3]

Literally just got past this myself. Did you check your TBB? A simple tear in mine caused all the same problems you have. Searched and searched and it was under my nose the whole time.

[JeeGaa]

Throtle body boost has new silicone pipe, tested it with soap water - no leaks at all.
I'll check charge pipes from the bottom - from turbos to intercoolers. I hope problem is there, if not I'll make boos test on TBB to ensure than from here everything is ok.

[demonmk2]

if you can smoke test it that's the best way to find the leak. IMO

[JeeGaa]

Smoke machine 90% ready, hope to test in weekend :)

[JeeGaa]

So there is bubbling oil sound and boost going out of oil catch can - cylinder heads and sump + a little bit of boost going out of n75 nipple that goes to atmosphere. 0,5bar pressure holds only for 12 seconds.
All the n80 system deleted (no check valves). still max 0,5-0,6 bar of pressure driving the car.

[Biturbo2.7t]

Hello, I have the same problem, loss of power, sound of bubbling oil max boost 0.3 bar. Have you been able to solve it, what could it be? thank you!!

[OOOOallroad]

Hello, I have the same problem, loss of power, sound of bubbling oil max boost 0.3 bar. Have you been able to solve it, what could it be? thank you!!

Sounds like it’s in limp mode. What codes are you getting?

If you can’t find a boost leak might be your n75 valve. Bubbling oil is normal sound. You should be able to pressurize to 15psi and have or drop down to zero in like 6-7 seconds I believe.

Here was an issue I was having at one point … boost gauge sensor was leaking. IMG_9952.jpg


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