# Lean Code p171 on 1.8T help!



## Team Audi (Jan 16, 2011)

Hi guys, the car is a 2002 Audi TT Quattro, the code is a P171 (Running too lean -Bank 1).

I have tried diagnosing by checking/replacing the following:

1. o2 Sensors (GOOD)
2. Fuel Filter (REPLACED)
3. Exhaust leak (REPAIRED)
4. MAF Sensor (REPLACED)
5. Fuel Injectors (CLEANED)
6. Vacum Leaks (NONE)

Note: after the car idles for about 1 minute, the RPM's drop slightly too low. When throttle is applied, there is an usual amount of white smoke. I need to get this car to pass emissions ASAP, even a quick fix to get a PASS would be great so i buy myself at least a year to fix the problem, octane booster maybe?....


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## Team Audi (Jan 16, 2011)

I want to also add that ive only owned the car for 1 year and Im not sure of all of its modifications. Here is what I know of:

-2002 1.8T Audi TT Quattro (225hp)
-95K miles, timing belt, water pump, clutch & flywheel, Transmission rebuilt.
- Aftermarket BOV closed system
- 3in" exhaust
- Forge FMIC
- Air Intake (Evolution Motorsports)

This code P171 showed on my car barely a few weeks ago, therefore I believe a part may have failed somewhere and this problem is not due to modifications since these mods have been part of the car for a year or better and have never caused this code in the past...


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## hotgrass (Aug 22, 2008)

check the lines under the intake manifold. when i got that code, the vacuum lines under my intake manifold where all cracked.


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## Team Audi (Jan 16, 2011)

I'll do a double check on them, thanks for your reply Hotgrass


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## lite1979 (Sep 9, 2005)

I've had this code twice. 

The first time, it was a vacuum line that led to my brake booster, but it was on the other side of the engine bay.

The last time, it was a vacuum line that ran under my intake manifold. It was cracked so I cut a short section of it off and put it back on.


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## Doooglasss (Aug 28, 2009)

Team Audi said:


> 6. Vacum Leaks (NONE)


You have a vacuum leak my friend- get searching!


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## Team Audi (Jan 16, 2011)

Awesome info guys, Ive been searching for a leak like crazy :facepalm:

I have an appointment tomorrow with the same auto shop ive already dumped money into but this time theyre not gonna charge me for labor and thats the only reason im giving them another shot.

If they dont find and fix a problem, Im printing out the info u guys have given me and also that reply with the link that Liquid added in and giving it another shot in my own garage, very very helpful thanks again!! :thumbup:

Updates coming soon.....


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## lite1979 (Sep 9, 2005)

Well, in case you get bored, buy some black electric tape. That's how I fixed my first leak (brake booster line near the passenger's side strut tower). The damn plastic piece is ridiculously expensive from the dealership, so I've had it taped off for over a year now with no problems.


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## Team Audi (Jan 16, 2011)

lite1979 said:


> Well, in case you get bored, buy some black electric tape. That's how I fixed my first leak (brake booster line near the passenger's side strut tower). The damn plastic piece is ridiculously expensive from the dealership, so I've had it taped off for over a year now with no problems.


Is this plastic part underneath the top engine cover? I found a plastic piece under there connected to a brake booster metal line... it looks sort of like a disk... mine is getting erroded but no leak on it yet.. btw its an Audi tt 1.8t if this might cover the confusion of where that part is


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## Team Audi (Jan 16, 2011)

UPDATE:

I found a vacuum leak. But I also replaced the bank 1 o2 sensor just in case since the code said P171 lean in bank 1. (The car has 95k miles, its probly considered regular maintenance every 100k). But the cracked line was right behind the intake manifold near the dipstick. Not BELOW the dipstick, but behind the dipstick a little ways up closer to the engine block. There is a short quarter inch black rubber line that had a long slit along the side visible between the gaps in the manifold. I fixed it with some rubber silicone to temporarilly try to solve the problem before I go calling the Audi stealership. In 30 miles my code may or may not return but I will post another update.... I can post some pics if anyone cares to see the location of the leak just ask. Thanks again for everyones help, this is a really good forum! :beer:


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## Team Audi (Jan 16, 2011)

lite1979 said:


> I've had this code twice.
> 
> The first time, it was a vacuum line that led to my brake booster, but it was on the other side of the engine bay.
> 
> The last time, it was a vacuum line that ran under my intake manifold. It was cracked so I cut a short section of it off and put it back on.


This sounds like the same line... Unfortunately my line is too short to cut a section of it and re-connect  so I fixed it with black rubber silicone. Supposedly the stuff is a real good fix on rubber. We'll see if this takes care of the code in a few days...


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## hotgrass (Aug 22, 2008)

hopefully that's it. those rubbers underneath the intake manifold tend to crack due to heat and time.


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## Team Audi (Jan 16, 2011)

hotgrass said:


> hopefully that's it. those rubbers underneath the intake manifold tend to crack due to heat and time.


That appears to be exactly what happened, i did find some hoses with some splits too which was odd


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