Code P0171, bad MAF or vac leak?

[turbo_bootin]

Hi all. I'm new to Audis and I just got a 2001 A4 1.8TQM. I love it, it's a great car but it has a check engine light on. I went to Autozone and scanned it and got the following code:

Code P0171: System Too Lean (Bank 1)

I looked that up on here and vortex and it led me to believe it was the MAF. I tried cleaning the MAF with isopropyl alcohol. However, this only made the car idle funny (RPMs bouncing around between 750 and 250. It even conked out once.)

So I went back to Autozone and bought some MAF cleaner and tried that. Now it's running a little bit better, it no longer jumps at idle (It still drops low when I start it though.). When I was taking out the MAF to clean it, I noticed what looked to be a leak in something (check valve? Is that what it is?) Could that be the source of my code and idling problems?




Thanks.

[Poopie]

Yes get a new check valve

[slingshot]

There's your leak right there.

[turbo_bootin]

Alright, thanks. But why would it start idling funny after I cleaned the MAF?

[slingshot]

Alright, thanks. But why would it start idling funny after I cleaned the MAF?

It should have been idling somewhat funny to begin with since you have at least one vacuum leak. But you may have damaged the MAF or got some dirt or something in the connector.
Also possible you aggravated your one or multiple vacuum leak(s) when you were in there poking around.

Go through the engine bay and check all the vacuum lines. It's easy since there are only 55,000 of them on this engine. Inspect all those little check valves and doohickies and make sure you've taken care of every little hose and connection that might be leaking air. Then re-check the MAF and connetors. Alcohol is generally pretty safe, but you have to be careful how you apply it. MAF's are very sensitive. Double check the clamp on the hose attached to the MAF as well. Could be something silly like that.
Also, I'm not familiar with the MAF on this car, but in many cases the actual MAF sensor is tucked up into the tube, and the part you can see is actually the intake air temp sensor or something similar.

[biketsai]

I hate the P0171!!!!

[McGovs2.7TB5]

OK, so this code comes and goes on my '01, CEL will be on for a couple days then off for 5 then back again. Most of the time when its on I'm in limp mode. My gauge doesnt show any abnormal vac pressure amounts so I'm leaning towards the MAF. Has cleaner ever really fixed the problem or is it a stop gap to buying a new one? Thanks

[Seerlah]

It is always worth a try to use CRC MAF cleaner before purchasing a new MAF. Figure $5 (MAF cleaner) vs. $125 (New MAF). Never hurts to try first. And yes, CRC MAf cleaner has fixed a MAF in many instances. That is the case when the MAF is not faulty, but simply dirty (which can lead to it being faulty). And you won't know, unless you try and clean it first.

[biketsai]

OK, so this code comes and goes on my '01, CEL will be on for a couple days then off for 5 then back again. Most of the time when its on I'm in limp mode. My gauge doesnt show any abnormal vac pressure amounts so I'm leaning towards the MAF. Has cleaner ever really fixed the problem or is it a stop gap to buying a new one? Thanks

Def the MAF. I used to have that issue, replaced it and I was completely fine. You can try the cleaner, but if your sensor is just bad, then it may not work out.

[audijet]

I have the 2004 Audi 1.8T.

Check engine light is on. I have my car diagonesed at Autozone, code P0171 & P0507 were read. See the picture, is that the problem that caused check engine light?



This is what I am planning to do. I will go to the dealership and get the part, then drive up to a mechanic shop and ask them to change it for me, or any forum members can provide some good tips to change the part.

Just wonder is the car still safe to drive in the next couple days until I have time to bring the car to the shop.

How much is it costs to fix the problem in dealership? Thanks.

[dcampana]

^^ dude, just buy the check valves and then go buy some new hose clams. take old one off and out new one in (just put it on the right direction.... dont pay someone for something this easy... save your cash for real problems:):) if you can turn a screwdriver, you can handle this!!! there are better things to buy than labor.

[audijet]

Is this the one I need to buy.

http://www.ecstuning.com/Audi-TT_MKI.../valve/ES3022/

[spider]

is there a way to check if the maf sensor is bad and needs to be replaced?

[rmamiye]

can the in-line check valve really cause so many problems? burning rich, heavy idling, loss of power among other symptoms...

[RockyMountainB5]

Is this the one I need to buy.

http://www.ecstuning.com/Audi-TT_MKI.../valve/ES3022/

Not unless you want to pay $30 for that stupid little valve.
heres the one you need: $10....
http://www.ecstuning.com/Audi-TT_MKI...alve/ES259630/

or, you can just purchase a generic one from Napa, Autozone, etc - its just a diaphragm valve that prevents gasses from going in a certain direction. So, any check valve will work - one that can handle up to -25 in/HG vacuum, and up to +25 PSI boost.

[rmamiye]

i just replaced the inline valve check that was corroding. after driving a few minutes on the new one i notice tthat im still burning rich as well as my turbocharger is glowing red.
any ideas as to why this may be?