Vacuum Modulator Valve
- Ensure atmospheric pressure tube is not restricted and vacuum hose is in good condition. With engine off, connect a hand vacuum pump to intake manifold fitting of vacuum modulator valve. See Fig 1
. Apply 19.7-23.6 in. Hg to valve.
- If valve does not hold vacuum, replace modulator valve assembly. If valve holds vacuum, remove valve assembly. Apply 19.7-23.6 in. Hg to intake manifold fitting again to ensure modulator valve moves.
- Valve should move in opposite direction when vacuum is released. Repeat these steps 2-3 times. Valve movement can be seen through oil passage on valve. If valve binds or moves sluggishly, replace assembly.
Courtesy of AMERICAN HONDA MOTOR CO., INC.