2002 996 C4: Bore Score, Valves or?
 

So my 2002 C4 cab 6-speed with 42k miles which I've had roughly 5 months continues to emit 2-5 seconds of white smoke from the left exhaust on nearly every cold start. Had PPI plus compression check and leakdown test before buying which all passed with flying colors but did not pick up on this problem which again only shows itself on cold start. Changed AOS a month ago which reduced oil consumption considerably (I've lost little or no oil in the 1k miles since), but the smoke continued. I've seen some rennlisters say that some smoke on a cold start which resolves quickly and without other symptoms is nothing to worry about, but it didn't seem normal so I brought it back to my local shop (franks motorcars in Laguna beach) to look again. Replacement AOS seems fine but plugs on the right side are oily when pulled. They say boroscope won't give a clear enough view for diagnosis, so they recommend pulling the engine to see if the problem is valves, cylinder scoring etc. They said if it's valves then we're looking at $3700 valve job, but if it's something more serious like so cylinder scoring , we are looking at a $7000 short block from Porsche, plus around $6000 in additional parts and labor, plus tack on another $800 or so if I want to throw in a new clutch (Around $14,000 and two weeks all in). By the way, I hear no clicking/tapping noise from the engine which I know can sometimes indicate cylinder scoring.

Aside from the money, it's a bummer to think that the previous owner probably had some idea about this problem and decided not to mention it. Anyway, I'd appreciate any thoughts and advice, as well as recommendations of any other shops in orange county CA which you feel would do the best job diagnosing and repairing this.

Thanks, Brad

No need to pull the motor yet. Scope from the top, then pull the oil pan and scope from the bottom. If your bores are scored, one of those will see it.

Yes I agree with gnat, it won't be valves if your getting smoke it will be a cylinder just remember which ever tailpipe you get the smoke from it will be the opposite bank you need to check as the exhaust passes from one side to the other so if you look at the rear of the car and the right tailpipe is smoking it's left bank 1-3 and if left is smoking it's right bank 4-6.
You can get smoke on cold start from condensation and also from cold fuel map settings but really you should see the same from both banks, if one is more than the other it could be a problem but this can be identified without getting committed by borescoping like gnat said, and it should be a relatively small cost , you could do it yourself if you have some knowhow especially from the bottom where you are most likely to see scoring as from the top it is often hidden by the piston itself as even at bottom dead centre the piston is still covering the bottom part of the cylinder.
Basically drain the oil and remove the sump plate, place the piston you want to look at on top dead centre and put the borescope in.
I'm sure others will chime in, post a video of the smoke if you can!

No CEL. No noises. No other symptoms. No signs of any engine trouble just a brief bit of smoke upon startup.

No problem.

Relax and enjoy the car.

"The plugs on one side oily" multiple oily plugs are less likely to be bore scoring then something else common to one side.
I tend to go with Macster, drive and enjoy it. At least until more symptoms show up.

As an aside, I have a, new to me, Turbo that randomly (hot, cold, sunny, cloudy) smokes a good puff on startup. I found that if I keep the oil between 1 & 2 bars low on the indicator it does not smoke on startup?? Turbos have a true dry sump engine so why would ~1/2 quart make a difference? I don't know and it is not going to stop me from enjoying the car.

My guess is the oil level has nothing to do with the smoking on startup. What you are probably seeing is from a leaking turbo seal.

Do you let the Turbo engine idle ~2 minutes before shutting it off?

The OP says all three plugs on the right side are oiled. Odd that all 3 are oily.
So logically the cause is common to the entire right side bank.
1. all 3 cylinders are scored/cracked - strange coincidence
2. all 3 have worn oval -ditto
3. all 3 have badly worn oil control rings, suddenly and simultaneously
4. all 3 have simultaneously worn valve stem oil seals or valve guides
And none of this was apparent in the PPI !
Weird.Sounds like my experience all over.
Time to visit Tony Callas at RennSport,Torrance for a diagnosis ?

Sorry, the smoking video is here:

From your video, in addition to the smoke, there's a really loud and bad knocking noise when the engine is cranking. I suggest not to drive it much until the problem is diagnosed.

I agree, I am more concerned about the brief knocking. It 'seems' as if it is slow to build sufficient pressure/volume to cushion a worn bearing or pump up something else.I am not going to speculate but I think many of us can guess.Which is exactly why you shouldn't listen to us -they are guesses!
Diagnosis is the most crucial and valuable part of this. Some can repair the M96, few can do the diagnosis as well as Rennsport. Yes they are not cheap but an inaccurate diagnosis will be a very expensive mistake !
The flat bed will cost you more than the diagnosis. Savings can be made elsewhere perhaps but a cheaper diagnosis ..........
Ask local PCA for recommendations ?
There are M96 repair places like 9XX Motors in LB and his buddy UFO in GG or Auto Strasse in CM - but first you need a diagnosis. Be prepared to be given a list of possibilities with probability and cost for each.
Once a mechanic starts tearing into the engine you are trapped.

Thanks guys, do you hear the same sound in this video taken a few days prior?

Nope ! Flatbed before you do more damage.

You need Jake's golden ears.

No just about 45 seconds, 5 to 10 of which is oil level read time.