300DT Vacuum Leak Mystery

Calling all Merc detectives:: Every once in a while my engine won't shut off with the key, and the doors won't lock, so I know there is a vacuum leak. Funny thing is, most of the time everything works quickly
and perfectly. The problem happens about one time in twenty. Doesn't seem to have anything to do with air or engine temperature. So what would cause such an intermittent problem? Does it give a clue as to where the leak might be? What's the most efficient way to proceed when tracking down the leak?
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Try with the doors locked vs. unlocked.
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http://www.dieselbenz.info/dieseling_index.htm
snipped-for-privacy@hotmail.com wrote:

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thanks,
Darrell
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Good info there, Darrell, that includes T.G.'s tip. Thanks guys.
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