Quote:
Originally Posted by Mechcanico Lee
The electric vac pump is there just to assist servo , the engine should still make good vaccum regardless of that...
|
Mechanico Lee, you are a saint for your thorough, scientific method of tackling this problem (should say these problems). Is there an auxiliary vacuum pump on the petrol engines? Should I disconnect it while checking manifold vacuum?
Quote:
Originally Posted by MatthewH
...Will also check fuel pressure while driving to hopefully rule the fuel pumps out.
If none of these ideas give me any clues then it may be time to take it to a specialist for diagnostics.
Thanks.
|
Seems Lee is a better "specialist" than you'll find locally.
Can you see function of fuel pumps 1 & 2 on VCDS? I cannot believe considering the thousands of sensors Audi uses on this engine that there's not a fuel pressure sensor or two on this "BFM"!
I am having the same problem with my new 2004 A8L. Thrilled to have found this thread since it's so methodical and complete. Thanks, guys.
BTW, I'm lucky enough to have two '04 A8Ls; makes for easier vacuum hose routing, component replacement, and I may even try the MAF from the old one on the new one to see if that's the cause of my poor MPGs. The one with the normal MPGs won't pass smog test because of lean codes of which I cannot find the source. Now, though, I have a slew of new troubleshooting steps to perform.
When I did the leak test with propane, I could pull a vacuum line and hook the propane hose fully into the opening and the car wouldn't even shudder. Is this a symptom of something?
-Tom