Ok, I’ve got a problem with my 2008 Audi Q7 S-Line 4.2L Tiptronic Quattro. About two months ago I started getting CEL with the following codes:

08585 System too lean at idle, Bank 2 Active/static
08583 System too lean at idle, Bank 1 Active/static

The engine ran fine, however I still had the dealership look at it when the car was there for a safety recall. The came back with a vacuum leak near the back end of the intake manifold somewhere and to further diagnose was going to cost around $2000. I passed on that at the time and about 1 month ago I started to get a loud whining noise from the engine compartment. I was able to track it down to the PCV valve and placed a new one on order to replace myself. About 2 weeks ago, the car suddenly started to idle rough when I pulled up to a stop light and it struggled to continue running. I started heading home and noticed that the engine seemed to run fine at higher RPMs and only struggled to run when at idle. I ran a scanner and received the following codes:

08585 System too lean at idle, Bank 2 Active/static
08583 System too lean at idle, Bank 1 Active/static
08198 Intake Manifold Runner Control Bank 1,Stuck Closed Passive/Sporadic
01287 Idle Control System, RPM Higher than Expected Passive/Sporadic
00768 Random/Multiple Cylinder Misfire Detected Active/static
00775 Cyl 7 Misfire Detected Active/static

I preplaced the PCV valve and went to start the car. For the first 60 seconds the engine ran just fine, then it started to slow down and struggle at idle. I shut it off and rechecked all my connections and everything looked good. I tried to restart and the engine struggled to idle. I decided to go inside and do a little more research at the point. About 2 hours later I tried to restart the engine and once again, it ran perfectly fine for 60 secs then it started to slow down and struggle again. I ran the scanner again and received the following codes:

00768 Random/Multiple Cylinder Misfire Detected Active/static
00775 Cyl 7,Misfire Detected Active/static

On a hunch, I tried letting the car set for a couple of hours and then restarting and once again it ran fine for 60 seconds (idled at 1200 rpm) and then struggled (rpm drops to 600-800) with the same fault codes. I would then immediately restart the engine and it would immediately struggle to idle. I have to use the accelerator to keep the engine running and it seems to smooth out around 1200-1400 rpm, however the CEL will flash. I repeated this same test 3 mores times and had the exact same result with the engine running fine for 60 seconds after having been shutoff for 2 hours.

I have spent days researching the various reason for misfires and I and the best reasons I can come up with at the moment for this problem is that there is either still a vacuum leak somewhere I have not found yet or possibly there is a problem with the battery(although this one seems like a stretch to me). I have also tried swapping the coil packs around with no change.
I’m suspecting a vacuum leak since the 2 hour time would between starts allows the pressure in the engine to return to normal vs the immediate restarts in which the pressures inside the engine would be closer to the running pressures.
Any help here would be greatly appreciated as this is the car my wife uses to get to and from work and we really can’t afford a massive repair bill right now.

Thanks

 

UPDATE: Problem found. The cam plug missing on the backside of the engine that prevented the crankcase from building up any pressure. Once it was replaced, the engine runs perfect again.

 

 

Sorry, I ended up having to take it into my repair shop locally. They were the ones that found the plug was missing and replaced it for me. The cost for the part was around 5 dollars and its located on the backside of the engine. I suspect that the dealership may have loosened my up because I did have the car in with them for the fuel system recall and that work would have been in the exact same area as the plug.