Throttle Modulator Diaphragm Check

Disconnect manifold vacuum hose from solenoid valve at diaphragm unit. Plug end of hose. Using an external vacuum source, apply 19 in. Hg of vacuum to the diaphragm. Check for throttle arm movement.
If throttle does not move, check linkage and repair or replace as necessary. If vacuum leakage from 19 in. Hg to 12 in. Hg of vacuum takes less than 2 seconds, replace diaphragm unit.
Check position of adjusting screw on diaphragm housing. Ensure adjusting screw does not interfere with mechanically lock-out movement of throttle linkage.
Release external vacuum from diaphragm. Diaphragm should retract to original position within 5 seconds. If not, replace throttle modulator. Remove plug from vacuum hose and reinstall on diaphragm.