Jkay

Kind of odd ... once every ~20 start-ups, my 99 A8 puffs a cloud of blue oil smoke out of tailpipe .. the OTHER 19 start-ups are clean and puff-free.

Ideas?? 48k miles, and running perfectly otherwise.

PaulW

If you start the car when it's cold, then pull it out of the garage and park it to wash it or something, then restart it at some time later, it will puff smoke.

That's because it's running it very rich when it is cold (even if it's 70F) for the first minute of operation.

Then it has all the unburnt stuff in the combustion chamber and you restart it in an hour or 4 later and get the puff.

I've noticed that with my car when I move it from one side of the street to the other and turn it off right away.

Other's with S8's have had the same problem, but it was determined that it was less than a 30 second run when it was cold followed by a start sometime later.

pw

ryoung

When the car sits, oil that has been pumped up to the valve train can puddle around the valve stems seals, leak by the seals, and get into the combustion chamber. With a bit of oil there on start-up, you get a puff of blue smoke from the oil burning. Usually the longer the car sits, the more likely you are to get a puff of smoke.

Though this is a bit annoying, it's not a big deal or that uncommom. You can go years with valve stem seals leaking like this and have no noticeable oil consumption.

hisport

As Randy says, if it ain't using oil, no worries.

Some cars just seem to do this; new or old. My '99 A8 does it once in a while, after sitting in the garage for a while. But doesn't seem to use any oil at all.

ryoung

my Saab 900 did this, and it never required topping up with oil between changes. The car finally died of a rusted frame.

Jkay

Thanks for all the replies -

It happens exclusively during cold starts, and it does not use oil.

I figured it was fine, but was hoping for a "yeah that happens to all A8s" answer.

I'll keep an eye on the oil use. It never blows clouds during acceleration so I'm pretty sure it's not serious.

skiwi

normally with the valve stem seals you will notice blue smoke on overrun...

$0.02

ryoung

I assume you don't mean overrev, which is impossible with the TIP.

hisport

Overrun: Coasting in gear; eg, gearing down and using engine braking, as in approaching a corner.

This is an Angloism, mate. And which skiwi can't tell you 'imself, guv, as he's likely buggered off to bed, being a bloody Kiwi, for all love.

BTW, you will generally see the highest manifold vacuum on overrun, especially down a hill. If you have worn valve guides/rings, oil gets drawn into the combustion chambers and burned (with a blue puff/cloud) when you reapply the gas. A really worn engine will smoke when moving away after sitting at idle; same phenomenom.

PaulW

I never knew the DP caused by the vacuum is what caused that -- Thanks for the Info!