# vrT running lean in boost



## schimt (Jan 15, 2007)

i have a 42 c2 tune on my 96' vrT, and i just completed a rebuild of the motor, got her running 3 nights ago and i was running very rich at WOT (less then 10 which is the limit of my wideband), the next day i found a bad boost leak tightened the hose and now it is running very lean, mid 14's at WOT only on 6 psi for now

I obviously stayed out of boost after seeing that
Is there any chance that the ecu is trying to compensate for the rich condition by adapting the fuel map? I tried to reset the ECU by unplugging the battery for a while, the clock reset and stuff, but i dont know if that cleared the fuel trims. The car ran the same after.

i have an inline walbro pump that was used before the rebuild, so i dont think its a fueling issue, especially at only 6psi, also the car idles beautifully and drives great out of boost 

I guess i will bring my work computer home today and start logging things with the vagcom, dont know much about it yet, i know i can find the fuel trims and injector duties somewhere.
Any input is greatly appreciated.


_Modified by schimt at 8:13 AM 11-12-2009_


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## KubotaPowered (Jan 27, 2005)

*FV-QR*

Make sure the walbro is still working, no blown fuses or disconnected wire.


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## schimt (Jan 15, 2007)

*Re: FV-QR (KubotaPowered)*

yea, that thing is so loud! its working for sure. I mean i should be able to run with out it anyways, i only have a 6 lb spring in untill the motor has a decent amount of miles on it. and obviously until i figure out this problem.


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## schimt (Jan 15, 2007)

*Re: FV-QR (schimt)*

i cleared the codes to reset the fuel trims with the vagcom and still no difference.


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## TBT-Syncro (Apr 28, 2001)

*Re: vrT running lean in boost (schimt)*

log your 02 trims at idle. they should be close to 0. if not, then you need to figure out why (maf, o2, tps, cts, etc)


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## turbo toic (Aug 24, 2004)

*Re: FV-QR (KubotaPowered)*

(KubotaPowered) 
Make sure the walbro is still working, no blown fuses or disconnected wire. 



hahaha ....yea def. make sure ur fuse isnt blown lkike mine did


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (TBT-Syncro)*


_Quote, originally posted by *TBT-Syncro* »_log your 02 trims at idle. they should be close to 0. if not, then you need to figure out why (maf, o2, tps, cts, etc)

My wideband reads 14.7 at idle and cruise. And it idles smooth and drives fine out of boost, so i dont think its the MAF. It starts to go rich like low 13's then heads right back up to high 14's and 15's. I get right out of it. I changed the stock fuel pump because it was original and basically the only thing in my fuel system that is no new. But no difference. Im lost


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## marat_g60 (Mar 5, 2003)

*Re: vrT running lean in boost (schimt)*

clogged fuel filter perhaps? Happened to me and ran lean in boost. Do you have a fuel pressure gauge? Also try swapping mafs just to make sure.


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (marat_g60)*


_Quote, originally posted by *marat_g60* »_clogged fuel filter perhaps? Happened to me and ran lean in boost. Do you have a fuel pressure gauge? Also try swapping mafs just to make sure. 

It is a possiblitly but i changed it maybe 3000 miles ago, so i highly doubt it. Yes i have a fuel pressure gauge, but it is not working properly, i have to check the wiring, may be the ground. I am definatly going to try to swap MAF's but i just think that is would idle bad is the MAF was going. Im thinkin the o2 sensor isnt telling the ecu that its running lean, and adjusting the map, but it still should be closer then it is with out adjusting the map.


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## BLSport (Dec 24, 2005)

*Re: vrT running lean in boost (schimt)*


_Quote, originally posted by *schimt* »_Im thinkin the o2 sensor isnt telling the ecu that its running lean, and adjusting the map, but it still should be closer then it is with out adjusting the map. 

C2's software ignores O2 sensor input at WOT, and IIRC even sooner than that on their newer stuff; at load points that would indicate manifold pressure of ~zero or higher (boost).


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (BLSport)*


_Quote, originally posted by *BLSport* »_
C2's software ignores O2 sensor input at WOT, and IIRC even sooner than that on their newer stuff; at load points that would indicate manifold pressure of ~zero or higher (boost).

yea, that makes sense, because a narrowband (the stock o2 sensor) has such a small range that it cant even read how rich it is suppose to be, any ideas on what else it could be?


