jonesdds

2007 Boxster S, 60K miles, I'm the second owner bought used about a year and a half ago with 55K miles, local Santa Barbara, CA car. Car gets driven 2-3 times per week, short trips mostly. Checked out good with a PPI and has been serviced regularly by Schneider Autohaus in Santa Barbara, CA, a well respected shop. I'd also talked to them and they felt it was a good trouble free car, they'd done most service since new.

Many month later I noticed some fairly heavy smoke on start up, just for 60 seconds or so. This only happens under very specific circumstances. Only when I've moved the car when cold to say a difference place in the driveway or on street. So started cold and parked cold. It only smokes when it's started again after doing this. Never on cold or warm start. Never seen any smoke on deceleration at higher revs, even had friend behind me and they said none. Smoke is grey/bluish so would indicate oil.

Had in for service-use another shop for the simpler services on this car-he felt it would have to be the valve guides wearing allowing oil into the cylinders and not burning clean on cold startup. Could be true but then why wouldn't it smoke every cold startup. Does starting and turning off cold create a situation where the oil could more easily get into the cylinders? I'm not understanding how that could be. Also, at 60K miles seems awful early to be seeing valve guide wear.

I'm using 5w/40 total recommended by Schneider instead of the 0W/40. It's had it most if not all it's life.

Car might have been doing it when I bought it, no idea. Typically I don't turn off cold, just get in and drive to warm so it could have been months before the scenario occurred that caused it.

Any thoughts? Is there something else that can be causing this?

Anker

It a common issue and not something to worry unduly about. It is not caused by valve lifter leaks. As long as it only does it when started cold it is not an issue. If it starts smoking when started worm it is probably a bad AOS.

To put you mind at rest try removing the oil filler cap with the car idling warm. If it is hard or impossible to unscrew you probably have a bad AOS. If it unscrews easily you are good. Even better, test it with a manometer.

Every now and then I get smoky exhaust on my 2004 S, but only on cold starts.

jonesdds

AOS=?

Macster

The something else is just an AOS (air oil separator) that is performing sub-par. It doesn't even have to be bad or failing. My experience over the years is once in awhile, most often after a short trip -- which my Boxster seldom experiences -- but even after a longer trip and the engine is shut down the next time the engine is started, from cold, the engine can smoke a bit.

And my experience over the years, and with 3 bad AOS's, is a bad or failing AOS will have the engine smoke at cold start and continue to smoke. The engine can even begin to smoke when up to temperature.

The brief engine run time when you move the car around is just the type of usage that increases the chances the engine will smoke upon the next start.

Porsche techs encounter this smoking upon cold start all the time when they go to get a customer's car to bring it into the bay for service or start the engine of a new car. The techs tell me that as long as the smoking is short lived, the engine manifests no untoward behavior, and the CEL remains dark they don't worry about it.

If in the case of your car if the smoking persists, or occurs after a hot engine start, if the idle goes up and down some, or the CEL comes on, the smoking is probably a sign of something amiss. Most often -- I've been through this 3 times now with my 2002 Boxster -- it is the AOS. Well, for my Boxster engine it has *always* been the AOS. If you suspect the AOS my advice is to ASAP and when safe to shut off the engine and arrange to have the car towed (flat bedded) to a shop for a professional's diagnosis. An engine can "recover" from a failed AOS with no real trouble -- mine has recovered 3 times with nothing more than just some drive time -- but there is a risk of continuing to run the engine with a suspected AOS and that is the engine can suffer a hydraulic lock up due to the volume of engine oil the AOS is allowing to pass through into the intake manifold.

mikefocke

A list of Porsche related Acronyms I've come across in my 10 years on the forums is here.

jonesdds

Thanks all for the help with this. I tried the test Anker suggested. I was able to unscrew the cap and remove slightly, definitely a vacuum and increase in idle when lifted off slightly. I assume that's normal?

I've had two incidents of the CEL going on(I'm getting the acronyms!) in the last 3-4 months. One was checked at it showed as some kind of vapor leak I think is how the mechanic put it. Nothing until recently came on, tightened the gas cap and restarted and was off. Gas cap didn't seem real loose so not sure really the issue but hasn't come on since.

Definitely only getting smoke on start up when cold and only when I'd last shut it down after running just a couple minutes. How big of a job is replacing the AOS? Everything obviously hard to get to so probably not doable for me but wondering.

