Hi, I have a 2000 A6 with the 4.2 engine in it.Started running really bad yesterday, missing. Got home and ran the scanner on it for the check engine light it blinking on and off. showed three cylinders were misfiring.Checked under the hood and there is a round plastic vacuum valve at the rear of the engine right behind the manifold. It's sucking air like craze.Appears to have a small vent on the top where all the sucking is taking place.Large 3/4" vacuum hoses go to it.I believe it may go the the transmission.Can anyone tell me more about this valve? Looks easy to replace but I'm not really sure that is the whole problem. Ken

 

Hi Cardiffkid,

Are you able to take a photo of the hose and post it? It can make it easier for others to help with the diagnosis. My car is a 2.7T and not a 4.2 like yours.

 

sure I'll do that

 

You may find some imformation on the 4.2L engine on an A8 site:
www.audipages.com/Tech_Articles.html

 

Most likely a vacuum line to the secondary air system.
Thing is if one line has failed, all of you others are shot as well. Just go to ecstuning.com and order up the braided vacuum line. Remove and replace them one at a time 6-7 feet should cover it but get a little extra. It's an easy job, nice for a Saturday morning, just take your time.