Toyota 25870-66010 Valve Assy, EGR Vacuum Modulator

To adjust NOX emissions, some of the exhaust gases are directed into the intake manifold through the EGA valve decreasing the maximum combustion temperature with EGA valve being the main unit of the system. It coexists with such devices as EGA vacuum modulator, Bi-metal Vacuum Switching Valve, Vacuum Switching Valve as well as Vacuum Transmitting Valve, however not all of these are incorporated in every product models. When the engine temperature is low, the VSV or BVSV and the EGA valves are closed which consequently block the exhaust gas recirculation. It is stated that in proportion to the increase in the engine temperature, the VSV or BVSV opens whereas when the throttle valve is sufficiently opened to expose the EGA port and when the pressure in the EGA valve is low, it leads to pressure build up which closes the modulator and opens the EGA valve. This cycle goes on depending on the coolant temperature, the exhaust gas pressure, the fuel flow pressure and the position of the ignition switch. If the engine bogs down at idle, hesitates on acceleration, accelerates poorly, or gets poor fuel economy it could mean the EGA system is not turning off. Look at all vacuum connections for the proper connection and integrity and replace any cracks or damaged hose to the EGR valve. Also, clean the EGR vacuum modulator filter to determine if it is clogged or damaged, and if this is the case, clean it with compressed air. If the vacuum hose is disconnected from the EGR valve and a vacuum pump connected to it, then the application of vacuum should make the engine to vibrate or stall, normally this is the time to replace the EGR valve. For replacement, the vacuum hose should be disconnected and the valve removed by the removal of the retaining bolts, after this step a new valve should be inserted and secured through the bolts, then hose vacuum should be connected once again.

The EGR valve is typically located on the intake manifold.