Anker

Yes, that's perfectly normal. I think you are fine!

Macster

Years ago, back in early 2004, I accidently stumbled on this oil tube filler cap "test". I may not have been the first but I was not aware of it as I was investigating what would prove to be the 1st of 3 AOS failures over the years.

In my experience while I could unscrew the cap just fine I was unable to remove it against the pressure difference. Normally one can lift the cap off with no real difficulty. The engine will react/stumble but the DME will adapt pretty quickly. When you put the cap back on the engine's reaction is not quite as dramatic but as before the DME will adapt pretty quickly.

That you can lift the cap off with no real effort is a good sign but the cap being hard/impossible to remove is a later stage failure symptom/sign. It was shortly after I found I was unable to remove the cap that the engine began to smoke all the time.

Whenever the CEL comes on it is important to read the active code (or codes -- there can be more than one code active), check for any pending codes, and then get the freeze frame data which will include the specific code that triggered the freeze frame data capture.

Write all of this down.

Given the engine only smokes upon cold start after the engine is run only a short time and there are no other symptoms I believe the AOS is in the clear. While the car does have 60K miles and that's getting close to the miles when AOS failure is more likely to be a problem (my experience is AOS's last anywhere from around 80K miles to over 100K miles given my usage) replacing the AOS I think would be premature at this point.

However, it is your car and if you want to replace the AOS now that's your call. I have no experience replacing these. All have been replaced at a dealer. I don't even recall the price now. There are write ups on how to do this if you want to tackle this yourself.

Just a heads up. While my Boxster has been through 3 AOS's it has also required 2 new oil tube filler caps and one gas cap. After so many miles, uses, these wear out and leak. (Although while the gas cap appeared to be vapor tight the tether broke. After I had the new cap installed and could then look at the old cap it was clear while the cap was still vapor tight it was on the brink of leaking given the condition of the seal.)

extanker

some times hot
some times cold
some times alot
some times not
nature of the beast and embarrassing BUT if yours is doing it for 60 seconds you have issues with some thing

Schnell Gelb

A digital manometer is $20 Pyle on Amazon. Essential M96 diagnostic tool

jscott82

I'm new to the water cooled crowd... But can say it was normal on the air cooled cars, and the issue is the layout of the motor, so not surprised it still around.

The issue is the flat (horizontal) layout of the cylinders. Any oil that is left clinging to the cylinder walls on shutdown will run down and pool on the side of the cylinder. When engine is restarted you have a puddle of liquid oil that has to burn off. This does not happen in a V or vertical inline engine.

I assume its happening only after a cold shutdown because the rings have not fully seated, and are leaving a heavier coating of oil on the walls.

Quadcammer

I disagree. 60 seconds of oil smoke is nowhere near normal. A few big puffs right at cold start up, ok (although I rarely if ever get that), but a full minute of continuous oil smoke points to a bigger issue.

Macster

Yes, "60" seconds of smoking is not normal. It was not clear to me -- and I didn't follow up with the OP -- that the engine was truly smoking for 60 seconds or the cloud of smoke was just hanging around or water vapor was being mistaken for "smoke".

And just a comment: The engine layout is not the reason for the smoking. If the AOS is bad (or good) the cause of the smoking is the AOS. It fails to remove all oil vapor from the crankcase fumes and this vapor passes through it and hits the intake wall. There is becomes a liquid again. If the engine up to temperature and continues to run this oil gets burned and there is no smoking. If the engine is cold or shut down, the oil will then be burned at the next start up and if the engine is cold the oil will smoke.

When the engine is shut off some oil remains in the bottom of the cylinder, that is the portion of the cylinder that the piston leaves exposed. The oil though will not flow into the combustion chamber. The chamber is hot and oil flows away from heat. Additionally the there is an oil control ring and two compression rings. Even with just the ring tension these press against the cylinder wall with enough force and there is sufficient contact that no oil will flow between the ring and the cylinder wall. The oil somehow flowing between the ring and the ring groove around behind the ring than down the other side between the ring ring groove and on to the next ring and a duplicate of this route is just not going to happen.

jscott82

I missed the 60 sec part, and agree that's not right...

jonesdds

I think I misspoke on the time it smokes. It's maybe 15 sec just takes a minute or two for the smoke to dissipate.

Again, it only does this on cold start when shut down cold.

Biggest problem right now is it's covered in ash from our awful fires- It's in SB and I've been out of town.....