_Modified by schimt at 1:35 PM 11-17-2009_


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## TBT-Syncro (Apr 28, 2001)

*Re: vrT running lean in boost (schimt)*


_Quote, originally posted by *schimt* »_
My wideband reads 14.7 at idle and cruise. And it idles smooth and drives fine out of boost, so i dont think its the MAF. 

the problem there is that in those situations, the maf could still be giving wrong readings, but the 02 is correcting it. once you're in boost, the 02 is no longer used.
as i stated, log these items, and you'll figure out which is causing the problem.


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (TBT-Syncro)*

yea, the other day i was using the vag com and my car started to die, so i unplugged it right away and not my little brothers laptop wont turn on lol, my laptop has ubuntu and my dad has a mac, i have to find another windows computer or take my work one home. i'll try to switch MAF's with someone and see what happens


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (schimt)*

the new MAF didnt help








I am stumped.
When i had a boost leak and the mbc was turned up to 15 and it was making 8 after the leak, it was running pic rich, now i have it down to 5 psi and the leak is fixed its running lean. Since it was rich at 8 psi, i know the fuel system is plenty healthy, especially for 5 psi. the o2 sensor is out at WOT, i have a new maf, what the f**k else can it be
can the c2 chip go bad?


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## marat_g60 (Mar 5, 2003)

*Re: vrT running lean in boost (schimt)*

do a fuel pressure test and also watch the gauge in boost, it should creep up. Might also try another fpr. There really arnt many parts involved in a fuel system, so you' should be able to solve it quickly


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## pvw4ever (Nov 19, 2001)

*Re: vrT running lean in boost (schimt)*

Having similiar issues








Watching alot of posts on this topic


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## Jefnes3 (Aug 17, 2001)

*Re: vrT running lean in boost (pvw4ever)*

Check fuel delivery....

put pressure gauge on it. 
check pressure under boost.
-Jeffrey Atwood


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## S3.2 (Sep 19, 2009)

*Re: vrT running lean in boost (Jefnes3)*

Is it trying to correct it to 14.7? Are you sure O2 correction stops at WOT? Are you sure it goes to WOT? Even a floor mat under the pedal or a loose Throtle cable can prevent it from going to WOT. Do you see WOT on VAg.com?


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (Jefnes3)*

ok, i'll either get a inline gauge or get my stewart warner one working, it must not be grounded properly or something. I guess i just assumed that since its a new fpr it would be ok, thats a dumb assumption.


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (S3.2)*


_Quote, originally posted by *S3.2* »_Is it trying to correct it to 14.7? Are you sure O2 correction stops at WOT? Are you sure it goes to WOT? Even a floor mat under the pedal or a loose Throtle cable can prevent it from going to WOT. Do you see WOT on VAg.com?

Im not sure, i think when i was logging i never saw it say WOT, i had idle and some type of load, then overrun or something? Its on my brothers laptop, i will have him email it to me when he gets up. I think i also remember only seeing 80 something for throttle position, i dont remember if that was in percent open or degrees.


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## Jefnes3 (Aug 17, 2001)

*Re: vrT running lean in boost (schimt)*

O2 control on/off is LOAD based not WOT only.
just below boost you will see o2 control turn off.
Watch block 001, you see it ~freeze at zero when o2 control is off.
Watch a wideband and you'll see the mix richen as it should for boost.

-Jeff


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (Jefnes3)*


_Quote, originally posted by *Jefnes3* »_O2 control on/off is LOAD based not WOT only.
just below boost you will see o2 control turn off.
Watch block 001, you see it ~freeze at zero when o2 control is off.
Watch a wideband and you'll see the mix richen as it should for boost.

-Jeff

yea thats what i thought, but the problem is i am watching the wideband and it starts to go down to like 13 then straight back up to high 14's and im afraid to stay in it, i always drive out of boost and try it once or twice when i try something new, but no luck, i am going to work on getting the fuel pressure gauge working


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## pvw4ever (Nov 19, 2001)

*Re: vrT running lean in boost (Jefnes3)*

After checking my FPR I found the vacuum line to it was cracked, so far so good. It's richer on high boost and rpm. Some people are running 4.0 bar FPR should I? I have a 3.0 bar now w/ 42# injectors and software.


