P1136 & P1138 Issues
 

I have the following codes on my car and the check engine light is on,

17544 - Fuel Trim: Bank 1 (Add): System too Lean
P1136 - 001 - Upper Limit Exceeded - MIL ON
17546 - Fuel Trim: Bank 2 (Add): System too Lean
P1138 - 001 - Upper Limit Exceeded - MIL ON

I guess one starts with checking the vacuum lines first, or should I check other things first?

I was inspecting the vacuum lines at the rear of the car and there is one component "vacuum diaphragm?" which I noticed was taking in air at the top where there is a small gap is this normal? see attached pic of the part.

Attachment 10640

Anyone have a schematic of the vacuum lines as the Bentley Manual seems disjointed.

I also noticed that the vacuum pods "links" plastic were broken. I popped them of and put on the aluminium ones from www.GruvenParts.com. But the car started to blow white smoke from the exhaust, not sure if all this is related.

(A8L 2004 BFM engine)

That is your PCV valve (crankcase vent). It should not be sucking in air from outside...that could be introducing unmetered air (major vacuum leak...ruptured valve?) into the intake, which would cause a lean fuel-mixture condition.

The links on the front of the intake manifold control your intake changeover...different lengths of intake tubes for different rpm ranges, to keep torque curve up through the range. Should not effect color of exhaust smoke. This system is working properly if both vacuum pods connected to those links are full (blown up) when engine is off....and both fully evacuated (sucked in fully) as soon as the engine is started and idling. If they are NOT doing this see this procedure: http://forums.audiworld.com/showthre...2801728&page=3

BUT, that procedure has nothing to do with lean burning condition.
You need to check out the PCV valve (your photo)...as I stated, should NOT be sucking air on top of the valve...likely your "lean" problem.

Old thread, but I have the same codes P1136 and P1138. I'm wondering if it's the MAF or O2 sensors. I have 135k miles on my car.

Does anyone know the specs to test the MAF with a multi meter?

I have the same lean codes. both banks. checked vacuum lines, cleaned the MAF sensor, no codes for oxygen sensors so I doubt it's that. Also no code for MAF sensor. Just lean bank 1 and lean bank 2. I also have an issue with blue smoke from the exhaust, but only after it sits at idle for 15 or 20 minutes and then sits over night it will smoke at start up. If I drive normally, it never smokes at start up, so I don't think it valve seals. I will check the PCV valve. That sounds like a common link. How do I check this PCV valve ?

I changed the PCV valve and that fixed everything. You will notice it sucking in air. Its the one in an earlier picture.

GREASE - Thanks for coming back to confirm, my PCV valve has that open space like yours. They could all be like that but maybe the internals failed causing the leak/codes.

I found one for $84.00 on RockAuto.com , I might just get it as my car has 135k miles.
More Information for STANDARD MOTOR PRODUCTS V465

PCV Valve
 

I assume there's no fix other than replacement ?
I will dig into it and post the results. could take some time as I have a lot going on personally.
thank you so very much for the point in the right direction !
there doesn't seem to be a ton of know how on these cars and engines on these forums. Seems most like the smaller cars, and that's what they know.
please keep posting your experiences. I will too.

I ordered the PCV Valve from RockAuto and I'm going to put it in this week, I will report back to see if it removes those two codes.

I also need to fix my driver's side flex pipe exhaust leak. I don't think that is causing the two codes because I would probably only get one bank reporting lean not both.

The PCV valve is not fixable, you will notice it sucking in air at the top of the valve center, pretty load hissing coming from the top of it. Feel air going in through the center?

Installed new PCV valve but the light came back. I'm going to check the MAF measuring blocks as well as fix the exhaust leak. I'm not getting any strange O2 codes so it's probably not them. I'll look around, but I don't think I have any vacuum leaks

I have changed both,

PCV at 109485K 7/17/2011


MAF Check Engine on 121608K
1/6/2013 17536 - Fuel Trim; Bank 1 (Mult)
P1128 - 001 - System too Lean - Intermittent - MIL ON
17538 - Fuel Trim; Bank 2 (Mult)
P1130 - 001 - System too Lean - Intermittent - MIL ON
Readiness: 0000 0000

Cleaned MAF and cleared the codes worked for a while but ended up changing it 300 miles later

Thank you, so it really seems like the MAF could be the culprit. I have 135k miles on the car too so it could be the original MAF.

