# MKV N75/Boost Issue? - Read For Details



## ard978 (May 1, 2006)

i'm hoping that the following symptoms will resonate with someone and hopefully give me an idea what is wrong with my car...
CURRENT SETUP:
APR Stage 1 ECU
Upgraded PCV (Eurojet)
Upgraded DV (BSH/Forge Setup w/EvoMS Intake)
Newsouth Boost Gage split off BSH V-Twin fitting
BACKGROUND:
when i first got the APR flash everything ran great for a little while and then the car started running like crap... proceeded to replace DV and PCV and then the car ran great once again. more recently i got a CEL for misfires (cyl2 & random cyl misfire along with underboost code)... proceeded to replace all 4 coil packs (rev.A to rev.D). after clearing CELs and replacing coil packs, no more CEL in last couple hundred miles. however the following symptom remains....
CURRENT ISSUE:
the issue first became noticeable at highway speed in 5th or 6th when i would go to ~50% throttle to accelerate a little (going from ~85mph to 95mph lets say) the boost would stick at vacuum and i would have to give it way more throttle than usual and the boost would jump. i also experienced some oscillations in the boost pressure if it jumped to ~8psi it would then oscillate between 5 and 10psi. this issue has gradually become more consisten to the point now where it happens in even 1st or 2nd gear accelerating from a stop. the boost will stick anywhere from 0-4psi and i have to give it more throttle to the point where the boost finally JUMPS to 10psi or even 15psi.
i don't personally own a vagcom, but i have taken vagcom logs (unfortunately the data was only sampled at about 1/sec). also... i have a single 7min log file with a few markers following supposed events, rather than shorter logfiles covering single rpm sweeps. i recorded groups 003,114 and 116. i'm not really sure how to interpret the n75 duty cycle though...


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## crew219 (Oct 18, 2000)

Try running some different logs. Engine load vs N75 duty doesn't show much. 
I'd run N75 with block 115 to see what the requested boost is vs specified vs N75 duty cycle.
Dave


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## ard978 (May 1, 2006)

*Re: (crew219)*

i have the spec/act boost data too... but since thats from a diff group it has a diff set of timestamp data. i just used the spec/act boost timestamp data as the X for the n75 data to make the following plot.








i don't know what the two spikes up to almost 100% n75 are at 85sec and 95sec but if you look at the first two markers it looks like the n75 didn't do anything there when the boost was increasing at 50sec and 55sec... is this normal?


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## rracerguy717 (Apr 8, 2003)

*Re: (ard978)*


_Quote, originally posted by *ard978* »_
i don't know what the two spikes up to almost 100% n75 are at 85sec and 95sec but if you look at the first two markers it looks like the n75 didn't do anything there when the boost was increasing at 50sec and 55sec... is this normal?
 
Looks like something wrong with the n-75 valve IMO . Bob.G
I know there a revised n-75 like many others parts for this FSI engine LOL








p.s.
its a bitch to change, I did from underneath when i had the ko3 still in place


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## ard978 (May 1, 2006)

*Re: (rracerguy717)*

do you happen to know what the latest revision is on the n75 valve? part number?


_Modified by ard978 at 8:18 PM 1-20-2008_


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## rracerguy717 (Apr 8, 2003)

*Re: (ard978)*


_Quote, originally posted by *ard978* »_do you happen to know what the latest revision is on the n75 valve? part number?

_Modified by ard978 at 4:14 PM 1-20-2008_

The newest version n-75 that I purchased back in 4/07 was part # 06-906-283-F.







Bob.G


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## [email protected] (May 13, 2005)

*Re: (rracerguy717)*


_Quote, originally posted by *rracerguy717* »_
The newest version n-75 that I purchased back in 4/07 was part # 06-906-283-F.







Bob.G



i just bought one last week and it is still an F


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## ard978 (May 1, 2006)

*Re: ([email protected])*

well to update the situation... i had the n75 valve replaced the other day. i had a revision D on the car and it was replaced with the updated revision F. anyhow, it didn't fix the problem. the good news though is that i was beating on the car a little after the part was replaced and i finally threw a check engine light:
Friday,25,January,2008,10:57:43:05280
VAG-COM Version: Beta 711.1
Address 01: Engine
Control Module Part Number: 1K0 907 115 B
Component and/or Version: 2.0l R4/4V TFSI 0030
Software Coding: 0403010A18070160
Work Shop Code: WSC 03207
1 Fault Found:
000665 - Boost Pressure Regulation: Control Range Not Reached
P0299 - 002 - Lower Limit Exceeded - Intermittent - MIL ON
Freeze Frame:
Fault Status: 10100010
Fault Priority: 0
Fault Frequency: 6
Mileage: 58545 km
Time Indication: 0
Date: 2000.00.00
Time: 19:43:43
Freeze Frame:
RPM: 4334 /min
Load: 72.5 %
Speed: 87.0 km/h
Temperature: 91.0°C
Temperature: 0.0°C
Absolute Pres.: 1000.0 mbar
Voltage: 14.478 V
and upon looking at ross-tech's page for this code:
http://wiki.ross-tech.com/inde...00665
it has a note about the 2.0T engine:


_Quote »_Special Notes
* When found in 2.0l TFSI:
o Check Boost Pressure Control Valve (N249), for cracked rubber diaphragm. A new/optimized Valve is available, see TPL 2016331 for details. 


so first question is what is a TPL and where can i find the referenced TPL
but more importantly, does anyone know the part number and latest revision for the N249 valve? how about where it is located on the engine also?


