2005 A8 D3 4.2 (BFM) - Low MPG

[Mechcanico Lee]

The electric vac pump is there just to assist servo , the engine should still make good vaccum regardless of that , all you are doing with checking manifold vaccum is ruling out any of the places that it can be lost , so gaskets , servo , carbon canister ....any take offs on the manifold , if all take offs are ruled out and vac is still low cam timing is next step

I've heard you can hire the timing kits from somewhere , basic timing needs to be checked first ,.....but in activations can you activate cam timing control advance to watch if it advances and returns to base positions , if inlet cam was stuck advanced it will affect vac .

Also you could drive car on road and watch short term fuel trims and see at what Rpms and load you get the most plus corrections