Help: 996 Smokes on cold start, AOS failure?(Videos)

Hi guys, I own a 2004 996 C4S Cabriolet for 1 month, has 111.000 kms (69.000 miles) on the clock. I am the 2nd owner (1st owner had the car for 8 years), full OPC history at Lisbon's OPC, car in great condition and runs great. Before payment, took the car to Lisbon's OPC to do a PPI and ended up getting a new RMS + IMS seal (both were leaking) and new clutch (at previous owner's expense). They told me the car is in great shape and in fact it drives very well. As the car was already there, I requested them to do the major service including new spark plugs, new belt and brake fluid replacement. All this at 68.500 miles. As I am reading a lot of horror histories about 996 ownership, I am getting a bit paranoid... The car is only driven at weekends. This past week it rained a lot in my area and had cold weather most of the time. Yesterday I found out that the outside of the left intake piping/hose was very dirty, what made me think of oil inside the intake hose seeping through the brackets due to potential AOS problems. Please look at the photo: So I went on the web and started reading everything I could about AOS failure. When the engine is started for the first time after a cold night, it does smoke for almost 1 minute and some water is expelled through the exhaust. Today I started it for the first time at 16h30 and filmed it. Please check the video (105 secs, close to the end of the video there's a close up of both exhaust tips in which it's easy to see the water inside them): You Tube Always thought this was due to water condensation inside the exhaust during the night but after reading all the AOS failure posts, decided to do the oil cap removal test (engine was still cold, been running for just 3 mins) as seen on the following video (35 secs): You Tube Engine had a hard time keeping idle and exhaust smoked a bit more. As engine was still cold at the previous video, decided to do a short drive (10 min) to get the engine to "regular" working temp (80�C / 176�F) and did the oil cap removal test again, as seen on the following video (35 secs): You Tube It went a lot better, the engine didn't have such a hard time keeping the idle steady and no smoke from the tail pipes. No water on the tail pipes also. On both oil cap removal tests while engine running, I didn't have any problem removing the oil cap, didn't really feel any significant suction from the oil feed pipe. Never got a CEL light to this day. I am thinking that if my car had an AOS problem, the OPC probably would have found it during the PPI or the following major service that was done. They never mentioned anything to me. On the other hand, I know how brand's dealerships after-sales departments work... I am myself another brand's owned dealer manager... As my 996 didn't show any error code/CEL on the diagnosis, they probably didn't go fault hunting... Forum, after all this info/videos should I stop driving the car immediately and take it back to the OPC to find out why the intake pipes are dirty underneath? Do you guys think my AOS is about to fail? Any help will be appreciated! Regards, CS PS - Sorry for the huge post!

From what you posted I do not get the sense the AOS is bad. The one minute "smoking" you mention reads more like water vapor than smoke. Smoke hangs together as it drifts away while water vapor dissipates. That you first started the engine on a cold night reinforces water vapor as being an explanation. Unless of course you are sure the smoke was indeed smoke and not water vapor. The water vapor comes not from residual water in the exhaust system but is a combustion byproduct. It is very similar to contrails jets leave, though at their altitude the water vapor freezes to ice. Oh, I forgot about the videos. I watched the 1st one a while and the smoke looks to be water vapor. Note there was not any sign of smoke upon engine start. Typically a bad AOS will cause a smoke cloud from the very beginning of engine start. Also, I observed the smoke dissipated within inches of leaving the exhaust pipe. The engine's reaction to the removal of the oil filler tube cap is what I would have expected. Removing this cap creates a big intake air leak. The engine controller DME can adapt but it takes a moment. In the meantime the engine will not run as smooth as it was running before. That the engine was cold compounds the effects of the cap removal since the cold engine needs a rich mixture at this temp anyway and then to have this turn lean... well what you observed is to me to be expected. Absent any hunting idle, hesitation off idle when the engine is warm, no CEL and no other engine symptoms I'd have to guess the engine and its AOS is just fine. The bit of oil leak sign could be a number of things. Best to have that looked at to know what someone at the car believes it to be.

That looks like water vapor to me, no blue tint to the smoke at all. My 4s has vapor coming out of it when first cold started as well. Looks totally normal to me. Do you feel vacuum when you put your hand over the oil filler tube and the car is running? As Macster said, you can hear the engine dialing in the mixture after you took off the cap, which means the o2 sensors are seeing more oxygen due vacuum leak you created.

