This Preliminary Information communication provides information to the technician about vehicles that have a Service Engine Soon Malfunction Indicator Lamp on a rough running engine, and/or oil consumption. Technician will find Diagnostic Trouble Code P0300 set. Technician will apply regulated air pressure through the PCV pipe and spray soapy water where the PCV baffle and valve cover meet with soapy water to inspect for possible signs of a leak. Technician will replace the value cover if a leak is present.