P0171; at a loss

[kb03gt]

I can't find a thread I started earlier today so here's a new one.

2004 a4 1.8
130k on body
78k on engine

P0171 bank 1 sensor 1 lean

What I've done to fix this:

SAI removal vac simplification
New fuel pump and filter
New MAF

Known issues with car:
Small exhaust leak on startup.
Probably hurt the engine testing after each repair.

New suspect:
Upstream o2

I don't have vcds yet so I pulled info off a Joe schmo code reader.


https://youtu.be/UJUzZFL4G1g

[Northern_B6]

What I've done to fix this:

SAI removal vac simplification

Did you only remove vac lines associated with the SAI system?
Was there anything else that you removed?

[kb03gt]

I followed the sai removal and Simplification thread on this site. Everything seemed to go well. No change in drivability though.

[mobilesuit818]

sounds like a vacuum leak.

Have you tried the ball vacuum method?

[kb03gt]

That's what I thought at first too. The only 2 lines remaining is the intake to DV and n75 to turbo. The rest is either new or eliminated. Before the removal of the sai I did a leak check myself with no problems found. 2 shops did leak tests with no problems found. In the video it shows the o2 mv and I find that to be off in its response time and readings. Other than that, I'm at a full los .

[Northern_B6]

Sounds like a vacuum leak.

I agree. Inspect whatever vac lines/components that still remain in your engine bay.

Are you auto or 5-speed? If you're an automatic it could be an issue with your brake booster. The lines/check valves/booster pump can leak and cause a P0171, although you would get other brake booster DTC's as well...

Another source of vac leaks can be in your injector O-rings. Easy & cheap DIY.

Instead of looking at the vac line removal thread, have a read here: http://www.audizine.com/forum/showth...-by-a4darkness

This thread should help you identify your vac leak: http://www.audizine.com/forum/showth...e-booster-code

Good luck, I chased a P0171 around for about a month.
Replaced 60% of my vac components and I plan on replacing the rest just to have some peace of mind

[kb03gt]

Thank you for your help. I'm over a month now. 6 speed car. The fact there was no change from before to after. Not using that as an end all be all but I think it's a good idea as to if the problem laid there. I bought a o2 so we will see what that brings. If the injector O rings are faulty wouldn't there be an indication of at minimum a fuel smell?

[Northern_B6]

Your injector seats will look dirty & grimmy. That's a sign that there might be a leak in that area.

[mobilesuit818]

Everyone has a different method for checking for vacuum leaks...
if you have access to a smoke machine, that will be easier.

There is also the the carburetor cleaner method. You pretty much spray a little while your engine is up to temp, but be careful as the fumes are known to ignite if there is a spark anywhere. If the idle goes up, then you found the area where its leaking. I would also do this while moving hoses around with your hand...sometimes a little movement would aggravate the leak some more.

Another thing about that code is that it could also mean your MAF which you said was new.

Lean condition is where you have undocumented air being introduced into the engine...so check your clamps and might try to clean the MAF. Make sure to read how to properly cleaning your MAF with MAF cleaner and a white towel (to see the deposits.)

[kb03gt]

Update: replaced o2. Code for being lean didn't come back after a few hard pulls but I'm still all over the place with boost pressure and detonation. Fml. I'm using the torque pro app and it showed me spiking to 20 psi in first gear. What kind of a/f ratio are we supposed to see at full throttle? I will upload the video of the app and maybe that will she'd some light.

Also: I noticed some oil in the vac lines and tip. Wasn't enough to say omg but was enough to draw attention.

Could the pcv be an issue?
Could the n75 be screwing with me?
Maybe the boost sensor is oil coated?
Ahhhhhh I'm about to sell this and buy a pinto. I love the car though lol.

[kb03gt]

And thank you guys so much. There is a wealth of information on this site. I do have an understanding of how the system operates but this one has me crying in the fetal position.

[kb03gt]

Here's what I pulled.
https://youtu.be/Qp0Aagtvmys

[diagnosticator]

Everyone has a different method for checking for vacuum leaks...
if you have access to a smoke machine, that will be easier.

There is also the the carburetor cleaner method. You pretty much spray a little while your engine is up to temp, but be careful as the fumes are known to ignite if there is a spark anywhere. If the idle goes up, then you found the area where its leaking. I would also do this while moving hoses around with your hand...sometimes a little movement would aggravate the leak some more.

Another thing about that code is that it could also mean your MAF which you said was new.

Lean condition is where you have undocumented air being introduced into the engine...so check your clamps and might try to clean the MAF. Make sure to read how to properly cleaning your MAF with MAF cleaner and a white towel (to see the deposits.)

There is also the propane method, when the propane gets sucked into a vacuum leak, the idle speed will increase. Vacuum leaks represent unmetered air intake.

[EuroxS4]

I use brake clean.But you have to be careful dont want to start a fire.Any chance you have a bad N80 thats not closing??Bad n80 normally will set a incorrect flow fault.But any chances that its hung up?If it stuck it will pickup vapor from the charcoal canister and extra air causing lean code.Any idea on what the fuel trim readings are at vcds mvb 32

[kb03gt]

http://www.audizine.com/forum/showth...simplification

This is now my vac routing. Problem existed before and after this was completed.

- - - Updated - - -

I have also tried propane and carb cleaner. Nothing changed when both were used.