sonata54

I have just reached 150k miles on my 2000 A8 and for the past 10k or so i have noticed the smell of burning oil, the smell is stronger when it's cold out. When I take off my oil cap after driving there is vapor(or oil smoke) that is coming out everytime. I recently had a timing chain tensioner go out and had it replaced. Also last year I had many intermittent misfire codes in which I would get a check engine light at high speeds(65-75 mph). These codes have not shown up for the past 8 months though, they just stopped showing up. If I sit idle for a few minutes I notice that the car vibrates and shakes a small amount.

What could be causing the burning oil?

silverd2

Probably vapor...smoke from inside the engine is not likely.
The vapor is normally burned in all engines through the PCV (positive crankcase ventilation) valve. It get sucked into the intake through this valve. With the engine off, the vapor has no choice to but to drift out the filler cap when removed. If it blows vapor out of the cap at idle when removed, then maybe the valve is failed or clogged vent hoses (1 across front of engine & 2 others that connect under the rear of the intake manifold)...total failure of this system would not "directly" cause oil smoke, but in some cases can make oil leaks, esp valve covers, more likely...due to unreleased pressure in the crankcase.

When they replaced your cam chain tensioner, the valve cover had to come off on that side...replacing the valve cover (with no leaks)is precise procedure, requiring special care and some sealant in the right places...otherwise a leak will occur in short order. This could likely leak oil directly onto the exhaust manifold directly below the valve cover.

Past misfires are likely unrelated to any smell...could have even been a timing jump (causes random misfires) related to your failing tensioner or even jumped belt timing, which all should have been corrected (if off) during tensioner replacement.

Check the exhaust manifolds (look with flashlight if needed) when engine is hot and preferably idling, for signs of oil leaking onto them and burning.

Rough idle might not be related(?) ...might be(?) ...for that I would check the spark plugs, unless very new AND run Techron (in particular...others don't come close) injector cleaner through the tank once or twice...could just need a fuel system clean.

Another VERY common problem with all D2 (maybe later?) A8/S8's, that causes an oil burning smell (pretty stinky, almost like rubber burning) is the drive shaft output flange seal, directly above the left (driver's side) catalytic convertor. It leaks gear oil from the center (Torsen) differential directly onto that cat. My car ('01 A8)is on it's third seal here...I put in the third one (replaced twice since new)at under 100K miles.
Easy to check, look under the car at that cat for any oil at all on it...if it's wet or see signs it been burning there....that's probably your smell.

sonata54

Cheers to that through response there, I will check those seals and the exaust manifold as well as run techron through my threads, doesn't look like those plugs have been replaced since the car was manufactured. I shall post my results within the the next week or so. Thanks SilverD2

pocketchange

I'd befriend someone that knows their way around an A8 and go in for a major tune-up.
Plugs, plug wires, valve cover gaskets, cam plug seals and if you have not replaced the timing belt in the last five years (that too), along with ALL the seals, idlers and tensioners and water pump. Then, a look at the subframe bushings, motor & transmission mounts and the condition of all of the suspension and everything else that bumps, squeaks and wears out.

Call it therapy.

Hey.. It's only money if you enjoy your Audi, or you could get a new A8.

pc

silverd2

A little over the top for some...changing gaskets and seals that aren't leaking?

...I just fix what's wrong.

...but, "plug wires"? ...what plug wires? ...no plug wires in an A8 or other cars with individual coils...nothing goes wrong (no wear on) with the small signal wires leading to the coils...no more current than a dash light.