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (pvw4ever)*

its a brand new vacuum line, i replaced them all because i had a bad vacuum last time around. and yes the c2 software is designed for 3 bar FPR


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (schimt)*

so i got the fuel pressure gauge figured out, had a wire crossed, the fuel pressure is at like 40 at idle with a 18 in of vacuum and just under 45 psi with the vacuum line disconnected. Car runs the same though.
One thing i did notice when checking the vag com was that the throttle position only goes to 73% I was checking it with the car off. I had my buddy do it by hand under the hood incase it was the cable, but the same thing. Could the computer not be switching MAPs because it doesnt think im going to WOT? When driving the "operation mode" goes from idle to part throttle to enrich. not sure if this is right or not.


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## TBT-Syncro (Apr 28, 2001)

*Re: vrT running lean in boost (schimt)*

maybe a bad tps, it should go higher than that. you could take the Tbody off and clean it.


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## KubotaPowered (Jan 27, 2005)

*Re: vrT running lean in boost (schimt)*


_Quote, originally posted by *schimt* »_so i got the fuel pressure gauge figured out, had a wire crossed, the fuel pressure is at like 40 at idle with a 18 in of vacuum and just under 45 psi with the vacuum line disconnected. Car runs the same though.
One thing i did notice when checking the vag com was that the throttle position only goes to 73% I was checking it with the car off. I had my buddy do it by hand under the hood incase it was the cable, but the same thing. Could the computer not be switching MAPs because it doesnt think im going to WOT? When driving the "operation mode" goes from idle to part throttle to enrich. not sure if this is right or not.

Try swapping sensors with someone and see if that helps. Also, if you have the guts to try it, take the cover off the stepper motor on the side of the throttle body and clean the contacts and gears in there. Be careful that you use alcohol to clean the contacts and that you don't remove too much of the grease that coats the gears.


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (KubotaPowered)*

unfortunatly all my buddies have mk4 so no one to swap with. I think they all have 1.8t's too so yea. I may as well pull it apart, whats the worst that could happen? I break it? haha o yea its already broken lol


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## GinsterMan98 (May 19, 2008)

*Re: vrT running lean in boost (schimt)*

My car does not read wot in vag com, it does read 86% partial load though.


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (schimt)*

so i changed the throttle body and there is no change, the vag com reads almost the same thing, 76% throttle when it at full throttle. I didnt take it for a ride yet, but i dont even feel like it. happy thanks giving everyone...


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## drracing07 (Nov 5, 2007)

*Re: vrT running lean in boost (schimt)*

heres something to think about. i have stage 2 42# c2 software in my turbo aba. i had a CEL for some stupid things like engine speed exceeded and multiple cyl misfire cause im dumb and left the vac line off the FPR. anywhoo when i went to clear the dtc's, it wiped all my fuel maps. had to let the car sit and idle for 20 min for it to trim itsself out at idle, it was running about 11 on my wideband. after 10 min it was about to 14. then the more i drive it the more it trims out. now it richens out to about 12.5 or 13 when in boost, i cant remember.


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (drracing07)*

Yea I have like 400 miles on it, plenty of time to adapt the fuel trims, I have cleared it a few times as well to let it readapt after changing things


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (schimt)*

fuel filter didnt help. I am desperate! ideas from anyone please!


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## BLSport (Dec 24, 2005)

*Re: vrT running lean in boost (schimt)*

I see you've checked fuel pressure at idle with/without a vacuum signal, but how about when you're rolling into boost?
I'm curious if it's climbing to match your boost pressure and maintaining; if you're at about 45 PSI without a vacuum signal, it should get up to about 51 PSI at your current boost pressure of 6 PSI.


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (BLSport)*

yea the fuel pressure goes up with boost. The fuel pressure regulator is new too. 
I went to a shop saturday looking for advice, no name haha, and his advice to me was to just turn up the boost all the way, take a couple wide open pulls and see what it does. And that the c2 software i have is designed to run rich only as high boost. What a tard. I really had to bite my lip to not laugh. I know he was just trying to help but i feel bad for anyone who pays him to build a vr


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## steven12345 (Jul 18, 2006)

*Re: vrT running lean in boost (schimt)*

did u check the gauge? just throwing out an idea... maybe something up with the gauge


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (steven12345)*

the wideband gauge? i dont know how to really check it. I was thinking that the rich conidition I had in the begining could have fouled the wideband sensor, but it seems to respond correctly at cruise and idle, unless you guys thing it might be different at higher flows and not read the same...?