GREASE - So did replacing the MAF clear both codes?

*UPDATE*
Unplugged MAF with the car off, then turned the car on and it idled exactly the same. Sounds like it could be the MAF now, the car "should" have run crappy with it unplugged.

Yes changing the MAF worked for me.

my PCV is fine. I can find no vacuum leak there. no sucking sound.
I've cleaned my MAF sensor twice now with CRC MAF sensor cleaner. lean codes came back after a short while.
How'd the new MAF sensor do you ?

The new MAF didn't get rid of the codes, they came back :( I have a pretty bad exhaust leak from the flex pipe so that will be my next thing

Sounds like you are both hitting a road block. Perhaps one of the Audi Techs on the site can help.

P1573 - Left Engine Mount Solenoid Valve (N144): Open Circuit
P1575 - Right Eng. Mount Solenoid Valve Short to B+
P1874 - Valve for Torque Support Mount: Short to Plus

I also get the above codes along with the lean codes below... The lean codes are the ones that trip the check engine light.

P1136 - Fuel Trim: Bank 1 (Add): System too Lean
P1138 - Fuel Trim: Bank 2 (Add): System too Lean

Grease - I've tried. No answer so I assume they don't know. I think they are more familiar with the smaller cars. Was really hoping the MAF was it. I've also replaced the fuel pressure regulator with no improvement.

these are just the engine mount dampening solenoids mine are both out too, they are supposed to smooth the vibration of engine to the body. At $400 plus a unit I didn't bother to change them.

P1573 - Left Engine Mount Solenoid Valve (N144): Open Circuit
P1575 - Right Eng. Mount Solenoid Valve Short to B+
P1874 - Valve for Torque Support Mount: Short to Plus

Ok yep I remember reading that these are common to fail and they won't hinder the car very much.

These lean codes are tough, I have a pretty significant flex pipe leak so that could be it but on Josh's car it doesn't seem like he has any glaring issues that could be the culprit

160,000 miles on it. maybe injectors. I'll fart around with my VCDS and see if I can view the oxysensor codes. maybe they are just old and going out of spec. I'd like to try an adjustable fuel pressure regulator and bigger injectors. anyone know of a kit ?

Yea I was thinking of playing with the fuel to see if the filter/pump/injectors were causing the code. I know a vacuum leak or O2 sensors are more likely than a fuel issue. Not sure of any fuel kits, these cars really don't have a mod market. I have to buy the Vag Com and check the specs of everything.

Finally got my Hex + Can + USB Vag Cable and did a few 2nd gear logs. Let me know what you think of the logs. I'm guessing the peak MAF reading should only be at 6500 as that is where the car makes the peak HP of 330? I know Ross-Tech says that your MAF reading during a pull should be .80 * HP. So I should see 265 g/s.

From Ross-Tech Wiki:
Fuel Trim Info - Ross-Tech Wiki

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. If values get too far away from zero, it will cause a DTC (fault code) and can set off the MIL (commonly referred to as the Check Engine Light, or CEL). Specifications for normal operation are usually somewhere near +/- 10%.

In general, an out-of-spec value in the first field (Additive) indicates a vacuum leak since it is mostly present at idle, when vacuum is highest. An out-of-spec value in the second field (Multiplicative) indicates a fault at higher RPM, and may point to a faulty MAF.


Also, I have a brand new MAF and this is my MAF READING @ IDLE: ~2.72 g/s

It looks like the (Partial) throttle trims are the ones tripping the CEL light as they are more than 10% as shown below:

BLOCK 032:
Adaptation (idle) B1S1: 6.2%
Adaptation (Partial)B1S1: 12.5%
Adaptation (idle) B2S1: 6.0%
Adaptation (Partial) B2S1: 11.7%

ENGINE LOAD %- Is this supposed to be 100% at WOT? As you see mine is in the 80's. Not sure why because it sees Full Throttle and Throttle Valve Angle = 100.

Press the + magnifying glass on the bottom right to zoom in, you will need to press it twice.

