I had a Cadillac motor (390ci, 10.5:1 compression) that would do this on
occasion. I did some investigating, and learned that carbon build-up in the
cylinders can contribute to this. The carbon can have areas (usually peaks
of little mountains) which get super-heated while the engine is running, and
then act basically as a glow plug after you shut the engine off. There are
various snake oils out there which claim to clean combustion chambers, and
it probably wouldn't hurt anything to try one.
The other solution, which worked just great on the Caddy (with an auto) was
to just shut it off in drive, and then shift to park. The momentum of the
engine was sufficient to diesel in neutral (park), but not enough to keep
turning the torque converter. With a little tricky footwork, you can do
the same with a manual, slipping the clutch as you turn off the key... a
trick I've learned with my Jaguar that can also diesel at times.
Ryan.
55 2nd, Colorado USA.
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