knocking sound

There could be a number of issues. Look into the following: >Incorrect grade of fuel (I know its retarded but cannot be left out :\) >Ignition timing incorrect >Fuel Injection System Faulty >Improper or damaged spark plugs or wires >EGR Valve not functioning >Vacuum Leak >Knock Sensor Malfunction Hope this helps!

Thanks! I had an in depth conversation with the tech about all of this and he said that the noise I hear is really normal. It is part of the emission system and it is something creating a vacuum in the fuel line to check that the appropriate amount of fuel is being used (that I don't have a leak). He said it is intermittent b/c it checks it at intervals..and that I would hear it longer when the tank is low b/c it takes longer to check (maybe b/c it is creating a vacuum) and that it doesn't start performing the test until the car is warm...of course I am paraphrasing all of this from memory. I have never heard of this but it matched exactly what I hear. Have you heard of it?

Depends on how loud the knocking is. I should have asked you that first, but I was in a hurry to get outta work :\ If it is almost un-noticable unless your actually listening for it, then that could be the case. If it is very distinct and can be heard easily, then you might want to look into the afore mentioned issues. Hey glad to be of help! Was I helpful at all? return the favor and give me some stars!

The loudness level comes and goes...I don't hear it often but when I do it catches my attention. But I am usually on a quiet street, stopped when I do hear it. I will make sure to bring it up again with your list of possibilities at my next service appt. thank you!

You have been very helpful, unfortunately I am a newbie here and I don't have any whole points to award...I would if I could :-)

Bah, no worries! Glad to be of assistance! Hope you dont have anything seriously wrong with your car.. VW's are very problematic vehicles. Good luck!