davecheng

I have a 2001.5 S4, 85k miles on original turbos. APR 2+ everything, and preventative crap like bipipe, 710Ns, etc. The car has been babied for as long as I've owned it, if it means anything at all.

I swapped the cats out for <b>test pipes</b> a few days ago, and maybe it's just a coincidence, but I now notice <b>puffs of smoke</b> from the exhaust on <b>decel</b>, when the engine is in vacuum/overrun. The smoke is faintly blue, and smells of <b>burnt oil</b> (amongst other pollutants). It's only noticeable in <b>slow moving traffic</b>, or when <b>engine braking</b> to a stop in 2nd or 1st gear. (Engine in full vacuum/overrun state.)

Everything seems <b>fine under full throttle</b>. The car is still making full boost (about 16 psi) and good power. <b>No smoke at idle or on cold starts, either</b>. The turbos are whining faintly like police sirens in vacuum (and have been for a while), but under load, they're quiet -- no dentist drills here.

The valve cover gaskets, cam adjuster seals, and turbo oil return line gaskets were all replaced under warranty a few months ago before it expired. The car burns about <b>1L of oil every 5000 miles</b>. No coolant leaks.

Before I have this sucker torn apart, what the heck could be going on here? Would blown turbos be the cause of burning oil in <i>vacuum</i>? Maybe the problem has always been present, and I'm only noticing it now because it was previously hidden by the cats? Or maybe it has something to do with reduced backpressure of test pipes?

Help!

clinton c

But One quart of oil per 5000miles is nothing!
And turbo noise during Vaccum sounds VERY strange to me. Never heard that!

davecheng

the faint "police siren" in addition to normal spool is quite common. I've seen a few videos and sound clips around here with it...

Rcjustin

Did u ever find the cause of this? I just did a clutch job on my a6 2.7t and also did piggie pipes gutted both cats and now have the exact same symptoms as you had. What was the issue for you?