Common rail injector response characteristics depend on the control chamber pressure change rate, the outlet throttle diameter by manufacturing errors, or wear-induced deviations that affect the rate of pressure change in the control chamber, so the accuracy of the outlet throttle diameter directly affects the control valve response consistency. This paper presents a computational fluid dynamics (CFD) simulation of the effect of the deviation of the outlet throttle diameter on the average mass flow rate of the outlet throttle during the opening of the spherical valve in order to reduce this difference and ensure uniform injection characteristics. The results illustrate that with the increase in outlet throttle diameter deviation, the volume of gas phase in the control valve increases and the rate of pressure reduction in the control chamber accelerates, and the sensitivity coefficient of the average mass flow rate of the outlet throttle to the outlet throttle diameter deviation remains unchanged at 24.77. Cavitation occurs in the area of the outlet throttle when the spherical valve lift is 0.045 mm. The increase in rail pressure not only leads to an increase in the low-pressure area on the inner wall of the outlet throttle, an increase in the volume share of the gas phase, and an increase in the hydraulic impact on the sealing wall but also makes the average mass flow rate of the outlet throttle and the rate of change of the control chamber pressure during the opening of the spherical valve more sensitive to the deviation of the outlet throttle diameter.