As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING THE CLIMB AFTER TAKEOFF, THE CABIN PRESSURIZATION WAS DIFFICULT TO CONTROL & MAINTAIN. TROUBLE SHOT THE SYS & FOUND THAT THE LT ENG BLEED AIR CONTROL VLV WAS DEFECTIVE CAUSING THE PRESSURIZATION ISSUE. THE DEFECTIVE CONTROL VLV WAS REMOVED PN 1988-00-01, SN 0784A & AN OVERHAULED UNIT WAS INSTALLED. OPERATIONS CHECKED SATISFACTORY.