I took the wife's Boxster to work on Friday and gave it a little work out on the way. TBH it was one short sprint on the journey of only about 1/4m (pointlessley racing a sport bike
) and apart form that nothing that I would say was anything particularly strenuous on the journey. No max rev stuff or hard acceleration.
The following day I started the car and there was a was big cloud of white smoke on start up but the engine ran fine and I can't get it to do it again. The car only has 50k on the clock and has been driven gently all its life.
I'm hoping its a one off but I've hoped for those before.....thoughts?
In spite of the white color I suspect the cloud of smoke was oil smoke.
If if was water vapor the cloud dissipates very quickly even if there is no wind/breeze.
Oil smoke hangs together as the cloud drifts downwind.
Given the circumstances of the car's usage before you parked it up, I'm guessing the smoke was oil smoke and this is normal.
Even new Porsches emit oil smoke upon startup and the techs tell me that all they do is observe that the smoking is short lived, observe if the engine is otherwise acting up, running abnormally rough, or if the CEL is flashing or even solid on, and absent any signs of distress pay the smoking no mind.
The hard running you engaged in I strongly suspect puts a lot of oil in the intake system, make that on the intake system's inner walls.
This oil comes from an AOS that is lousy at separating the oil vapor from the fumes it passes to the intake.
Upon engine shut off this oil on the intake manifold walls drains down and gathers in one or two cylinders and upon the next engine start clouds of oil smoke billow forth.
(Techs tell me that almost every engine that comes in that if they have an opportunity to inspect the intake manifold find the walls damp/even wet with oil.)
My usual advice to cut down on the smoking chances is to use a proper oil, make sure the oil is not too old, that is has too many miles on it from which is gets thinned out by water and unburned gasoline, and the engine is not overfilled with oil.
If you can before you shut off the engine give it a moment of idle time. However, if you have been running the engine particularly hard this may not be enough to see all the oil deposited on the intake walls drawn into the engine and burned.
A really hard run should see the car driven a few minutes at moderate speeds and engine loads to shed the heat load that hard running creates -- which is important enough to mention it first -- and to give any oil time to pass from the intake to the engine and be burned.
Even if you do the above -- based on my experience doing the above -- the engine will smoke upon occasion. The culprit? The AOS just sucks in removing oil vapor from the crankcase fumes.