AOS changed - smoke from left exhaust - bore scoring?

Now here's a question to engine gurus - before I either do that borescope test myself or take it to a specialist any possible ideas what could be wrong here. Background - changed AOS etc about 1-2 weeks ago - also updated fuel pump, cleaned intake manifolds (just paper - not with any special detergent), cleaned both TB and MAF and did an oil change. After everything there was just a minor faint smoke coming from both exhaust. Yesterday when the engine was warm I added 0.25ltr oil because both dipstick and dashboard showed that it was like 40% full - just a little bit below half point so decided to add that 0.25 ltr there. Next morning there was again a lot of smoke coming from the left exhaust - as so was today. I did warm that engine night before that so it's not about starting and stopping the engine before it's warm. I did a few days ago manometer test and based on that AOS should be fine - I got 5.4 InH2O - unless it broke somehow now. Ideas? Cold start Warm engine

Why was the AOS get changed? Did it fail...i.e. tons of smoke out of the tailpipes or just readings out of spec? Not sure that I hear what might be bore score ticking. No expert here only knowledge was from my experience. To get a good recording place the phone below the headers on the passenger side and record maybe 20-30 secs without moving around. Do the same on the drivers side. You mentioned the night before you "warmed the car up before shutting it down". You didn't let it just sit and idle to warm up...right?

Only smoking out of one side when cold or all the time now?

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I changed AOS because the AOS bellow was worn out / broken so I decided to replace the whole thing - tested with oil cap test and the engine almost choke when I removed the cap. Now it is - or should be - working fine - tested a few days ago.

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It's only smoking after cold start - it is not smoking at all after it's warm as can be seen from that video. Tried again after the car has been sitting in the garage for two hours and it's still fine - no smoke at all.

When I had white smoke (i.e coolant) out of one tailpipe, it ended up being a cracked cylinder, but it was smoking all the time. Maybe a small crack in the bank 2 head that's sealed up once at temperature.

Ok - here's another video underneath the car when the engine is warm. You Tube

If that is smoke and not moisture boiling off then you have oil in the cylinders right bank looking from rear, and I believe those include pistons 5 and 6 which are the ones most susceptible to borescoring. Also I think oil could leak from the valve guides but much less likely.

Couple of new observations - that coolant reservoir cap was quite tough to open as there was quite high pressure inside - normal? I'm under impression that there's a valve that controls possible overpressure. Tested AOS again with manometer and it was 5.2 InH2O so AOS is ok. Oil level seems to be one level from max (dash) and a few mm from max on dipstick which is a bit surprising since day before yesterday it was just below halfway before I added that 0.25ltr even when the engine was warm. Looks like there a difference between warm and "warm" - seems that about 20km ride is not even closely enough to rise the oil temp to a appropriate level in this weather (about +- 0C). I'm getting paranoid here - somehow the ride quality dropped today after did about 50km on freeway. Earlier in the morning the engine sound was quite soft with a somehow an almost like a EV car sound when accelerating - I was thinking that that engine sounds so good even if there's some issue - now that "EV sound" disappeared but there's some kind typical - I can't describe that sound but I have heard that before on some other cars - but not with this one ever before Tip so far has been really smooth without any sound. Not sure if that is coming from transmission (tip). It's kind of a whiz or whine especially when you lift your foot from the pedal and let the car coast before intersection for example.

Do NOT measure the oil when warm after running the car even though that is what the book says. Measure the oil engine cold(before first start of the day) on a flat surface. It takes a while for the oil to drain back to the pan. Measuring warm and adding oil based on that measurement to full you will end up over filling the engine which is not good. My engine guy says fill engine to 1/2 full then add oil when it reaches the low level on the stick(when engine is cold). Then add only enough oil to bring it back to 1/2 full. Water cap should be hard to loosen as it should be put on TIGHT! May not have been pressure.

I didn't see you verified it was smoke coming out of the left tailpipe and for sure not water vapor? We have a Ford pick up and a vapor would come out of the exhaust and it was the head gasket went bad, there was a leak between the combustion chamber and coolant jacket and coolant would get into the cylinder and vaporize into steam.

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I don't think it's water vapor - it smells like a ... well, exhaust. Coolant level stays constant so I doubt there's some intermix between coolant and combustion/oil etc.

You've put to much oil in. Use the dipstick when the oil is cold. Keep it halfway between the dots.

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Ok, I was thinking about that as well because somehow that coincides with the time when I added that 0.25ltr but then again how is it possible that day before yesterday when the engine was warm both dipstick and dash showed that it was like 40% - both well below halfpoint. I added 0.25ltr which should be about one notch in dash and "a little bit on the dipstick". Also now when the engine was most likely hot it (and oil expanded to the maximum due to temperature) it's still below the max level (both dipstick and dash). ps. I just removed oil filter to remove that extra oil a bit.

Question for the collective brain trust........after replacing a “blown” AOS how long does it typically take to”burn off” oil that is throughout the intake manifolds mufflers catalysts etc?

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Depends on how much oil was there in the first place, and whether you cleaned as much out as you could.

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so I have a 99� 911 making the exact same noise your car is making. What did this turn out to be? Bore scoring? Also, my car is not smoking. thanks so much

Yes, unfortunately it's bore scoring.