Audi 4.0 Rich condition / stalling at idle

Bill Owner/Technician Jackson, Michigan Posted   Latest  
Question
Driveability
2013 Audi A8 Quattro L 4.0L (CEUA) 8-spd (0BK)—WAUR2AFD2DN004929
P0175 - System Too Rich Bank 2
P0172 - System Too Rich Bank 1
P0300 - Random/Multiple Cylinder Misfire Detected

Vehicle struggles to idle and stalls, after it stalls necessary to hold down gas pedal while cranking to start. sometimes smokes from tailpipe when restarting... low and high side fuel pressure matches specified vs actual. After shutting off engine fuel pressure values do increase with heat soak - so I don't currently suspect a leaking injector. ECT value normal at 80c. Fuel correction is very rich both bank 1 and 2. (-19% -16%) i reset the engine controller and restarted both banks -25% within 1 minute. Looking for diagnostic advise

0
Bruce Manager
Lansdale, Pennsylvania
Bruce Default
 

You are using VCDS - did you email our team? Support@…​.​com with an AutoScan and point them to this thread.. Or, post in our forum where not only our techs but others around the world are willing to assist. I'm not a tech so I would not want to try to give you guidance. I have a 2010 Tiguan with the 2.0L 4 that is behaving similarly. We were thinking ECT, IAT or possibly a…

+2 Default Ð Bounty Awarded
Voit Owner/Technician
Freeport, Maine
Voit Default
 

It is most likely the turbo(s)... It does not make sense that it would be rich but this is what happens. The sensors thinks it's under load and add fuel. The turbos each feed cylinders on both banks so even one bad turbo can affect both banks. Look in to the intake of each turbo with a boroscope while running and you will likely see one turning slower if at all. You can also look for damaged…

+4 Default Ð Bounty Awarded
Samuel Technician
Somers Point, New Jersey
Samuel Default
   

So Voit, does this mean that at all times, no matter what, when the engine runs, idles or is WOT that the impellers will move because of the exhaust that flows by design....is there any condition that the manufacturer would intentionally stop the flow and propellers for possibly a federal emissions reason???

0 Default Ð Bounty Awarded
Voit Owner/Technician
Freeport, Maine
Voit Default
 

Yes, the turbos are constantly spinning whenever the engine is running. The MAP sensor interprets the pressure. When these turbos fail it seems that the DME thinks that there is load on the engine and adds fuel (significantly) even at idle. To your question about the turbos stopping spinning for some reason is not possible. The pressure (or vacuum) could only be vented to the atmosphere.

+1 Default Ð Bounty Awarded
Samuel Technician
Somers Point, New Jersey
Samuel Default
 

Thank you for the answer!!!!

0 Default Ð Bounty Awarded
Jay Diagnostician
Norcross, Georgia
Jay Default
   

Does your fuel trim stay rich even if you step pedal to Wot? or does it start to lean out? Because if it’s affecting both banks mass airflow sensor Is shared.

0 Default Ð Bounty Awarded
Caleb Technician
Mishawaka, Indiana
Caleb Default
 

I am by no means a VAG tech, but I'll share some thoughts. So I know hot soak KOEO the rail pressure is rising. I have however seen high pressure pumps still leak fuel in to the crankcase when they are running. Since you have an idle problem also I would be capping off the CCV system and checking the trims again. After verifying that's okay check for overfilled engine oil, stuck open purge…

+3 Default Ð Bounty Awarded
Bob Owner/Technician
East Longmeadow, Massachusetts
Bob Default
 

Bill, Have you monitored fuel trims under load and high rpm as well as idle? It would be helpful to know if the issue is at idle only or at other speeds and loads too. That would give some direction. Also, I hate to be nit picky but I think it's important to get the terminology right to keep the discussion on track. You said the fuel correction was very "rich" at -19%-16% A negative fuel…

-2 Default Ð Bounty Awarded
Bill Owner/Technician
Jackson, Michigan
Bill Default
 

Bob, Perhaps you have gotten to hot at work today.... A rich condition creates a negative fuel trim as the ECU is subtracting / removing fuel... -25% indicates a rich condition is present A lean condition creates a positive fuel trim as more fuel is added... +25% indicates a lean condition is present. Bob I am sure we both understand how fuel trim works! Let's please stick to the problem at…

+1 Default Ð Bounty Awarded
Mark Owner/Technician
Chesterton, Indiana
Mark Default
 

Bill, have you checked and are positive there is no fuel mixed with the engine oil?

0 Default Ð Bounty Awarded
Bob Owner/Technician
East Longmeadow, Massachusetts
Bob Default
 

"A rich condition creates a negative fuel trim as the ECU is subtracting / removing fuel... -25% indicates a rich condition is present" I agree with that statement completely except to say that the TRIM is LEAN. A RICH trim would be +25. "Bob I am sure we both understand how fuel trim works! Let's please stick to the problem at hand and not act like we are on that other site...." I know, it's…

0 Default Ð Bounty Awarded
Bryant Technician
Salt Lake City, Utah
Bryant Default
 

your comment is incorrect.... of "negative" readings on fuel trims is inaccurate... negative readings mean that the computer is seeing "too much" fuel by the O2 sensors; thus the computer is "taking away" or going negative on fuel trims trying to compensate back to a acceptable value ideally 0%

0 Default Ð Bounty Awarded
Bill Owner/Technician
Jackson, Michigan
Bill Update
 

I used a borescope to view the turbo impellers while having another tech hold RPM at about 1000. Noted left side was not spinning at all. Removed the intake pipes from both turbos and found Both left and right turbos failed with excessive looseness on impellers. If you zoom in on the pics you can see markings on the impellers and bore showing contact. They have 1/4" to 1/2" of movement!

+2 Update Ð Bounty Awarded
James Owner/Technician
Pike, Pennsylvania
James Default
 

I'll be very interested to hear the result of this repair if you get the go ahead to replace the turbos because I just had a similar issue with a Audi A5 that is due to come in next week for diagnostics and I never considered the turbo as a possible issue.

0 Default Ð Bounty Awarded
Stuart Owner/Technician
Prestonpans, United Kingdom
Stuart Default
 

Good shout, that’s a case where we have all Learned something new.

0 Default Ð Bounty Awarded
Bill Owner/Technician
Jackson, Michigan
Bill Default
 

Follow up --- Vehicle was repaired with 2 new turbo's- no further issues with driveability were present... Found the driver's side turbo had broken off the turbine wheel it was completely disconnected from the compressor wheel... Check out the pics

+3 Default Ð Bounty Awarded