Oldsmobile 17085929 Valve Assembly, Fuel Upper Cnst Control

The 2-barrel engines have EGA with a metering valve, vacuum line to the carburetor, and exhaust gas passages cast into the intake manifold. Called the EGA valve, this one is operated by the vacuum from the carburetor and opens and closes to enable the mixture of the exhaust gases with the fuel and air to provide a non-misfire or pinging at part throttle. This system reduces combustion temperature and hence decrease nitrogen oxides (NOx) emission, with the valve closed at idle and at full throttle. In many configurations, it is a thermal vacuum switch that regulates vacuum to the EGR valve in order to eliminate stalling and rough idle when the engine is cold. As the vehicle accelerates, the valve opens at specific vacuum with direct aim of admitting exhaust gases into the mixture. Some of the California engines have a provision that includes a dual diaphragm EGR valve to help in operation during non-constant vacuum conditions. Starting from models of the year 1977, manufacturers have employed back pressure EGR valves which are triggered by exhaust back pressure in order to control the EGR flow with respect to the load on the engine. The later models incorporate ported signal vacuum EGR valves and the particular systems employ pulse width modulation in order to control EGR under some circumstances. Measures that are taken to test for EGA issues include checking for EGA that is either too large or small, examining the vacuum hoses and testing the functionality of the EGA valve. An EGR valve and the thermal vacuum switch are removed and reinstalled in the system; details should be paid to vacuum lines, and sealing should be appropriate.

Careful handling of vacuum lines and proper sealing are required to ensure functionality during the removal and installation of the EGR valve and thermal vacuum switch.

The EGR system is designed to reduce nitrogen oxide (NOX) emissions by recirculating a small amount of exhaust gas into the combustion cycle to lower peak combustion temperatures, where NOX is formed.

If the diaphragm does not move or moves only with much effort, it is recommended to replace the EGR valve with a new one.

The EGA valve is located on the intake manifold, adjacent to the carburetor.

The purpose of the EGR system is to reduce the emissions of oxides of nitrogen (NOx) from the exhaust.

To check the EGR valve, locate it on the intake manifold, ensure the diaphragm moves freely, and test engine response when manually depressing the diaphragm. Additionally, verify that vacuum reaches the EGR valve and check the thermal vacuum switch's functionality with a vacuum gauge.

With the engine cold, you can reach under the EGR valve and manually push on the diaphragm. Using moderate pressure, you should be able to press the diaphragm up and down within the housing.

The most common cause is a stuck or corroded EGR valve.

The EGR system is designed to reduce nitrogen oxide (NOX) emissions by recirculating a small amount of exhaust gas into the combustion cycle to lower peak combustion temperatures, where NOX is formed.

The EGA valve is located on the intake manifold, adjacent to the carburetor.