Pat

Once in a while I see a small puff of smoke at start up. I understand this is normal. However, today, at the track, I started the car and a LOT of smoke poured from the exhaust. So much so, that a couple people came running with fire extinguishers. It lasted a couple minutes, so I shut it down and let it sit. An hour later, I fired it up again and more smoke came out, but maybe just half as much. Still, it was what I would consider a lot, and I decided not to go on track for fear of something being wrong and dropping oil on the track. I let it sit another hour, fired it up and a little bit came out as I drove through the paddock to the highway. I drove the car 30 minutes, shut it down and went inside for a burger. When I came out I checked the oil, which was at the maximum mark, just like yesterday. I started the car, and there was zero smoke. I drove home, let the car sit a little bit, and the oil is still at the max mark.
Based on all of this, it seems to me like I just had oil settling in the cylinders. But it seems like there was a LOT of oil in the cylinders. Has anyone else experienced this? The car has a perfect maintenance record and has not given me any problems in my four short months of ownership.
FWIW, after my last session on the track I shut the car off without letting it cool down first. Not sure if that had anything to do with it, though.
Any thoughts?

nosnow

Sounds like your air oil seperator failed and you are getting oil into the intake, you will probably want to fix it before driving as you might hydroloc the engine with oil.

Macster

You should always take a cool down lap before shutting off the engine. Or let the engine idle -- with A/C on (runs the fans constantly) a few minutes to let at least the engine shed the heat load track driving causes.

The smoking may be an AOS. I would think the smoking would appear at every engine start and persist. However, the couple of times my car's AOS failed and got to the smoking stage I never dared experiement to see if the smoking would diminish and disappear after one or more subsequent engine starts.

What might have happened is you overwhelmed the AOS with oil vapor from your track driving. If the oil level too high, the oil not fresh (or the wrong kind, viscosity) this can add to the oil vapor load the AOS has to deal with.

The result is the AOS allows oil vapor to pass into the intake manifold where this oil vapor collects on the intake runner walls. If you shut off the engine this oil will drain into the chambers where upon the next engine start it will cause smoking.

Not all the oil runs into the engine right away and this oil can take some engine run time to remove. In short the smoking could have been this intake runner oil slowly making its way into the engine where it was burned and caused the smoking.

That the engine oil level didn't drop from the smoking is another sign the AOS is probably (probably) not failing and thus is not the cause of the smoking.

The absence of any other AOS symptoms (hunting idle, hesitation off idle) or a CEL does point away from the AOS as being the cause of the smoking.

But you really want to have the AOS checked out by a qualified tech just to be safe. And keep an eye out for any symptoms that point to the AOS starting to fail.

Sincerely,

Macster.

Pat

Follow up:
The car runs perfectly now. No smoke, stutter, warning lights, etc. It seem so me like the oil that got in the intake maybe just "sloshed" in there from the track driving, as the oil was at the max mark. The only was one week old. It seem to me it was burned off on the drive home (highway for an hour) and it runs just fine now. Is this surprising?
Also, I just took the oil cap off while the engine was running. There was a bit of vacuum, but taking the cap off was far from difficult. The idle got a bit funky with the cap off. I quickly put it back on and the idle returned to normal. No suprise there.
Your thoughts? Inspect the AOS, probably find nothing and continue enjoying the car?
Oh, after looking through the previous owner's records I saw the AOS was replaced three years/18K miles ago.

Pat

More follow up:
Just took some photos.
http://picasaweb.google.com/patmickelson55/AOS#

Macster

No oil sloshed into the AOS unless you got the car upside down. Track driving can put a lot of oil vapor in the crankcase fumes. So no, the smoking is not surprising. More than a few owners experiencing track driving have reported this. Some even have had the engine misfire and set the CEL or even enter limp home mode temporarily.

When you removed the oil filler tube cap the engine idle behaved correctly. Had you left the cap off longer the Ecu would have adapted and the idle would have returned to near normal, only to get funky again when you put the cap back on and as the Ecu unlearned the adaptation it learned when the cap was removed. Removing the cap represents a big intake air leak the mass of air of course not being measured by the MAF.

The AOS -- at 18K miles -- is probably not at fault. They can fail at any time, but in your car's case the AOS is probably ok. But if some failing AOS symptoms appear..., that probably ok turns into probably *not* ok.

But absent any more persistent smoking upon engine start and afterwards, any more signs of an AOS entering its final death throes, in the meantime just pay a bit more attention to the car's behavior, that is the engine's behavior for a while just in case the 18K AOS is experiencing premature failure.

Sincerely,

Macster.

Pat

HUGE thanks, Mr. Macster, sir. That's what I was fishing for, and actually believed was the case.
Anyone else care to contribute?