2003 A6 2.7 T...

120k miles, stock, no tune

All of a sudden smoke is pouring out the tail pipe.

got a check engine code a few weeks ago P0139 (O2 sensor, slow response)

Engine is down 2 quarts (no low oil lamp?)

It had been using a quart or so every 3000 miles, but now it's serious.

Any thoughts???

 

Wow, lots of fellow 2.7T owners posting problems lately.

One liter is pretty alarming on our engines. I use very little oil over the course of the 5000 mile service interval per oil change. Operating the car with two liters less than what it should have may result in serious damage to the engine and turbos.

I would look into a loss of compression in each cylinder that may indicate worn piston rings, and just to check the overall health of the engine. I think you may find that you have some internal issues that are causing the smoke out of the tail pipe and allow you to burn oil. I think it's a rare condition on this engine as I haven't really seen or heard about many people experiencing piston ring issues, but it's certainly not out of the realm of possibilities.

 

I'm thinking it's the turbos...

This came on pretty quick, the turbos always had a little blow-by, I would find a little at the inter-cooler

 

Oil in the intercoolers and piping leading to them was an important clue, I must say.

 

The saga continues

Checked the intercooler ducting, very little oil, I would say the normal teaspoon amount on each bank

Pulled the plugs, they are all rusty looking, it is using some coolant in addition to the oil.

Prior to this I had added an additional 2 quarts (4 total in the past several days)

The compression is 160 psi

I'd like to know where the oil is going

 

Did you check the compression of each cylinder, and do a wet and a dry compression test for each one? I ask because I only see one compression figure.

Does the oil in the crank case look milky?

 

All 6 cylinders are 160 psi, warm

oil doesn't look milky, hard to tell there is hardly much on the stick

 

Assuming the compression test turned out alright (wet and dry), and you have checked the oil (Probably either doing a full on oil change or extracting some using other methods) I would begin to suspect the turbos and the manner in which they are being fed oil. This is quite possibly the worst news a 2.7T owner can hear, I must say.

I forgot to ask, have you noticed a decrease in coolant?

 

coolant has been decreasing...

Not sure about wet/dry compression testing

 

Check your PCV valve and vacuum lines. I had the same issue two months ago and was terrified my turbos were blown. Turned out a vacuum line was busted and my pcv valve was clogged causing excess blow back and it to suck coolant. No idea how but once it was all taken care of and coolant and oil topped back off the car runs just fine. I have a CEL because of a fouled O2 sensor from it, but eh its not affecting performance any so I'll worry about it when the snow clears up.