If you remove the oil filler cap whilst the engine is running and the variation in engine speed / rough running improves significantly then it is likely it could be the PCV valve for sure +++

Thanks Architex,
I’m still trying to sort out my misfire issue and +25 fuel trim on bank-4 so looking out for anything abnormal.
I’m prepared to replace Lambda sensor and clean injectors but i understand the inlet manifold flaps can break off and cause the mixture to be off...

I’m taking it all apart again on Monday but VCDS activating the intake manifold test first and will inspect with a camera. Otherwise I’ll continue on to remove and service injectors and replace Lambda S1 Bank-4 while i’m At it. Fingers crossed...

Thanks again...

Update

Ok so all apart again.
Completed intake manifold activation test with VCDS and flaps look perfect.

I have removed the injectors sending to service and test. I had one stuck injector and after waiting on the eBay sourced, FSI removal/installation kit - injector was removed fine.

Research on eBay I found: Injectortune in Wiltshire, can do these injectors so fingers crossed all returned by next week. The challenge now is replacement seal/fitting kits. So far China has these with 2-week lead time. Waiting on Audi to quote...

I’ll update as this develops (this is taking rather long)

Cheers

James at injectortune runs a D2 S8. Or at least did in the past. He did 10 injectors on mine. All good...

The sage continues lean codes and V10 rough idle
 

Hi all, so now all injectors serviced by Injectortune, and refitted with new installation kits, new Lambda sensors bank 2 and bank 4, new Oil separator fitted, and still having this intermittent rough idle. After spirited driving the CEL is on again with the following codes by VCDS:
Bank 1. System too lean at idle. P2187 - 004
Mixture regulation Bank 3 range 1. P1081 - 004 - lean limit exceeded - MIL on.
Mixture regulation Bank 4, range 1. P1085 - 004 - lean limit exceeded.

Looking at the above can anyone suggest additional checks... it looks to be a vacuum leak... possibly?

I can not remove the oil filler cap with the engine idling due to tremendous vacuum - is this normal? On other web threads this points at a faulty oil separator - please let me know what is normal.


I’m at my wits end on this car - so much work and No cigar...

Thanks guys,

From memory the oil seperator / pcv valve isn't hugely expensive on the D2 so perhaps its an idea to change it and see if it resolves things and gets you back to smooth running

Thanks Architex,

I have ordered a new breatherAGAIN but the more costly one. The £38 one was only recently fitted and must be a dud.....

I’ll report again on progress.

Cheers,

Hi, today a fitted another new PCV oil separator and also vacuum tested the fuel tank breather solenoid valve N80 (tested ok). Started the engine and I am now able to remove the oil filler cap with engine idling (well I couldn’t before). So it just goes to prove that cheaper parts on EBay £32 compared to the better £80 Bosch part makes one hell of a difference in quality and function.

Next step - check VCDS for Lean operation after completing my recovery from retinal detachment surgery, hopefully early next week.

Fingers crossed,
Thanks again folks!

+++

Update, well a few hundred miles later and all is well with the car. Idling smoothly, starting and running very well and no engine fault codes - great.

Thanks for all your comments and support��

It’s been a costly and time consuming project to get this car up to the level it’s at. Thinking on a new project now so may consider selling the S8 next.

Cheers