lyleswk

Again, I haven't had this issue and have not tried to figure out if my SAI pump is working, so I'm no help there. As far as hoses, usually a simple visual will tell you.

As far as how this affects the way the car runs, it unfortunately totally depends on the severity of the problem. Since your car sounds like it is running okay, my guess would be a small leak that the car senses or maybe the combi valve that is slow to open / close. Any of this can cause a lean / rich running condition which will show up in the O2 sensors which would throw the code you started with.

Don't worry, once you get this figured out, you won't have the annoying CEL staring at you.

Bad cats: Generally, you will not notice anything for a while. You will only be spewing more than "acceptable" levels of the NOx into the atmosphere. Eventually, most cats will come apart and then you have a partially / totally blocked exhaust and you will notice that quickly.
Bad vacuum hoses: Depending on severity, nothing to really poor running.
Bad SAI: First an explanation. SAI puts fresh air into the exhaust prior to the cat to attempt to further combust the gasses to reduce NOxs. It has been around since the 60's. So, if it is not working and depending on the efficiency of your cat, you may not meet emission standards. So again, this will result in more emissions.
Bad O2 sensor: Not sure about effect on running becuase I think ECUs generally go into a default fuel air misture if they are failed, but it certainly will effect the ability of your car to run as leanly as possible as it is one of the primary sensors the ECU uses to adjust the fuel / air mixture for optimum emissions.

So, you see the thread with everything aimed at emissions and why you didn't get a permanent inspection sticker. Bottom line, everyone thinks fixing this stuff should be easy, i.e. the codes will point directly to the problem, when they really just point to the system and there is sometimes some luck involved in finding the issue.

A84Nate

Looking at my car today, I noticed the paint looked rather odd along the edge of the rear right wheel arch. Upon closer inspection I noticed the paint was bubbling/cracking due to rust underneath. Man, does it ever stop with this car! New tires, CEL, oil sensor, now rust that I'm sure won't be covered under the corrosion warranty. Maybe I should just sell it now and start looking for another 5-series from California or Arizona.

lyleswk

That is probably a crappy repair job.

Did you have a chance to look at your SAI?

A84Nate

No I haven't, because I don't know how to find it or what it looks like. I admit that when it comes to working on cars, I'm about as useful as a knife at a gun fight. My father and brother are pretty good at it though but even they were afraid to tear into all the plastic covering. We tried looking for a damaged vacuum hose but couldn't single anything out really. We did find a lot of braided hoses that had frayed ends however.

I noticed another little thing that likely isn't a problem but I thought I would mention it anyways incase someone knows. When the interior ventilation system is on and the fan speed is high, I hear this low pitch hum coming from inside the dash. As the fan speed decreases, the noise goes away. There is no ticking and the motors that change the air flow from foot > facia vents > defrost seem to work fine. Should I be worried about a motor burning out?

Despite these issues, I REALLY want to love this car! It's raining this morning and the temp is in the mid 40's so for someone who doesn't like to be wet or cold, this weather takes the biscuit. But I get in the Audi, it starts right up, I turn the heated seats on '3', and off I go. Warm air was already blowing not even two blocks later and the quattro sure feels stable on wet roads. This is a great cold weather car.

lyleswk

1) Here is a link to a picture of one. On the V6, I undestand it is on the bottom of the engine bay (will have to remove the bottom cover to see it) on the passenger side. You will see the pump with a line going to the top of the engine. The other should go to the airbox where the air filter is. On the 1.8, the filter is inside the airbox which is just in front of the passenger wheel. I assume it is the same on the 3.0.

http://www.ecstuning.com/Audi-B6_A4-...ondary/ES3279/

2) I think all the whirring you hear is normal...or at least mine does it. It is a fairly noisy HVAC system in my opinion.

A84Nate

Got the call from my mechanic today letting me know my car is fixed. Turns out Lyle was right, it was the SAI that was the problem. I'm so relieved I don't have to pay for this; the part alone was around $500 when I looked it up. I also got them to tinker with the headlights so the beam throw goes out farther. Now I can see objects 100ft away instead of just 10ft away. That's one thing checked off my list of TLC items for my beloved but tempermental Audi.

Next it's:
Full TB job
power steering fix
horn replacement
windsheild washer pump replacement
rust area refinish
and the little plastic faceplate the attaches to the small storage box next to the ESP button