One morning not so long ago I started my 997.2 3.8l and there was noticeable cloud of white smoke. Not like an old Wankel but big enough to think 'WTF!' on a car with 20k miles.

It's a daily driver [now] and have cold started it maybe a hundred times since with no such issue. I'm wondering if anyone else has experience with this. Things to watch for, worry about...

Thanks for any input,

Z.S.

 

Air/oil separator?

Mine went bad on my Cayman R at about 20k miles. Started with cloud of white smoke. Smelled sort of like oil, and at first it was just a cold start but then it would smoke as I drove down the street.

 

I'll mention that at the next service. I got it CPO.

Thanks.

 

The design of the flat 6 motor with horizontally opposed cylinders can allow a little oil to collect in the cylinders, especially if driven hard time before this cold start that had the smoke come out. Could also be the start of a failing AOS - if so, you'll know about that soon enough, as it will smoke more and then when it totally fails, smoke will come billowing out the exhausts and it will be very difficult to remove the oil fill cap with the engine running. Might also start hearing what sounds like a squeak or a whistle as air slips past the separator diaphram.

 

Just to expand on this, it becomes difficult to remove the oil cap with the engine running because a failed AOS will create a large vacuum in the crankcase. This is only one symptom but it doesn't always show on a failing AOS, just a failed one.

 

Probably just normal. The Porsche techs tell me they see this often with new or used vehicles on the lot. The SOP is to just observe the behavior of the engine. If the smoking stops almost as soon as it starts, if the engine doesn't manifest any untoward behavior, if the CEL remains dark, it is just normal.

The techs tell me invariably when they are working on an engine and open up the intake they find the intake walls oily. The source of the oil is the hose that comes from the AOS. The AOS is just not able to remove all oil vapor from the crankcase fumes and as these fumes reach the intake and have to make a sharp turn the heavier oil vapor particles impact the intake wall opposite where the hose connects. If this happens with the engine running the oil makes its way down into the engine and burns and one is the wiser.

If the engine is shut off the intake heats up and the oil runs down and if the intake valves are open on into the cylinder. If the valves are closed the oil collects on the valves.

If the engine is started cold this oil doesn't burn completely and smoking is the result.

My experience over the years is both of my cars (2002 Boxster with over 312K miles and a 2003 Turbo with over 155K miles) will experience a hundred or more starts with no smoking between starts when there is smoking.

My usage seldom has a cold engine started and then the car put away again without the engine having been run long enough to get fully up to temperature. It is this type of usage -- short trips -- that seems to encourage cold start smoking.

Also, I have over the miles observed that as either engine gets close to being due for its 5K mile oil/filter service the engine is more likely to smoke upon cold start even though the engine was fully up to temperature when I shut it down.

About all you can do is what the techs do when the engine smokes. I covered this above and won't repeat it again here.

Furthermore, my advice is if you can avoid short trips. Longer trips get the engine up to temperature which helps reduce the possibility the engine will smoke at its next cold start but it also helps remove water from the oil and helps keep the battery topped up. The engine needs to run some time -- 10 or 15 minutes or longer -- in order for the battery to be topped up.

Avoid overfilling the engine with oil.

And last but not least don't run the oil too long. As the oil accumulates miles it gets contaminated with unburned fuel and water and other combustion byproducts. These all work to increase the tendency of the oil to foam and create more oil vapor which overloads an already overloaded AOS.

 

Same happened to my old 996 a few times, and as Petza914 say I believe it's a little oil being burnt. Now if this happens every single time you start the car I'd take it to the garage for a check up.

PS. I also thought it was the AOS the first time it happened and took it to Porsche who couldn't find anything.

 

Normal occurrence for me if I start the car while cold, move it in the garage to position for working on it and then shut down after about 30 seconds of running. Usually next start will billow out smoke. As explained above the phenomenon is part the horizontal design of the engine. A failed (or failing AOS) will be very evident.

 

Thanks everybody. I think I'll bide my time and observe...mention it next time I go for service. Unfortunately I already had the 20k service done.

I do occasionally give my 911 an Italian tune up. That could be the culprit, leaving a bit of oil.

Cheers,

Z.S.

 

I have noticed the same thing with mine. I think it has to do with the cold start mechanism idling the car at a higher rpm for a minute. Maybe extra fuel?.. If I am simply moving the car to wash or work on it, I will let it idle until the rpm drops from the cold start higher rpm. Never happened since.

 

I have a hypothesis that even though my dealer is doing the oil changes by the book using the PIWIS for that final measure, the PIWIS full level in my car will generate a crankcase oil fueled smokey start up at the next start up after a higher than normal (Sport mode) run. My oil changes are in Spring and I was seeing this over the summer maybe 2 - 3 times. After the summer into fall, no smokey starts. I have never had to add oil and usually when it is time for an oil change it is down one marker.

This has been fairly consistent since "new" to me (5 years ago with less than 6000 miles currently at 32,000 miles).

This oil changed I asked them to fill one marker low. They complied and I have not had a smokey startup since the Spring oil change. Time will tell.

 

Mine has smoked a few times at start-up and I'm pushing 70K with oil changes every 5K. The oil is never higher than half way up/down the oil test;

1/ once when it was cold and after I moved it a car length and then started it again after a few minutes. It was as @jhbrennan mentioned but it only lasted a <5 seconds. I did shut it off, briefly inspected the engine and re-started it and all was well.

2/ two times when it was relatively warm and the car was parked on a side-to-side angle (one bank higher/lower than the other). Just a puff of white smoke out of the tail pipe on the lowest side of the vehicle (as per Wayne Smith...FWIW, I've never seen Wayne's 997 do that...and he has confirmed that his flat-6 is a smoke free engine!)

 

To be accurate, if I park sideways on a slope, sometimes oil left on the cylinder wall will pass the rings as they cool and I end up with a brief smoking start. We don't have V6 motors after all!!!

 

White smoke on start-up can happen if u parked the 911 on an incline