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## crew219 (Oct 18, 2000)

N249 is the diverter valve . . . however your logs simply don't make sense because usually N75 duty cycle increases with a blown or leaky DV.
Dave


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## ard978 (May 1, 2006)

*Re: (crew219)*

well thats about the last thing in the world i wanted to hear (that n249 is diverter valve) because that means that ross-tech comment does not apply to me...
i've already replaced/upgraded the diverter valve with a somewhat custom application of a forge model (piston style rather than rubber diaphragm style)
http://www.bshspeedshop.com/st...16711

so i guess i have no idea what is causing this CEL, if anyone has any ideas...?


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## ard978 (May 1, 2006)

*Re: (ard978)*

current symptoms are basically that if i get on the gas gradually (most often in 6th but in other gears also) then i will get boost sticking at about 0-2psi even with the pedal all the way to the floor. if i then let off the gas and get back on, usually abruptly, i get the boost back (up to ~16psi) and everything is ok for the moment.


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## rbradleymedmd (Feb 24, 2007)

*Re: (ard978)*

Not an expert by any means so take this for what you want...
1. check all piping between the turbo to the TB
2. check all piping between the dv to the intake
3. maybe (note: not calling any company out here) your Forge valve isn't functioning properly
4. one of the MAF (MAP) sensors is malfunctioning
Just some thoughts that came to mind reading the thread and seeing as the n75 valve didn't change anything...


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## crew219 (Oct 18, 2000)

*Re: (ard978)*


_Quote, originally posted by *ard978* »_current symptoms are basically that if i get on the gas gradually (most often in 6th but in other gears also) then i will get boost sticking at about 0-2psi even with the pedal all the way to the floor. if i then let off the gas and get back on, usually abruptly, i get the boost back (up to ~16psi) and everything is ok for the moment.

Have you tried cleaning out the forge valve? As the valves get dirty and age, it requires significantly more vacuum to pull the valve open. From the symptoms you're describing, it sounds as if the valve may be sticking. I'm also not quite sure whether or not the valve that is used in the BSH is properly sized for the application. I don't think phil ever mentioned why he chose that valve over the standard Forge 007.
Dave


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## ard978 (May 1, 2006)

*Re: (crew219)*

thanks for the ideas, i am definitely going to open up the forge valve and i will check connections while i'm at it


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## rbradleymedmd (Feb 24, 2007)

*Re: (ard978)*

may as well pick up a MAF sensor cleaner just to rule that it's not just dirty...just in case...plus it's a good thing to keep around


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## NEW2B (Dec 1, 2006)

*Re: (rbradleymedmd)*

did you fix this?


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## unclespoon (Jan 31, 2004)

*Re: (ard978)*


_Quote, originally posted by *ard978* »_current symptoms are basically that if i get on the gas gradually (most often in 6th but in other gears also) then i will get boost sticking at about 0-2psi even with the pedal all the way to the floor. if i then let off the gas and get back on, usually abruptly, i get the boost back (up to ~16psi) and everything is ok for the moment.

Those symptoms sound like fuel cut, it happens to me all the time, especially in 6th gear.
Are you sure that's not what it is? Maybe I haven't read this thread thoroughly enough to rule that out, or maybe someone else has already mentioned it.


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## ard978 (May 1, 2006)

haven't fixed it yet. i was out of town the past few days, i'm hoping to get a look at the inside of the forge dv tonight.
as for the fuel cut idea, i haven't looked into that at all. but since this is happening even at lower rpm ranges, is that still a possibility? its also fairly consistent... i'm not sure a fuel cut would be so consistent.
lately i find that if i ease on the gas the problem is nearly 100% repeatable. if i'm a little jerky with the gas when i go to accelerate then the problem is almost non-existent in 4/5/6th gears but in 1st gear is almost unavoidable that i get no boost.
so this makes me think the piston in the forge dv is sticking.... ?
what is the best lubricant to use in this type of application?


_Modified by ard978 at 11:27 AM 1-29-2008_


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## NoRegrets78 (Jul 6, 2006)

Ask forge themselves. I believe it was a mobil 1 grease if memory serves.


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