Cs,its hard to see because you dont show it long enough but that looks like a lot of moisture in your oil fill tube and cap. Could you post a still photo of oil fill tube and cap? How does the oil look?

Quotes source post: 10076864

I have tried that also and I really couldn't feel any vacuum. I am glad common opinion is that my AOS is ok. Any ideas on what may be causing the oily mess around the intake pipe? Thanks.

Quotes source post: 10077030

These pics were taken 1 month ago when I bought the car, I cleaned the oil cap and the oil filler tube at that time. Today both the oil cap and oil filler tube are a bit less messy.

That is vapor to my eyes. The oily residue on the throttle body (or left of) is common. I have cleaned that off on my car with a bio-degradable cleaner and a pressure washer. Put a plastic bag over the air intake and use masking tape to keep it in place. Spray the entire engine bay and let it sit for a few minutes. Power wash it clean and all is nice and shiney. The creamy butter in your fill tube is common too....usually seen in cooler temps. It is condensation in the oil. Cars that are driven burn that condensation up.

Can u take a drive and make sure. That looks like a lot of moisture in the tube. Didnt u say they just changed the oil? My car is older than yours and has lower miles. Never looks like that. Like Pete said, I think I would clean the whole engine spotless first, then see what happens.

Forgive me if Im wrong, but this is what it should look like to be "normal". This has not been cleaned, car is not a DD, and temps have been all over the place from 30's to high 70's within the last week.

That is just one normal. There are some cars that will develop a bit of goo around the cap. Different climates, different driving styles, length of time the oil has been in service are all variables.

You really need to take that car for some long drives, it will clear up the gunk. My car does exactly what yours does on the video. Normal!

The last time the car was run, was it only run for a very short time (like one or two minutes)? If my car has been sitting for a couple days and I start it for a very short time (say, to just move it to another spot in the driveway). The next time I start it after that it will give a puff of smoke when I first start it (actual smoke, not condensation). I recall reading somewhere on here that is very common and has something to do with the design of the engine and where/how the oil accumulates when you shut the car down and cold oil doesn't drain from those places as well as hot oil or something like that?

The oily residue around the intake clamps is very normal for that many miles. AOS takes the majority of the oil out, but many vapors are sucked in to be combusted (it's purpose), and some will always seep through. Whenever there is any oil leak anywhere, it seems like it always leaves a slight film that the dirt clings to over time. Wipes off easy. Not liking the goo in the filler pipe. Keep cleaning it out. Needs some long runs on it, like others said.

Hi forum, The engine was not ran for a week, on past Saturday I ran for 3/4 minutes to do this tests but at that time I didn't have the camera with me... So on Sunday I repeated the process and filmed it. So yes, on the day I did the filming, car had only run on the previous day for a very short time. Previous owner of the car drove it everyday. Then he trade in this car for a new Panamera at Lisbon's OPC on mid September. Car was parked on showroom for at least 6 weeks before I bought it. Since then, car spent a week on the OPC to replace RMS/clutch/IMS flange/seal (not the bearing) and full major service, then was driven 6/7 times at max, around 50 miles trip each time (open roads, not city traffic, 30 min trips). When I picked up the car, it already had the goo in the filler pipe, the OPC didn't clean it during the major service (even after I took the oil cap off and asked about it to their workshop technician). I didn't have the opportunity yet to do some "long-time/high-mileage" driving. I have however managed to take it to 160 mph on the highway one of this nights... I will clean it this weekend and try to do at least 150 miles and see if the goo shows up again. CS.

Some "goo" accumulation is normal for wet/cold weather driving. Anyone that has driven a VW Beetle year round in an area that gets cold has seen that build up on the oil filler pipe. I had a 1965 that I drove for 5 years. At some point every winter I would have to clean out about 1 cup full of that "goo" to be able to add oil. The pipe would be almost completely blocked with it. Never had to change the AOS or add antifreeze to it. That Goo is just like custard. Add 1 egg, 1 cup of sugar blend well. Pour it into a prebaked pie shell, top with coconut, bake for 30 minutes @ 350 and serve to your enemys. Then run Just out of curiosity is this your first car?

fpb111, it's my first Porsche. I am a sales manager for a Fiat Group owned dealer, so drive new cars everyday... for free. I also own a 1970 MGB roadster.

Look at the tail pipe on one of the other cars and see if it "smokes" on cold start in atmospheric conditions that concern you with the 996.