# 2.7T S4 Running Terribly Lean - Logs & Questions Inside



## 04VDubGLI (May 20, 2005)

I don't actually own the car that is in question, but I ran the logs for a buddy of mine and I don't really know enough about 2.7s to make a good guess as to what the issue is. My first instinct is to say MAF, but I don't know what his MAF readings should be like to even take a stab. He has pretty recently replaced both downpipe 02 sensors. His mods are APR 93oct chip + 710Ns. 
For whatever reason I currently cannot get into my hosting server so I'll just explain what's up and hope someone has some ideas.
His car is a 2000 and it has just over 84k. It's a TIP. 
The issues:
It's correcting 25% fueling in the trims. It's correcting fueling both on the chip and in stock mode. He is getting codes for both 02 sensors reading lean. Way too lean. He isn't reaching requested boost levels - could have something to do with the fact that the car is obviously missing fuel somewhere. He doesn't have a CEL (previous owner bored it out of the cluster) so he never really knows when something is wrong short of it driving differently. His ECU also is supposed to have a 100oct file, but he never knows what mode it is in due to lack of CEL. When it was in "assumed" 93oct mode it was requesting a max of ~18psi and then holding somewhere in the 13psi range IIRC through redline (or as close to it as the TIP would go). His car never saw over like 14.4psi and then tapered to like 11-12psi MAX (tapered immediately before it even reached redline). IIRC the MAF readings were like 130g/s which I thought sounded way low, but again... I don't know anything past 1.8T readings. 

I'll post up the logs later when things are working for me, but that's sort of the gyst.


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## [email protected] (Mar 20, 2004)

*Re: 2.7T S4 Running Terribly Lean - Logs & Questions Inside (04VDubGLI)*

Question: Is this car running GIAC software?


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## 04VDubGLI (May 20, 2005)

*Re: 2.7T S4 Running Terribly Lean - Logs & Questions Inside ([email protected])*


_Quote, originally posted by *[email protected]* »_Question: Is this car running GIAC software?


Nope. Well, supposedly not. It's supposed to be APR. It definitely seems to change w/the stalk, so I think that it's some sort of APR program.


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## 04VDubGLI (May 20, 2005)

Seems as though my buddy was told it could be a leaky injector seal ... Any thoughts from anyone?


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## Eurofvr (Feb 21, 2008)

*Re: (04VDubGLI)*

Hey dude, I think you are trying to buy my tranny on the tex.








So yeah, It could be that the ecu hasn't adapted to the oxygen sensors yet or there is a problem with his fueling system. Hey, he could even have a boost leak. There are many possibilities. I would start by disconnecting the battery for about 10 mins and then reconnect it and do a throttle body alignment. Start the car and let it sit for about 10 mins until the motor settles down to -20hg. If he does'nt have a boost guage just keep the vag hooked up and wait till the idle stops fluctuating. Take her out a see how she goes. GL


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## Landspd (Feb 27, 2008)

Its most likely your mass air flow sensor. Your not supposed to be compensating over 20%, when it does, it is most likely the mass air flow. Especially if you have the bosch mass air flow, I wouldn't doubt it. You may want to do the conversion to the Hitachi mass air flow if your replacing it, hitachis' seldom go bad.


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## Crash6 (Sep 28, 2001)

*Re: (Landspd)*

I have the Hitachi on mine (stock on the 2002).
I have GIAC programming and I sometimes get CEL's for lean conditions.


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## GLS-S4 (Jun 6, 2005)

*Re: 2.7T S4 Running Terribly Lean - Logs & Questions Inside (04VDubGLI)*


_Quote, originally posted by *04VDubGLI* »_IIRC the MAF readings were like 130g/s which I thought sounded way low

Unless heatsoaked, 130g/s is definitely low. A stock 2.7T should be able to hit 170 / 180ish and chipped 230 / 240ish.


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## Crash6 (Sep 28, 2001)

*Re: 2.7T S4 Running Terribly Lean - Logs & Questions Inside ([email protected])*


_Quote, originally posted by *[email protected]* »_Question: Is this car running GIAC software?

Mine is. Lean codes are intermittent, but they keep coming back. If I switch back to stock mode, everything is fine.


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## GLS-S4 (Jun 6, 2005)

*Re: 2.7T S4 Running Terribly Lean - Logs & Questions Inside (Crash6)*


_Quote, originally posted by *Crash6* »_Lean codes are intermittent, but they keep coming back. If I switch back to stock mode, everything is fine.

It suggests something is weak in the fueling that reveals when chipped.
If you haven't already, you could try replacing the fuel filter. I replaced mine as a precaution when going Stage 3- at 50K miles, the filter was original and badly clogged.
I'm running APR with no lean codes in any mode on stock fueling (for now).


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## 04VDubGLI (May 20, 2005)

Problem ended up being an injector seal or two and MAF sensor. Then some other little things showed up... but that was the majority. Just in case someone comes across this later.


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