What Is a Vacuum Modulator Valve?

The vacuum modulator valve controls the amount and frequency of vacuum that is sent to the exhaust gas recirculation valve. The vacuum modulator valve is located inside a vehicle's transmission.

If the vacuum modulator valve is not replaced, the vehicle may experience engine stalling while idle, failure of an emission test, high levels of nitrous oxide emissions due to fluid being pulled into the engine, surging at highway speeds, an excessive or non-functioning EGR valve, hesitation while shifting gears if the car is automatic, and illumination of the check engine light. Failure to replace the valve may result in a blown engine.