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whitedog
03-08-2015, 12:17 PM
Car is a 2001 Audi A4 1.8T Quattro Manual transmission AWM engine 124,000 miles.

It throws a CEL occasionally and it has a stored code of 17519/P1111. Car will be running fine, but as soon as I clear this code, the RMPs flare a bit and it runs with a slight miss. After a while, it will smooth out and run fine.

According to RossTech:


17519/P1111 Oxygen sensor control; Bank 1: System too lean

Possible Causes:
1. Mass Air Flow Sensors (G70) faulty
2. Intake Air System faulty/leaking (false Air)
3. Fuel Injector(s) faulty
4. Insufficient Fuel Delivery
5. Exhaust System leaking
6. Faulty O2 Sensor(s)

Possible Solutions:
A. Check Mass Air Flow Sensors (G70)
B. Check Intake Air System for Leaks
C. Check Fuel Injector(s)
D. Check Fuel Delivery Including Pump and Filter
E. Check Exhaust System for Leaks
F. Check O2 Sensor(s) Adaptation Values

I have VCDS so I am looking for a plan to troubleshoot this.

For A, I need to record MAF Spec and Act in a hard pull in third gear to redline, Right?

For B, I saw a post with a dead link to how to make an intake tester. Does anyone have a how to on making that?

For C, I have no idea how to check.

For D, there should be a schrader valve someplace to check pressure, but I don't know where or what numbers I should be getting.

For E, I haven't seen any obvious leaks. They would have to be before the CAT, right?

For F, I don't know where to find the adaption values or what they would mean.

If I knew how to test these things, I could at least get the data and hopefully the smart fellers can help me interpret it.

I tried to set readiness and I don't know what I am doing wrong but a bunch of them would not set readiness. And the ones where I am supposed to hold the brake and the throttle while the computer holds the RPMS at 2200 never did work. It would not hold it at 2200 RPM. Is that because it sees a problem, but just hasn't turned on the CEL yet?

Thanks for any help. She just took the car so I'm not sure when I'll be able to get it back to run any tests.

Wrath And Tears
03-08-2015, 08:06 PM
Most probable cause of this would be an leak in the air system after the MAF, easiest way to diag would be to perform a boost / vacuum leak test. There are several guides on the forum depending what tools you have and what you feel comfortable doing.

Take a look at your fuel trims as they can tell you a lot about what the cause of your lean issue is. These are your "O2S Adaptation Values" and are easiest to check in with a general OBD2 diag tester. I cant remember off the top of my head but if your fuel trims are spiked at 100% then you have a major air leak post MAF, and then theres something about if they look pretty low or normal at idle but then start acting strange when driving its usually a sign the MAF is no good and sending a bad signal to the ecu.

For MAF readings, general rule of thumb is at WOT they should be feeding 80% of your cars horsepower, in.... g/s of air. So 100hp, at WOT the MAF should read ~80g/s of airflow.

If you service your car regularly and have recently done the fuel filter, then your fuel system is more then likely fine.

Exhaust leaks would be from the exhaust mani gasket, turbo gasket, and cat gasket. Most exhaust leaks are hard to see by eye unless they are large and have been going on for awhile (blacked soot marks).

Best way to check for these would be with a type of stethoscope meant for listening to air puffs, or making sure you are able to get full boost with a boost gauge.

Doing the readiness tests are kinda tricky, and cannot be done with any codes stored in the ecu or at least any engine codes. And if a code is pending but not stored it won't trigger a CEL but also wont let you run the tests. It is for this reason I swear it asks you to ensure all codes have been cleared from the vehicle after the proper repairs have been completed and so on.

whitedog
03-09-2015, 05:03 PM
Thanks W&T. I have a partial plan so far.

Figure out how to check for boost leaks (I'll search for that)

WOT run looking for 130-140 G/S on the MAF.

Check into when the fuel filter was changed last.

Look, sniff and feel for exhaust leaks.

That leaves adaption values.

Would I be able to find that on my 2004 A4 1.8T with meaningful results?

RT has a link to two pages about fuel trims and they have it right with my letter F. I think that this means to check there for adaption values.

I was just rereading it and I noticed this:


It is totally normal for both the first and second fields to be something other than zero. In fact, zeros IN BOTH FIELDS indicates that either you just cleared codes (which will reset fuel trim values) or something isn't working properly.

(That is my bold, but their parenthesis.)

Pair this with what happens when it's running fine and I clear the P1111 code. It starts running rough. So that means that the adaptions are set to zero and the ECU has to go back and figure out what it will take to get it to run smoothly again.

So this is the big one to check and I think it should be first. This will tell me what is going on. Maybe there is a post MAF leak, or a bad MAF.

Wrath And Tears
03-09-2015, 07:28 PM
Hey just a quick note, this is the A4B5 thread so A4's from 1995-2001, you have a B6 and even though they are quite similar, there are some differences and you should post to the B6 section of the boards.

You can definitely find the values on your car through the VAG-COM and because you have a newer car there are additional tests you can run. The B6 guys can tell you more. Feel free to copy and paste my response so they can correct any information.

whitedog
03-09-2015, 07:58 PM
My car is the B6, my friends car is the B5. Sorry for the confusion.

Wrath And Tears
03-09-2015, 08:36 PM
Hahaha my bad, got confused and forgot to go reread your post. What I said still stands, you should be able to find the data in VAG-COM, not sure what block it is but RT will say. My favorite way to check for leaks is to use a smoke machine as depending on the type the very gentile pressure created is enough to see boost and vacuum leaks. Too much pressure can often close small holes in vacuum tubes and hide possible vacuum leaks. If you have reset the fuel trims recently driving the car around a bit while you do some of the other tests should be enough to let you see if they are doing anything silly (fuel trims = O2S adaptations, pretty sure you got that but I just want to be clear). I wanna say if they stay in the -10% to 10% range that's perfectly normal.

Edit: http://www.a4mods.com/index.php?page=webcontent/pages/boostleak.html

This guide was brought to my attention by King_Life. Use pressure to find boost leaks and vacuum to find vacuum leaks. I should probably rig this up my self to use.

whitedog
03-10-2015, 04:14 PM
D'oh! I forgot something. When I pulled the O2 sensor out, it was covered in white powder. Does this mean anything?

whitedog
03-16-2015, 07:42 AM
So my MAF readings are fine. I was pulling 148 when going up a hill in second.

Group 32 is at 7.3 in blk 1 and 3.1 in blk 2.

Lambda (I think this was group 2) was bouncing above 10%.

And the white powdery coating on the O2 sensor.

Any clues? Still looking at an air leak between the MAF and the turbo?