It causes oil to leak into the intake.
The below information and this link should help.
NUMBER: 09-05-00 GROUP: Engine DATE: Feb.25, 2000
MODELS:
1994 - 1999 Ram Van 1994 - 1999 Dakota 1994 - 1999 Ram Truck 1998 - 1999 Durango 1994 - 1998 Grand Cherokee 1996 - 1998 Grand CherokeeThis bulletin supersedes technical service bulletin 09-06-99, dated September 10, 1999 which should be removed from your files. This is a complete revision and no asterisks have been used to highlight revisions.
SUBJECT: Spark Knock And Engine Oil Consumption Due To Intake Manifold Pan Gasket Oil Leak
OVER VIEW: This bulletin involves the replacement of the engine intake manifold plenum pan gasket.
NOTE: This bulletin applies to vehicle equipped with a 3.9 liter, 5.2 liter or 5.9 liter gasoline engine.
SYMPTOM/CONDITION: An engine intake manifold plenum pan gasket oil leak may occur on some V-6 and V-8 style engines. The oil leak is internal to the engine so no external oil leakage will be present. Two symptoms of this oil leak condition may be present. The vehicle operator may experience an engine spark knock during acceleration and/or an increase in the amount of engine oil consumed by the engine.