Lean Codes

A6 All/ S6 All
#1

While taking a few hundred mile drive about a week ago I had the following codes pop-up and illuminate the MIL

P0174 - Powertrain - System too Lean (Bank 2)
P1075 - Powertrain - O2 sensor too lean (Bank 3)
P1077 - Powertrain - O2 sensor too lean (Bank 4)

I could not detect any drive-ability issues and the car revs just fine. I cleared the codes and they were gone for about 2 days of light driving but have now come back.

I noticed another thread with the same O2 codes but also a Fuel Pressure code which seemed to indicate the HPFP, however that issue also caused a failure to rev properly which my car is not having.

I believe these codes are all pointing to the driver side bank of cylinders. I plan to check for any split hoses or air leaks tomorrow but I just changed the air filters about 2k miles ago and both sides looked really good. Could this also be a failing HPFP? I do have a full VAG-COM cable so I can take logs but I’m not sure what I should check.

Any help would be appreciated, thank you!

#2

Forgot to mention this is a 2007 S6

#3

So I cleaned the MAF sensors a few days ago, checked around again but didn’t see anything. The codes came back in about a day so I pulled the full codes from VAG-COM and it is showing lean conditions only at idle.

http://audirevolution.net/addons/albums/images/496512590.jpg

http://audirevolution.net/addons/albums/images/589611561.jpg

I’ve also noticed that when driving in stop and go situations, in heavy traffic for example, the car is very jerky on/off the throttle.

Hopefully somebody has some insight!

Thank you

#4

When was the car last carbon cleaned?

#5

I cleaned it about 1k miles ago, I do it every 12k.

Just realized I posted the same picture twice in my last post. Here is the correct image of the readout for the second ECU:

http://audirevolution.net/addons/albums/images/159926991.jpg

#6

Codes like that signal a vac leak of some kind. As you mentioned check all hoses connections and re tq the bolts to the intake manifold both the upper air intake and lower portion that connects to the cylinder heads.

#7

I checked all the air hoses I could see again and they all seem fine. The torque on the manifold and upper manifold thing were good, however it looks like there is a bolt missing at the back of the upper manifold piece
http://audirevolution.net/addons/albums/images/591602562.jpg

Not sure if that would cause this, but does any know if this is a missing bolt? And if so, does anyone know the size?

#8

If that bolt goes to the intake Y section that the throttle bodys connect to you are probably going to really want to replace that bolt. If not I don’t remember it being an issue. I’m trying to remember what it goes to but if not the Y I think its a mounting hole.