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## GinsterMan98 (May 19, 2008)

*Re: vrT running lean in boost (schimt)*

You can't really foul a wide band sensor. It would take a long time of really rich conditions to do that, or a faulty heater element.


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (GinsterMan98)*

yea i figured, just a hope. would make things easy. I am really lost as to what it could be though.


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (schimt)*

so i know its not the right way to fix this issue, but i ordered an adjustable fuel pressure regulator... i feel defeated, hopefully this helps


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## marat_g60 (Mar 5, 2003)

*Re: vrT running lean in boost (schimt)*

make sure there are no leaks between the turbo and maf. Also check all grounds. I had a similar problem before, one of the injector harness was shorting, the compressor housing had rubbed in the main harness and was tripping the ecu out.


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (marat_g60)*

and the car was running lean? if there was a leak between the maf and the compressor i would be running rich in boost because air would be getting out of the system and the computer will mix to much gas. The run perfectly, i drive the car every day, i just stay out of boost.


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## marat_g60 (Mar 5, 2003)

*Re: vrT running lean in boost (schimt)*

Actually in boost it would be sucking air in, if there was a intake leak after the maf then it'd run lean. Worth to check it anyways


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (marat_g60)*

true, duhh, sorry i wasnt thinking, it is still a vacuum before the compressor


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## schimt (Jan 15, 2007)

*Re: vrT running lean in boost (schimt)*

last night i went over it, found one loose hose clamp, so i replaced it, no difference


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## [email protected] (Mar 13, 2008)

I noticed you havnt mentioned anywhere that you have performed a throttle body alignment with vag com. Do this!!! What plugs are you running and at what gap?


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## schimt (Jan 15, 2007)

*Re: ([email protected])*

i have performed TBA's many a times. And if the plugs were not right i believe i would be running rich from a none ignition issue


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## BLSport (Dec 24, 2005)

*Re: (schimt)*


_Quote, originally posted by *schimt* »_And if the plugs were not right i believe i would be running rich from a none ignition issue

There would be unburned fuel present in the exhaust stream as a result of misfire, but there would also be excess oxygen relative to that of normal combustion; this would appear as a "lean" condition to the O2 sensor.


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## schimt (Jan 15, 2007)

*Re: (BLSport)*

sooooo after trying all these different things to find the problem i got an adjustable fuel pressure regulator and turned it up till it ran perfect. and it does, the car feels great, turned the boost up to 10 psi and drove it all night. it's is set just above 4 bar, i dont understand why i have this, because it is the same software and components as the first build and it ran fine with the stock 3 bar fpr, i dont know i am glad it is running good now and i hope this isnt just hiding a bigger problem that is going to bite me in the ass later. anyways if anyone has any comments about how c2 designed for 3 bar and that running it higher is bad news, please let me know and why. Thanks again for everyones help!


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## GinsterMan98 (May 19, 2008)

*Re: (schimt)*

When I put mine together my fuel rail was rusted where the injectors went so I got one of a coil pack obd1 Passat. I was having issues were it was running pig rich. Out of curiosity I looked at it one day and sure enough it was a 4 bar. Took the one out of the original rail at it was a 3 bar. Put it in and it runs perfect with good afr's. It gets lean around 12 psi, but I am still on the 30# tune. 
You also stated that the fpr was new, maybe the o rings didn't seat right? If the inner o ring is leaking it would send some fuel pressure back to the tank through the return line. Also, were is you gauge tapped into the fuel line? How big is the t in the line, because if its too small it could be restricting the flow after the gauge. Last, did you have the gauge and new pressure regulator before this issue or did it develop after? You issue got better due to increasing the fuel pressure by 1 bar, kinda sounds like a restriction in the system and or something screwy with the fpr. Lmk if my ideas sound viable.


