Vacuum Control Valve Adjustment

With engine at normal operating temperature and using a stop watch or watch with sweep second hand, raise engine speed to 3000 RPM (without load) and then immediately release throttle. It should take 3-5 seconds for speed to drop from 3000 RPM to 800 RPM. If time required for drop is less than three seconds, turn adjustment screw on control valve clockwise. If time is more than five seconds, turn adjustment screw counterclockwise.

Fig 1: Subaru 1300 & 1400 Timing Marks

Courtesy of SUBARU OF AMERICA, INC.