I lived with this problem for couple of weeks, it turn out to be leaking transmission, the transmission oil will dripp over the exhaust pipe and will produce white smoke and you can smell the burned smell in the cabin. And the funny thing was the Oil will not drip when car is in idle, it would drip and smoke after I drove couple of miles. After installing and reinstalling Trns. pan numorous time, changing the pan gaskit, I narrow it down to the metal seal under the neutral safty switch.
You might be having similar problem, check underneath the Tranny Pan for any leaks.
I sure hope it will help, keep us posted.

Thanks

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87 420 SEL
Looking for a nice mid 80's MB diesel.
87 BMW 528e (Sold)
99 TOYOTA 4Runner
1989 Honda Accord (Sold)
1988 Honda Accord (Total)