GM 96068663 Valve,EGR Vacuum Regulator Valve Check

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On earlier models, you can check the operation of the EGR valve by pushing on the diaphragm with moderate pressure. It should move smoothly within the housing.

The Exhaust Gas Recirculation (EGR) system is designed to reduce oxides of nitrogen in the engine exhaust. It recirculates a portion of the exhaust gas back into the intake manifold to be burned with the fuel/air mixture, reducing the temperature in the combustion chamber and lowering the oxides of nitrogen output. The EGR valve is vacuum operated and controlled by the modulator, which opens the valve wider under high-load conditions and reduces or closes it under light-load conditions. Fuel-injected vehicles in California also have a sub-EGR valve regulated by a PCM controlled Vacuum Switching Valve (VSV). The PCM, TWSV or VSV, and BVSV can override the vacuum modulator under certain conditions. To check the EGR system, start by checking the EGR valve diaphragm for movement when the engine is cool and then when it's warm. If the diaphragm doesn't move, apply vacuum to the valve using a hand-held vacuum pump. For fuel-injected California models, also check the sub-EGR diaphragm. Check all hoses associated with the EGR system for cracks or deterioration and replace if necessary. Check the EGR modulator by blowing air through it and checking if it holds vacuum. Check the BVSV by blowing air through it and checking if air comes out the bottom port when the engine is warm. Check the TWSV or VSV by blowing air through it and checking if air comes out the filter when energized. For 1999 and later models, check the EGR valve resistance using an ohmmeter and replace if incorrect. To replace components, remove the EGR valve by disconnecting the threaded fitting, vacuum hose, and mounting bolts. Clean the mating surface on the intake manifold and install the new valve. For the BVSV, remove the radiator cap, squeeze the upper radiator hose, and install the new valve. For the TWSV or VSV, disconnect the hoses and electrical connector, remove the screws, and install the new valve.