2005 A8 D3 4.2 (BFM) - Low MPG

[nakata]

Originally Posted by Mechcanico Lee

The vaccum is not as good as it should be Matthew , like i said back there you need to check cam timing first port of call .

If cam timing correct next would be to have a look at variators to see if foot has worn through or fell off .......and the inlet cam timing mark
Cambelt drives exhaust cam ........ exhaust cam drives inlet cam with internal chain .

Cam / crank correlation codes .......... sometimes you get them .....sometimes you dont .....if the cam that is off does not have a cam sensor the ecm does not know that it is out , it can only reference from the cam that does have the sensor ......does inlet and exhuast have cam sensors ?? .

I seen chains stretched to death on vauxhall engines putting cams out loads and still not had cam /crank correlation codes .

In some cases the ecm can only see cams that have gone retared (chain stretch) it can not always see cams that are advanced .....as in someone doing cam timing incorrect whilst doing the cambelt job

From what you write, only show is not familiar with this engine.
And yes is not have 4 cam sensor, only 2.

And no not will give you a fault, but will have rough idle and some time missfire without reason.