The Exhaust Gas Recirculation (EGR) system is designed to reduce Oxides of Nitrogen (NO x ) by recirculating exhaust gas through the EGR valve and into the intake manifold and combustion chambers.
The EGR Valve is controlled by the Powertrain Control Module (PCM) that relies on feedback from various sensors. The PCM contains a memory for ideal EGR Valve operation and lift suited to various operating conditions.
The amount of exhaust gas that is reintroduced into the combustion cycle is determined by several factors, such as: engine speed, engine vacuum, exhaust system backpressure, coolant temperature, and throttle position.
The EGR valve is vacuum operated and via an inline solenoid. The EGR vacuum diagram for a particular year and model of vehicle is displayed on the Vehicle Emission Control Information (VECI) label found on the underside of the hood.
- Disconnect and plug the vacuum supply hose from the EGR valve.
- Start the engine, then apply the parking brake, block the rear wheels and position the transmission in Neutral. Allow the engine to reach normal operating temperature.
Using a hand-held vacuum pump, slowly apply 8 in. Hg (26 kPa) of vacuum to the EGR valve nipple.
- If the idle speed drops more than 100 rpm with the vacuum applied and returns to normal after the vacuum is removed, the EGR valve is OK.
- If the idle speed does not drop more than 100 rpm with the vacuum applied and return to normal after the vacuum is removed, inspect the EGR valve for a blockage; clean it if a blockage is found. Replace the EGR valve if no blockage is found, or if cleaning the valve does not remedy the malfunction.
REMOVAL & INSTALLATION
- Disconnect the negative battery cable.
- On models equipped with the EGR lift sensor, remove the EGR lift sensor electrical connector.
- Remove the vacuum hose from the EGR valve.
- Remove the EGR valve mounting fasteners, then separate the valve from the intake manifold.
- Remove and discard the old EGR valve gasket. Clean the gasket mating surfaces on the valve and the intake manifold.
- Install the EGR valve, along with a new gasket, on the upper intake manifold, then install and tighten the mounting bolts
- Connect the vacuum hose to the EGR valve.
- Connect the negative battery cable.