on starting up there's sometimes a large white cloud of smoke ,this comes and goes and it can be weeks in between. of course everytime i book it in to the dealers it goes and no fault can be found.
you have high mileage? that seems like build up on the valves or else an oil leak on the valve seals... you must be using cheap gas and its leaving deposits. Try using a product called "lucas fuel treatment" it goes in the gas tank, and also fill the tank with premium fuel EVERYTIME. I personally like shell's premium I have 3 BMWs and i work for BMW, shell has the highest quality of gas.
If you're talking about the white cloud of smoke coming from the hood, it's a possible oil leak from an old engine gasket. I replaced mine ($60) when I noticed white smoke from the hood at traffic stops and an oil burning smell coming from the vents and she's been running better than ever. Hope that's your solution!
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