pvanosta

My CTT is 2008, with 65,000 miles on the clock.
Recent maintenance included new spark plugs and new coils after a 'misfire cylinder 8' error a couple of months back.

Now a new issue develops. The best I can explain it is this: when I 'engine brake' (lift my foot off the accelerator while in gear, such as when going down a hill) and at the bottom of the hill I get back on the gas, there is a brief hesitation followed by a huge bellow of blue smoke from the exhausts. Every single time. It's as if the 'under-pressure' during the engine braking forces/sucks oil into the combustion process (I'm no mechanic, so forgive me if this sounds ignorant).

This results is an oil consumption of 2 quarts per 500 miles when driving in hilly country.

There are no error codes.

Any idea what I am looking at? Is this something that could be caused by a defective/leaky air-oil separator? Something else?

Any suggestions are welcome.

ScootCherHienie

That much oil use is pretty serious. I'm not sure driving it is a good idea until the problem is fixed. Worn valve guides/seals can leak that much oil, but it would be unusual for oil consumption to change quickly... generally oil use would increase slowly over time. Head gasket could be leaking on one side (check cooling system for evidence of oil and check oil for presence of coolant in the oil. You could have a head gasket leak that allows oil into a cylinder. Examine the spark plugs to see if there is evidence of oil contamination on any of them. If the spark plugs all look good/normal (not black/sooty and possibly wet looking), the oil is coming out somewhere else. Also examine the sides and bottom of the engine as best you can to see if there's evidence of oil leaking outside the engine anywhere. But blue smoke in the exhaust after getting on the gas certainly SEEMS like the oil is getting into the cylinder severely under higher vacuum situations. My guess is that you are going to find 1 or more spark plugs that look pretty nasty. If so, any good shop should be able to diagnose the problem. If you are lucky and there's just 1 black/sooty/wet spark plug, the number of causes will be pretty limited and should be fixable easily enough.

Petza914

Smoke on acceleration is usually cylinder or ring wear whereas smoke while off the gas going down a hill is usually a valve or head issue. In Porsches, it could also be a bad AOS (Air Oil Separator), which should be tested with a manometer.

If you have someone follow you they can tell you whether you're getting smoke when off the gas going down hills or only on acceleration. A compression test might not be a bad idea if you're pulling the plugs for inspection anyway. That much oil consumption is pretty major.

pvanosta

There are no leaks anywhere. The engine is clean on all sides (as clean as an engine can be).

The smoke only occurs after a downhill / engine brake and even then only when I re-accelerate. It's at that precise transition from engine brake to boost/aceleration that there is just the briefest judder and a cloud of smoke.
The rest of the time it does not smoke visibly.

I am hoping it's only the AOS. Would a dead or dying turbo behave like this? If it is Cylinder or Ring wear, what am I looking at in terms of repair (I have no idea what or where a ring might be btw).

Petza914

If you've never followed the car when it's being driven by someone else, I don't think you can say definitively that there isn't some smoke at other times. There can be smoke that you can't see in your rear view mirror from the driver's seat that's less than the big plume you describe. The other thing to check is how much oil has accumulated in the Driver's side intercooler. The crankcase ventilation system runs oil vapor back to the intake on this side for emissions purposes and the intercooler condenses that vapor back into oil. If there's a lot of oil accumulated in that intercooler, the vacuum of the downhill throttle off situation could suck it into the intake and then the transition back onto the gas blows it out the exhaust. The intercooler should be disconnected and drained every 2nd or 3rd oil change. Those who don't understand the venting system when they see oil accumulated in that intercooler assume it's turbo blowby from a bad turbo, but the turbos themselves on these very rarely fail and it's a misdiagnosis.

What's a ring - a compression ring or rings are, thin, hard carbon steel rings that reside in the grooves in the top of the pistons and are what seal the combustion chamber during piston travel for the 4 strokes a motor goes through - intake, compression, combustion, and exhaust. If the rings are damaged, worn, installed incorrectly with the grooves aligned or anything else )scored cylinders) that prevent a good seal and allow for the fuel or fuel/air mixture, or exhaust to slip past the rings, it burns the oil on the cylinder walls used to protect them and that oil coming out during the exhaust stroke iw what makes the blue smoke. A compression test of each cylinder will tell you whether you have a problem there and that problem could either be related to the block, pistons, or rings, or to the heads with an intake or exhaust valve not sealing correctly. Low compression in Porsche engines almost always results in misfires though and then a CEL. If you don't have a CEL where you can pull specific P-codes to see what those are, then it's probably the AOS or accumulated oil in the intercooler.

pvanosta

Pete, thank you very much for that thorough explanation. No CEL, but I will take all of this to my Indy and we'll take it from there. Thanks again.

Dilberto

PCV check valve has developed "scalloped" diaphragm edges, due to either excessive crankcase pressure, blowby or simply a hot glob of sludged oil passed through it. Shoot B12 Chemtool inside all 3 ports and when dry, blow inside each orifice opposite of oil vapor flow to get the edges seated correctly again. If the orange diaphragm inside is damaged - buy a new check valve...

TomF

I hate to say this, but that kind of consumption indicates something very serious is going on and you shouldn't be driving it at all. Have your indy pull your plugs and see if one or more are fouled. The valves very rarely have issues and a failed AOS will throw codes pretty quickly. If you have one or more fouled plugs, do a compression test. While this is in no way definitive, a fouled plug and lower, ie. 15-20% less (or more) on a cylinder can be strong indication of cylinder scoring. Then it's time to dig further.

Keep us posted.

Best,
TomF

nodoors

That sounds like way too much oil to me to be an AOS or PCV check valve, but I sure hope it is one or both for your sake! It takes about 5 minutes to see if you have a tear in the AOS membrane and to remove and check the check valve for operation and excessive oil in it. IF you don't find either to be faulty, and even if you do pull all the plugs again, number them and take pics, and do a compression test as Tom F says.

Dilberto

Cayenne Turbo correct oil fill on dipstick, is exactly at the center "dot" between MIN and MAX. Thermal expansion will raise the level another 1/2 quart to MAX when at operating temperature. Anything over that may blow into the intake runners and pool there, until burned.

user 83838290

Drain your driver's side IC first of all

pvanosta

Well, the Air-Oil separator has been replaced and the issue persists...
Mechanic to suggest next step plan. Does not expect any cylinder or engine damage (no CEL and the car runs fine) but will need to take off the engine cover as part of the deeper diagnostic...

Ideas anyone?

user 83838290

Did he drain the IC and pipe?

Petza914

i tried that before my FL trip last week on my 09 Turbo S and after fully warmed, parked, and checked 3 min and 10 min later, it was still only 2/3 of the way between the marks. Added about 1/6 qty and then ir was just below the full line when fully warmed and rechecked.

The OPs oil has to be going somewhere and has must be burning so its either turbo blowby, scoring, or a head/valve issue. Compression and leak down tests should probably be the next steps.

prosled8

I see that the denial still runs deep around here. My bet is on scored cylinders. Your previously fouled #8 plug was the warning, it can go downhill quickly once the scoring starts. Cayenne turbos almost never have valve issues, rarely have turbo issues and you addressed the common easy fixes already. You need to find a new mechanic if he still doesn't think it is serious. With that much consumption just scope #8 from the top, I bet it is scored, and I bet it isn't the only one. Guys, this is how most of these engines will fail over time. Witness the increasing number of cars going down. Sucks but, I bet your CTT needs a new/rebuilt motor.