P0171 Lean Code Help
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  1. #1
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    P0171 Lean Code Help

    I posted this picture I took yesterday in another post I did about a rattling sound while acccelerating. Could these small holes in the plastic piece be causing the Lean Code? I would think it would be something more. What is this piece called? Air intake? Thanks Joebobphoto.jpg

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  3. #2
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    That can certainly cause a lean code. The ECU is getting more air than expected and this could be the root cause. I think that part is called the snorkel. Good luck!

  4. #3
    Motel Room Moderator VAGguy's Avatar
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    That will cause no lean code at all, actually. That piece is commonly referred to as an air intake snorkel coming from the grill to the opening of the airbox. All pre-MAF. Lean codes are a result of a leak AFTER the MAF sensor. Look around the engine bay for small diameter hoses and check for leaks.

    Update your profile please, or at least give us some vehicle information. Year, engine, trans type. There are three major places to look. Assuming 1.8T. There is an inverted L shaped Home Page > Search > Suction > ES#5939 Breather Hose - 06B133783AT hose leading down the side of the intake manifold to a Home Page > Search > Suction > ES#1884320 Suction Pump - 058133753D Suction jet pump.

    Both the hose and pump are prone to failure. Also a PCV valve that leads from just behind the throttle body to under the intake. Both the L hose and the PCV hose are right next to each other on the intake manifold. Listen for hissing while the engine is running and then clamp one hose shut at a time and see if the sound changes or idle changes.

  5. #4
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    When I had P0171, someone suggested to use a spray water bottle (fine mist) along the vacuum lines and listen to engine idling rpm change. That's how I discovered one of the OEM vacuum tubes cracked at the connector (stress fatigue due to bend). I taped the broken section and the code went away after a while. I then proceeded to replace all 4 hoses with non-OEM ones. It has been 4 years and no P0171 code since.

  6. #5
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    Good advice. I put some duct tape today over those holes on the snorkel and no difference.The car is very sluggish when accelerating sometimes. Noticing bad gas mileage too I believe.

  7. #6
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    Of my four OEM 3.5mm vacuum lines, all but the super-short one to the fuel pressure regulator have failed. I was getting periodic P0171 codes until I replaced the diverter valve and its control hose (the last of the 4 to go). My O2 sensor finally went, as well.

    Now, with a new O2 sensor, new L hose, new F hose (both had holes), diverter valve, and 3.5mm vacuum lines, I occasionally get a P0172 (too rich) code, which I ***think*** (comments invited!) might be caused by a leak somewhere in the boost circuit. I really do need to get a VAG-COM.

  8. #7
    Moderate Moderator Steve in Chicago's Avatar
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    X2 everything VAGguy wrote.

  9. #8
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    I got same code 4 months ago, and was focusing on maf, front O2 sensor and vacuum leak. I replaced o2 sensor and cleaned maf, didn't worked out. But ended up to replace a bad check valve located on the top of air box, no more faulty code.

  10. #9
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    Battling this myself atm: CEL, codes P0303 and P1136 - diagnosis?

    Pls update thread if you find anything. Very annoying, think I might try the spray bottle (instead of building smoke tester)...might just swap out L hose and connected pump for good measure, that seems to be the most common prob outside of vac lines (which appear OK). Check valves all look OK, by which I mean there's no play on either end like previous ones that busted.

  11. #10
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    I just found a leak where a brake booster L hose comes to a T with two other same-material hoses. (The material that these hoses are made of are very odd lol) Until I can get those hoses and the T, I've just put sealant on it which may or may not hold up, but we'll see. It's causing me a bad idle and a P0171 Lean.

    I found it with carb cleaner, water from a spray bottle didn't do anything for me, the motor only bogged down with carb cleaner. But, I heard a very quiet hiss coming from that area, and fiddled around until I felt the leak on that T. Looks like a pain to replace those too.
    Last edited by SleeperWagon; 01-30-2012 at 12:15 PM.

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