2004A8L_LOG2_zps2c911358.jpg Photo by Rn3040 | Photobucket

2004A8L_LOG1_zps1b4d9915.jpg Photo by Rn3040 | Photobucket

Also noticed that I have a readiness issue w/ Catalytic Converter(s) Failed or Incomplete. The car was warmed up when I saw this and the cat temps were ~580+ degrees.

https://i7.photobucket.com/albums/y2...pse5c87e28.jpg

*UPDATE*
I noticed my gas cap has ZERO sound of pressure release when I open it. Any ideas if there could be an air leak in the EVAP system or somewhere causing the lean codes?

Hi,

Here is what I found :

photo 3 is a pic from google - it seams like the same engine (I am not 100% sure)
photos 1&2 - my engine. The red circled thing has a cap (removed in the photos)

I find interesting that on my engine there was a cap on this thing "opening" but on the other engine (pic 1) there is a tube leading somewhere...

I when to the dealer they said - "it is normal - the cap is suppose to be there, no tube in our database"

Some thoughts ?

Pretty sure my car has a hose on that nipple, so yours was capped off? I'm not sure what, but the previous owner might have bypassed something by capping it.

Do you still have the lean codes?

Yes, I do!

Have gone to the dealer... they said it is supposed to be capped.
I also have found it on ETKA -it really is supposed to be capped.


But i still get the fault codes

If you have a Vag Com, check block 001 and 031 at idle when you first start up. For some reason my car goes lean at idle until the temp is 33-55 degrees. Or at the point the RPMs drop from the cold start. Looks like this is causing the codes.

IACV?
Do our cars have an Idle Air Control Valve? I'm wondering what else besides that OR the O2 sensors are bad and putting out mixed signals until they heat up.

You can see this here in my log, I put some yellow lines where the Air Fuel is normal. I also noticed that when it's lean, the actual fuel corrections are at ZERO. The car isn't lean when the fuel starts correcting.

https://docs.google.com/spreadsheet/...EE&usp=sharing

NEW O2 Sensors
NEW Intake Manifold Gaskets
NEW Injector O-Rings

I installed the above items but I still have the fuel corrections at idle on a cold start. The fuel corrections go from 10-12% down to 0 or negative once the car reaches 60-90 degrees. You can see the change start happening in my log file around ROW 545.

Any ideas on what could be causing the addition of 10-12% fuel only at idle until the car warms up? The car is also very lean on a cold start sometimes, Block 031 shows Lambda at ~1.3-1.4 during the high idle cold start, then it settles down to 1.0 when the RPMS drop. I have no secondary air injection codes but I think it's broken, I can't hear or feel it working, not sure if that could be causing this.

LOG FILE
https://docs.google.com/spreadsheet/...mc&usp=sharing

MAF UNPLUGGED RESULTS
The MAF that was currently in this car was from my 2006 A8L that had no issues. Also note, the car ran exactly the same with the MAF unplugged because when I plugged it back in, the RPM and engine sounded the same.

***Air Fuel Lambda was on the rich side then the O2's corrected up to NEGATIVE 25%
***BLOCK 107 PASSED! Any ideas on what is causing this behavior?

https://i7.photobucket.com/albums/y2...pse99cf462.png

https://i7.photobucket.com/albums/y2...ps9fd94e63.png

https://i7.photobucket.com/albums/y2...psbd9ff751.png

*FIXED*
Used smoke machine at my local mechanic shop, big leak on the valve cover gasket. The stupid thing about this is that I actually did the valve cover gasket when I bought the car so when I re-installed the gasket I must've 'creased' part of the gasket so it didn't seal. Lesson is ALWAYS look at the simple stuff first and if you 'touched' anything on the car.

no way !!

do you mean intake or valve cover gasket ? how does a valve cover gasket cause this ?

congratulations !

Thank you! Yes it was VALVE COVER GASKET so that would basically be an internal air leak on the engine.

!!****FIXED****!!
Mine turned out to be the MAF sensor. It finally gave out. Replaced it with an OEM Bosch unit for $150. Not a cough since. No MIL/CEL. Happy Day ! It must have been gradually fading, as I didn't notice the performance dropping but it definitely was. Power is back with a vengence ! Also noticed the MAF sensor and Fuel Pressure Regulator are different part #s from the A8 same year. Didn't replace the pressure regulator, but I might just as a maintenance item.