pvanosta

@lupo.sk: if he didn't drain the IC and pipe, how long before that collected oil burns off?

@the rest of the participants:
Which of these issues would cause the blue smoke only under a vacuum (engine braking causing under-pressure, followed by re-acceleration) and NOT trigger a CEL:

- scored cylinder
- valve issue
- turbo issue (seems like this would cause smoking under heavy acceleration, which is not what I am experiencing)

user 83838290

Never. It stays there and does exactly what you describe.

Btw, My scored 08 CTT engine had 0 ISSUES. None. Zip. Nada. Went from hero to complete destruction in about 1 minute.

Petza914

OP, you need to follow your car while someone else is driving it, maybe while talking to them on a phone or 2-way radio so you really understand the circumstances under which it smokes, not just what you can see in the rearview mirror when you're driving.

Intercioler with accumulated oil could do this. As I posted earlier, valves under decell, pistons, rings, and cylinders under acceleration.

pvanosta

This is one of those moments where I love the internet and the information that is available in communities such as this one.
Took the car back to the indy today. I had printed out summary bullet points of things I wanted him to check, in ascending order of complexity / costliness.
1: check the intercooler and the intercooler piping for oil accumulation
2: check spark plugs for fouling (especially since they were all recently replaced 1000 miles ago)
3. If one of the plugs looks dirtier than the others, start looking at cylinder scoring, rings, etc. in that specific cylinder

I had the Air-oil separator and some intake valve replaced a week ago and he ignored the IC issue back then.
Today: he told me there was 'quite a bit of oil' in the IC and associated pipe. Cleaned it out. Tested the car. No more smoke
I will do more thorough testing over the next few days, but it looks promising.

I am posting this for 2 reasons:
1. to thank all who contributed in this troubleshooting
2. In case this is useful for other CTT users out there.

Petza914

Excellent news and nice to see I got one right back in post #5.

For the future, you could either install a drain valve (drill and tap in a petcock into the bottom of that intercooler) to prevent having to take it apart to drain the accumulated oil in the future, or could install a catch can setup (like a Mishimoto or similar) that will capture that oil before it gets to the intercooler and give you a way to drain it.

Wisconsin Joe

Thank you for posting the resolution on this. So many don't and we are left wondering.

Very, very, very glad to hear it wasn't cylinder scoring (somehow I have a funny feeling you are too).

J'sWorld

The PCV in the Cayenne leaves much to be desired, which is why the intake piping is full of oil. I know I have said it a million times but EVERY CAYENNE TURBO needs a catch can. Period. Based on my experience there are quite a few ill effects of sending this oil vapor back thru the engine to be burned. Everyone wants to spend all this coin on mods and overpriced products but fail to handle the basics first.

pvanosta

@Mr Haney: I did some baic reading on the catch can (Mishimoto?). Any more specific info and/or install instructions in a CTT would be very welcome, so I can include this job in my next trip to the indy.

Petza914

Here you go

https://www.6speedonline.com/forums/cayenne-turbo/354848-cayenne-957-catch-can-install.html

stefan063

Couldn't agree more...

stefan063

This was very interesting post... As I can see this is really important part for our Cayenne's ... So it catches oil from entering inter-cooler and cylinders!? Am I right? Also I got basic picture of product as a product I get that...But what Is benefit apart not being forced to disconnect inter-cooler piping to see if theres oil in them?! Just wondering

J'sWorld

The oil vapor lowers octane of the fuel considerably. The oil vapor collects, coats, and puddles- reducing efficiency of the intercoolers. The oil vapor passes through your intake and fouls plugs prematurely.. The oil vapor increases emissions. The oil vapor gets on the backs of the intake valves and seats which reduces airflow and heat transfer to the seat. The oil vapor gets burned into the ring lands and cokes up, reducing clearances, creating stiction, and clogging the lateral gas ports in the pistons behind the rings who's purpose is to push the rings against the cylinder walls creating a better seal on the thin and low tension metric rings used in the Cayenne v8. It's embarrasing when your Porsche smokes. Oil smoke stinks and leaves a lot more soot and carbon all around the tailpipes and rear of the vehicle.The oil vapor is detrimental to the health of your engine in general. Have I piqued your interest? There are several cans available that will get the job done for a reasonable price. The installation is simple. You can use 15/16 PCV hose. Not heater hose or anything else. Manufacturers do not install them because it can be another frequent point of maintainence. For those who dont know where the dipstick is this is a problem. For you , probably not so much.

pvanosta

The issue has returned with a vengeance after new spark plugs and new coils in April and a new Air-Oil Separator and some valve at te end of May (and a cleaning of the IC pipe).
After smoking again under deceleration/acceleration like before, car is now shaky and idling rough, not responding to throttle etc.
CEL showed up this morning.
Codes are p0308 and p0332 (Cylinder 8 misfiring and something with the valve lifter.

Going back the mechanic's on Monday. Any thoughts in the meantime?

J'sWorld

I wouldn't drop another dime on anything other than borescoping the cylinders starting with # 8. Everyone should keep in mind that the 4.8 has DFI, a much different variocam and oiling system, different pcv system and just a lot different in general.

DIYDanCars

My money is on scored cylinders. You seem to be having a constant problems with the number 8 cylinder. Most of the time when a Cayenne has a scored cylinder, it happens on number 8. The progression of events usually starts out with a ticking sound like a bad lifter, then the engine starts to eat oil like a mad man. Your high oil consumption has me leaning towards scored cylinders. Has your mechanic scoped cylinder 8 yet?