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In Reply to: Smoking bmw posted by rich medina on November 08, 2001 at 16:15:22:
Valve seals at the top of the valve guides. They wear out. When the car sits for a while, oil that has gathered on the valve train, seeps through these worn seals and runs down the valve stem in the valve guide. There, it pools on the heads of the closed valves, or into the cylinders of open valves. When you start the car, the oil burns off the valves and out of the cylinders, resulting in a light blue-grey smoke from the tailpipe for a few second, or as long as a minute.
The other time you will see smoke due to this condition is on heavy deceleration, like shifting down excessively, or rolling down a long hill using engine compression to slow. This compression sucks oil down the guides and into the cylinders.
This condition is typically only an inconvenience, resulting in increased oil consumption, usually only on startup, and possible plug fouling, which usually also burns off. The fix is new seals, but they will wear out again. The seals were unreliable until mid 80's. You will hear differing opinions on this however. Also, almost impossible to replace these seals with head on car, so most wait until it's valve job time.
When you compression test an engine with this problem, you will get good compression readings, since this is not a problem inside the combustion chamber. If you get bad compression readings you have other problems,... ie. rings, burnt, or damaged valves.
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