When my AOS went, I had lots of oil and smoke. It ran awful. It failed in my neighborhood and ingested so much oil that it fried my cats. I’d check that first. See if you can remove the oil cap with the motor on, but try not to run it much. Let me know how that goes, happy to help.

Another thing to add, my brand new AOS failed after about two months so if it’s relatively new I’d still be curious about it.
What’s the car and mileage?

Could def be AOS, as that can also cause the P0456 error code I was getting intermittently over the past few months. It's smoked occasionally on startup from cold but nothing like this, this was next level. Thankfully I wasn't far from home.

I haven't opened it up to check hose fittings. The last time I had 0456 code one of the hoses was loose so easy enough. But all the misfire codes (for all cylinders) leads me to believe it's not the charcoal canister anymore...but what do I know...

The spark plugs are pretty new (2 years old max) so I'd hope it's not that. AOS seems like a likely culprit, but to your point I don't want to run the engine if I don't have to; probably just have it towed to my indie :(

2004 Boxster S. Mileage is 74K

If you had said there was no smoke I would be leaning towards a vacuum leak, but the smoke to me is either AOS or something more serious. I never got any engine lights when mine went even though it ran horribly. The quickest way to test it though is the oil cap removal. It could offer some peace of mind if it’s very difficult to remove it with the motor on

Keep me posted

Thanks, I don't want to run the engine cause I'm afraid it's going to brick or blow up or fry the cats.

When I first got the P0456 minor evap leak warning, I tried removing the oil cap with the motor running and it seemed to come off pretty easily. So that makes me worried it's beyond AOS, but I just don't know. Going to have it towed to local indy, fingers crossed!

Update - also leaking oil - wonderful

Do you know where it’s leaking from? And how much?

Apparently the rear main seal (not good) and the "intake" according to the mechanic. Not sure what he means by intake. Like air intake? Don't follow that one. Rear main seal alone is bad enough. The bizarre thing is that I just had it up on a rack a month ago, and there was zero leak. The other bizarre thing is the oil was changed 2 months ago.

When the AOS fails it can flood the intake with oil (its job is to keep the oil out).

A leaking RMS is a different story though.

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Rear main seal isn't going to cause flashing CEL. AOS may but that's pretty severe.

Confirmed that the AOS failed and flooded intake with oil. Hopefully RMS isn't also implicated. We'll see what it looks like to fix

The oil leak could be the oil dripping all the way down the drain in your airbox, assuming you still have it. That’s what happened with mine as well. Hopefully it’s not the rms leaking.

Also not to frighten you, but my cats did get fried from the oil consumption and I needed to change my plugs afterwards, but again hopefully that’s not the case for you.

The indy's story keeps changing. They confirmed AOS failed and sent oil all over the place. But they go, "...but [AOS] has not failed externally (???) - the top of the engine is dry so most likely the leak from the bell housing is the rear main seal...

Thoughts on whether they'd both randomly fail at the same time? There was never leaking oil until the other day

Thanks!

Also, ecp - how long were you driving around after your AOS failed? Thanks. Want to know if I should expect cats to be toast, etc.

Do you trust this shop? There’s an internal diaphragm that fails and that’s when it starts shooting oil into the intake. On the outside it’ll look fine. Have you seen the leak from the bell housing with your own eyes? I’ve never heard of them both failing at the same time.

I want to trust shops, but I’ve been burned many times, so I’m wary.

I drove for maybe two minutes after it failed because I was so close to home and didn’t want the tow, or to push it since it was late at night.

I don't trust them that much. First off all, they nickel and dime. I only had it towed there because AAA will tow within 5 mile radius. I didn't go back to them cause I wanted to.

I think I'll just have them handle AOS and then have it inspected elsewhere... just hope I'm right!

Honestly I’d recommend doing the AOS yourself if you’re mechanically inclined. If you don’t trust them, I wouldn’t trust them to clean the oil out of the runners. If they don’t do that it’ll continue to seem like something is wrong, possibly damage the cats more, and keep smoking.

So say they replace the aos and it keeps burning up the oil in there and they say “it’s still not running right we need to keep looking around”, then what?

Ok get this - They said after replacing the AOS there wer still misfire codes, did a smoke test and found smoke coming from the bell housing/RMS. "It would appear that when the AOS failed it caused so much vaccuum in the motor that iit sucked the RMS inward and now you ahve a massive crankcase intake leak."

Like, first of all, I'm going to tell them to park the car until I figure out what's going on but like is that even possible?? I guess it's possible but is it likely? I'm at the point where the car is old, enough money has already been put into it and I don't know if it's worth it to keep putting a couple grand more into it. Saddens me but it's the truth.

I feel like maybe the RMS was the only failure? Canthe AOS fail possibly do that?

I’ve never heard of that happening, but it does sound plausible. Ultimately that would be your choice to make, but if it was my car I’d have it towed back home and start pulling the tranny.

Has the rms ever been replaced?

Jake Raby has said there are two modes of failure of the AOS. One pulls oil into the intake (most common) In the second the diaphragm fails in the opposite manner and pulls up to 24" water vacuum on the crankcase. This is the most severe mode of failure. Can cause low oil pressure and cause main seals failure.

Found the thread: http://986forum.com/forums/performance-technical-chat/21752-looks-like-aos-but-engine-woes.html

Thanks for this. Great, so mine is probably the more severe mode of failure. Wonderful. Sounds like pretty much everything can be damaged here.