Toyota 25870-75030 Valve Assy, EGR Vacuum Modulator

For minimized emissions of NOx, some of the exhaust gases have been taken back into the engine through EGA valve to cool the combustion chamber temperatures. EGA valve is the central component of the system and it is accompanied by the devices that include EGA vacuum modulator, Vacuum Switching Valve (VSV), and the Vacuum Transmitting Valve (VTV), though the later two are not located in all models of the system. At low engine temperatures, the VSV and EGA valves are in the closed state thereby not allowing the process of exhaust gas recirculation. When engine temperatures increase, the VSV is opened and at an appropriate time when the throttle valve is opened to reveal the EGA port, pressure in EGA valve drops, and increased pressure shuts the modulator, while opening the EGA valve. Intake in turn follows pressure changes relating to exhaust gas recirculation depending in turn on coolant temperature, exhaust gas pressure and ignition switch position. If the engine itself roughs at idle, hesitates when being accelerated, accelerates poorly or has poor Mpg sticker, it is necessary to pay attention to the fact that the EGA system may not turn off. Before checking the EGA valve, ensure that all vacuum hoses are well connected and in correct condition, if any hose is cracked or damaged replace them. Also, ensure that the EGA vacuum modulator filter is not contaminated or damaged and if so, clean it with compressed air. To check EGA valve the vacuum hose should be disconnected and connected to a vacuum pump, applying vacuum should cause the engine to run roughly of stall; if this does not occur then the EGA valve requires replacement. For replacement, loosen the vacuum hose and then unscrew the four bolts associated with the valve, take out the old valve and then install a new one together with a new gasket then screw in the bolts and join the vacuum hoses.

A common issue that can arise in the emissions system is a stuck or defective EGR valve.

If the EGR valve diaphragm is immovable or difficult to move, it's time to replace the EGR valve with a new one.