GM 12576918 Valve,EGR

Common engine problems associated with the EGR system include rough idling or stalling at idle, rough engine performance during light throttle application, and stalling during deceleration.

The EGR (Exhaust Gas Recirculation) system is designed to reduce nitrogen oxide emissions that result from high combustion temperatures by controlling the amount of exhaust gases that enter the fuel/air mixture, thereby lowering combustion temperatures.

The EGR system meters exhaust gases into the engine's induction system through passages in the intake manifold. It regulates the amount of exhaust gas admitted into the engine in response to various engine operating conditions.

In carbureted and throttle body injection engines, the EGR valve is typically diaphragm-operated and controlled by a vacuum source. In contrast, in central multiport and sequential fuel injection engines, it is electronically controlled without vacuum.

In early models, the EGR system includes an EGR valve, an EGR solenoid valve, and the Electronic Control Module (ECM). The ECM signals the EGR solenoid valve to open under specific conditions, allowing intake manifold vacuum to reach the EGR valve, which then opens, permitting exhaust gas flow into the intake manifold.

For more information on the EGR system, you can look for additional resources.

Oxides of nitrogen, or NOx, are compounds formed in combustion chambers when oxygen and nitrogen mix together. They are a natural byproduct of high combustion chamber temperatures.

The filter in the VRV should be cleaned at regular intervals. It can be cleaned with a soapy solution and then reinstalled.

For late models, complete testing requires a scan tool. However, limited tests can be conducted to verify system operation in case of obvious failure. This includes checking voltage supply and ground circuits to the EGR valve position sensor, where approximately 5.0 volts should be indicated on the voltmeter with the ignition key on. If not, the PCM-to-EGR valve circuits should be examined, and if found to be in good condition, the PCM should be diagnosed by a dealer service department or qualified repair shop.

The EGR system meters exhaust gases into the engine's induction system through passages in the intake manifold. It regulates the amount of exhaust gas admitted into the engine in response to various engine operating conditions.

To check the EGR system, start the engine and manually lift the EGR diaphragm. If the engine stalls or the idle drops considerably, it indicates that the EGR valve is operating properly.

To test the vacuum diaphragm of the EGR valve, disconnect the vacuum hose from the EGR valve and apply vacuum using a vacuum pump. The engine should stumble or die, which indicates that the vacuum diaphragm is operating properly.