White smoke is comming out of the Exhaust Pipe when i start my 911 Porsche Engine. It stays for abaut 3-4 min. and it is like white Fog

What is year--make--model?
Are you losing coolant? The white smoke may be coolant in the combustion cylinder, possibly caused by a head gasket problem. If head gasket problem, fix that first.

With idle issues, clean/check anything that has to do with idle air system. Any applicable trouble codes?

http://www.carsdirect.com/car-repair/causes-of-white-exhaust-smoke


Causes of White Exhaust Smoke

the white smoke occurrence is due to unique Vehicle usageconditions like slow speed & Short trips drivingthe catalytic convertor is not able reach its optimum reactiontemperature. As a result, the Hydrocarbon accumulates in the Catalytic Converter.After sometime, once the saturation limit is attained, the accumulated Hydrocarbon
starts burning inside the Catalytic Converter. During this Chemical Reaction,Momentarily the white smoke is seen in the exhaust and is normal

if the oil is leaking onto the exhaust pipe this will cause smoke as the exhaust pipe gets very hot & burns the oil, you will need to find out just where the oil is leaking from & repair the leak by replacing the gasket or whatever is causing the leak.....hope this helps......cheers.

Check to see if there is white foam on the dipstick when you check the oil. If there is, then you have a cracked head or a broken head gasket. Antifreeze must be getting in the cylinders.

The oil was overfilled this could cause a large amount of oil to enter the exaust and possibly the intake depending on crank case ventilation conditions. If you are positive engine oil levels are adjusted perfectly(warm engine check level running for dry sump oil level ect.). Time is needed to burn off oil residue in exhaust system and intake. Warm up engine low rpm no load, drive vehicle slow with little boost over 5 mins slowly raise rpms for another 5 mins keep driving smoke will burn off while making other drivers mad. sorry just smile and wave.
The engine oil on this vehicle should only be changed by an experinced tech.

could be water vapor from a bad head gasket or emissions sytem malfunction.

that oil leak or another is dripping on to the exhaust manifold or exhaust pipe ,that is where it is coming from,,

This is probably just condensation in the exhaust, if you are not loosing coolant that would be me guess.

you have a blown head gasket you need to get it to a shop as soon as you can