Burst of Blue Smoke

[Bradster]

On occasion, and usually when I start the car cold, I'll get a burst of blue smoke. After the initial burst, it goes away and it may be ten starts before it happens again. No smoke while running. Again, this happens only occasionally. I assume that bit of oil is getting by the rings, but why only once in a while? Any ideas?

Thanks. 97 Boxster, 79,000 trouble free miles (so far)

Bradster

[Lobo1186]

possibly failing AOS. there are many threads on how to check and it can be a DIY but dirty. the part is around 96 dollars last time i checked.

[ChrisZang]

I think that's normal
I heard that it's a "flat-6 disease" and there's nothing you can do about it

[jcb986]

I think that's normal
I heard that it's a "flat-6 disease" and there's nothing you can do about it

I don't think so...these engines are just incredible. The AOS could be a problem or something else. I suggest Renntech.org site, it is run by Sunset Imports, I see a lot more engines questions on their site. Also, you could querry the forum here.

[ARModen]

It seems to be a pretty common observation. There are lots of threads on it. My '99 does it at least once a month, and it's got 120K miles on it. The consensus is that it's either an AOS that's not 100% effective anymore or just a product of engine design. I think if the AOS is failing we'd see the smoke more consistently.

One of the other older wiser guys suggested that because the cylinders lay flat and are so low in the engine, oil tends to settle out where it can leak into the cylinders. In a normal car the heads are on top, followed by the valves and pistons. The oil drains down and away from them when the car cools. In a Porsche this doesn't happen.

My personal theory is that there is something (piston ring, valve guide, etc) on one cylinder that leaks as the car cools, but only when the crankshaft is in one specific position. Which is why we only see it once in every 6-10 starts. Someone ought to do a science project and log their crank angle every start to see if they're related.

[boxzilla]

My input would be that this is a common observation esp. if the car has been sitting for some time. From what I read, this is due to the design of the engine. If you had an AOS issue your idle would be very erratic (esp at idle) My 2001 does the same thing and with 70k miles on it, I plan on replacing it sooner than later but consider the blue puff of smoke a "feature" ...lol I am watching my oil consumption, and watching for smoke at times other than startup, and watching my tach for indications of AOS failure.

[Covelo]

I think it's a boxer engine issue. My 1972 VW bus does it occasionally and my BMW R65 used to too. My Boxster has not so far.

[Bradster]

Thanks, everyone! I appreciate the input.