Started car with white puff of smoke

After sitting for almost two weeks, I started the car and a white puff of smoke came out of the exhaust pipes. I also release the oil filler cap easily. I hope this is not the first sign of AOS.

Something not quite right I suspect. Maybe there are more knowledgeable posters reading who may chip in here to assist you. 2 weeks is an awful long time for a Porsche to be standing.

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A puff warrants monitoring. In my opinion, acting on this incredibly common issue would be premature.

That's not enough information to go on. A single white puff of smoke? Was it billowing smoke out the exhaust for several minutes or did it just blow it out when you started it? Was it coming out of both exhaust pipes? Parked inside or outside? Last drive - did the car have a nice run, get fully warmed up, or did you do a short run? Visually check all engine fluids, i.e., coolant, oil with the dipstick. How many miles on your car? An air oil separator going bad is not the end of the world, just a pain to replace. And it will have to be replaced anywhere from 60,000 miles on up. Also, I sit a traffic lights in the morning and watch water just pour out the exhaust pipes of some cars...a factor of combustion, ambient temperatures, warming up the cats and exhaust system, high humidity and condensation. Have you ever watched the cars in cold weather...they all exhaust water, steam as a by-product of combustion. Monitor, check all fluids, give it a good run of 20-30 miles, and report back.

If I had a dollar, I'd bet that OP had a single good-sized puff of white smoke, and it probably hasn't done it before (or often), and it hasn't done it since.

Yep - it's happened to me where my car blew white smoke twice and that was that. Had been sitting a couple of days after a short trip.

Quotes source post: 11540550

Based on my experience, the first sign of a bad AOS is when the salesman hands you the keys to the car. The only question then is when, not if the AOS will go bad. The puff of smoke is probably nothing to worry about. The techs tell me they see this all the time, even from new cars. The cars get started but not driven hardly at all as they are shuffled around on the showroom floor and the car lot. As long as the CEL remains off, and there is no other untoward behavior from the engine, and the smoking is short lived, there is nothing to worry about. The smoking has nothing to do with how long the car sat. It has more to do with the engine before the engine was shut off. While some believe the oil seeps past the rings when the engine is shut off this is not the case. The combustion chamber, piston crown are hot. Oil does not flow towards heat but away from it. (Test this: Put a cast iron skillet on the stove, put some cooking oil in the pan and turn on the heat. As the pan heats up the cooking oil will tend to migrate away from the hotter areas, the layer of oil on the pan bottom will become uneven as a result.) Where the oil comes from is I believe the good old, err make that the bad old, AOS. The AOS is pretty much junk. It is junk in that it is not very good at removing oil vapor from the crankcase fumes. Thus when this vapor makes a sharp turn at the intake manifold some of the oil in the oil vapor can't make the sharp turn and impacts the wall of the intake manifold. As long as the engine is running this oil gets ingested by the engine and you do not even know it. (I suspect that in some cases "excessive" oil consumption results from an AOS that is particularly lousy at oil vapor removal.) When you do know it is if you shut off the engine before this oil gets into the engine. Then as the intake warms up from heat soak the oil flows down and into a combustion chamber if the intake valves are open. If they are closed the oil puddles on top of the intake valves. Upon the next engine start the oil gets burned, incompletely burned because the engine is cold as are the converters, and what you see is a puff of smoke. The things you can do to reduce the smoking is to let the engine idle a moment before shutting if off. The harder you were pushing the engine the longer you should let it idle. This won't work all the time but it does help reduce the frequency of the smoking and its severity. Ideally you should drive the car long enough the engine is fully up to temperature, but this can't always be arranged. Keep the oil level up but do *not* overfill the engine with oil. Use a proper oil. An improper oil may foam more or have other characteristics that make it more prone to vaporizing in the crankcase. Do not run the oil too long. As the engine runs the oil accumulates unburned fuel and water. These work to make the oil more fluid, and tend to cause it to foam more. More foam produces more oil vapor in the crankcase which means the AOS gets the opportunity to fail to remove even more oil vapor from the crankcase fumes before they are routed to the intake manifold.

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I was going to share all this knowledge too, but Macster beat me to it :-)