GMC 1997254 Solenoid,EGR Vacuum Regulator Valve

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EGR system is designed to reduce NOx emissions by recirculating some of the exhaust gases back into the intake manifold in order to decrease combustion temperatures, hence lowering NOx compound formation. In the early models (1988-1995), this system consists of an EGR valve, an EGR solenoid valve and the Electronic Control Module (ECM). When cruising on a highway for instance, ECM signals open EGR solenoid valve which allows vacuum from intake manifold to reach EGR valve that opens up thus allowing flow of exhaust gas into intake manifold. The later models (1996-2000) have an electronic EGR valve controlled by PCM, which can regulate EGR flow accurately based on engine operating conditions observed through EGR position sensor. Early model's problems with the EGR system are often characterized by poor idling and may be traced back to a wrong operation of the ECM or malfunctioning parts such as misrouted vacuum hoses or defective parts themselves like EGR solenoid valves or even the most complicated valving systems of vehicles sold in dealerships. It is important to inspect vacuum hoses and replace any that are damaged or misrouted. While testing entails applying vacuum to the idle engine's EGR valve; if there is no change in idle or little one at best then it might call for replacement of the same. For testing purposes on vehicles below 8500 GVW concerning EGR solenoid valves, ignition should be off with vacuum applied; otherwise replacement must be done while over 8500 GVW vehicle's during test should have ignition turned on (engine not running). Disconnecting electric connector and retesting is necessary if the electrical signal causes movement; replacing a solenoid valve if it does not move means that it has gone bad for all intents and purposes other than safety reasons related thereto. On late models (1996-2000), complete testing requires a scan tool, but there are some limited tests that can be done to confirm system operation if it is obviously failed. These involve checking the voltage supply and ground circuits for the EGR valve position sensor with a voltmeter indicating approximately 5.0 volts when the ignition key is on. If this is not true, then PCM-to-EGR valve circuits should be checked with a possible diagnosis of PCM by dealer service department or qualified repair shop if found to be okay. Checking continuity of EGR valve would require ohmmeter for the purpose of evaluating both EGR valve position sensor and EGR solenoid coil. Once an open circuit has been detected, professional diagnosis becomes necessary. In order to replace the EGR valve, access must be gained; electrical connectors disconnected (if equipped); mounting bolts removed and then remove gaskets from the EGR value during removal as new ones are applied after reinstallation. When doing replacement of EGR pipe, start by removing bracket bolt then loosen fittings at each end of pipe before removing it; afterwards install pipe with fittings tightened and bracket bolt secured again.

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

Issues with the EGR system in early models often manifest as rough idling. These issues can result from a malfunctioning EGR valve, EGR solenoid valve, misrouted vacuum hoses, or a faulty ECM.

With the engine cold, you can push on the EGR valve diaphragm using moderate pressure. The diaphragm should move easily with finger pressure. If it doesn't move or moves with much effort, the EGR valve should be replaced.