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## schimt (Jan 15, 2007)

*Re: (GinsterMan98)*


_Quote, originally posted by *GinsterMan98* »_When I put mine together my fuel rail was rusted where the injectors went so I got one of a coil pack obd1 Passat. I was having issues were it was running pig rich. Out of curiosity I looked at it one day and sure enough it was a 4 bar. Took the one out of the original rail at it was a 3 bar. Put it in and it runs perfect with good afr's. It gets lean around 12 psi, but I am still on the 30# tune. 
You also stated that the fpr was new, maybe the o rings didn't seat right? If the inner o ring is leaking it would send some fuel pressure back to the tank through the return line. Also, were is you gauge tapped into the fuel line? How big is the t in the line, because if its too small it could be restricting the flow after the gauge. Last, did you have the gauge and new pressure regulator before this issue or did it develop after? You issue got better due to increasing the fuel pressure by 1 bar, kinda sounds like a restriction in the system and or something screwy with the fpr. Lmk if my ideas sound viable.

Sup dude,
Well maybe something was wrong with the fpr, but the fuel pressure gauge showed the right pressure and held it, well increased with boost and held it. The tee for the fuel pressure sender is back a ways on the fuel line, kind of under the pcv, i suppose that it could be a restriction but unless the fpr was bad it should still produce the correct psi because the regulator is after the gauge, the pump will have to work a little harder but it should be fine. Also the tee is definatly larger then the hard lines coming from under the car, so i dont think it is too much of a restriction. It is the tee that came with the 42 draft designs kit i bought. 


_Modified by schimt at 7:28 AM 12-8-2009_


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## GinsterMan98 (May 19, 2008)

*Re: (schimt)*

Ok, just thought I would put it out there. The main thing is that you got things rolling in the right direction. http://****************.com/smile/emthup.gif


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## schimt (Jan 15, 2007)

*Re: (GinsterMan98)*

o trust me all comments are appreciated. Yea im glad i can start enjoying her, right as im going to have to put the snow tires on =( at least the boarding season is close


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## maxslug (May 22, 2005)

*FV-QR*

I have nearly the same setup on the same software, but a couple years old. I was having a similar problem lately and ended up doing the same thing -- dropping a 4-bar in and letting it run rich. It works good on smooth dyno pulls, but when trying to feed in part-throttle on the track it's like a bucking bronco. 
Keep us posted if you ever find what's up! I've tried all the same things (MAF, plugs, leaks, coilpack, TPS, etc.etc.etc).
-m


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## schimt (Jan 15, 2007)

*Re: FV-QR (maxslug)*

So I'm down the shore right now in wildwood, a good 2 hour ride and I took the car and my buddy was in his s4. The car run great! Drove most of the way with the boost around 10 psi, stopped to get some gas turned it up to 17ish, holy sh it, feels so right finally, I have no chance against my buddy pulling out of the toll booth awd is nice, I spin the tires through 3rd, but 4th gear pulls from 60 or so, he has no chance







thanks again for everyones help, unfortunatly its raining so the ride home won't be as fun http://****************.com/smile/emthdown.gif


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## GinsterMan98 (May 19, 2008)

*Re: FV-QR (schimt)*

sounds good, glad to hear its working well. http://****************.com/smile/emthup.gif


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## viw28 (Oct 8, 2008)

Bringing this one out of the woodwork lol.... 

Did you ever get to the bottom of what caused this? Did you get it to run properly with a 3 bar fpr? Ever check your mass air flow readings? 

You had exactly the same symptoms as I have been having and I have tried replacing all those components you replaced but to no avail! What I have found is that the volume of air going through the maf isn't high enough but don't know how to cure that :screwy:


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## Boost112 (May 8, 2002)

viw28 said:


> Bringing this one out of the woodwork lol....
> 
> Did you ever get to the bottom of what caused this? Did you get it to run properly with a 3 bar fpr? Ever check your mass air flow readings?
> 
> You had exactly the same symptoms as I have been having and I have tried replacing all those components you replaced but to no avail! What I have found is that the volume of air going through the maf isn't high enough but don't know how to cure that :screwy:


...i am curious as well...


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## masterqaz (Oct 5, 2007)

hmmmmm, i tryed a 4 bar as well as i had gone over all the couplers and just wanted to feel some good old not so lean boost at 13-14. 

It sure does richen up boost but its a band aid fix and causes the car to drive poorly out of boost, i had it in for all of about 10km's. Im curious why it worked well for you and not me(although i understand that its not a proper solution)


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