The Exhaust Gas Recirculation (EGR) system recycles part of the exhaust gases into the combustion chamber to lower the peak combustion temperatures. By lowering peak temperatures, a reduction in Oxides of Nitrogen (NOx) is obtained.
The system consists of an EGR valve, thermo valve, and a catalytic converter. California models use an EGR Control Solenoid Valve and an EGR Temperature Sensor.
The EGR valve is operated by engine vacuum. It receives exhaust gasses through one port and as indicated by the ECM, allows exhaust gasses to flow into the combustion chambers through a second port.
The Thermo Vacuum Valve (TVV) is connected inline between the EGR valve and the vacuum supply. The valve is threaded into the intake manifold coolant passage. The valve functions as a temperature switch to stop the vacuum signal to the EGR valve.
The control solenoid valve functions much like the thermo valve but is controlled by the ECM instead of coolant temperature. The valve functions to stop the vacuum signal to the EGR valve.
See Figures 1, 2, 3, 4 and 5EGR Valve
- Inspect the EGR valve for sticking or carbon deposits.
- Clean the valve with solvent and ensure that the valve is fully seated on the contact surface.
- Connect a hand vacuum pump to the valve and apply 19.4 in. HG of vacuum. Check that vacuum is held.
- Release the vacuum and apply 1.7 in. Hg of vacuum. Blow air into one passage of the valve. Air should not blow through.
- Increase the vacuum to 7.5 in. Hg and blow air into the passage again. Air should blow through.
- Replace the EGR valve if it fails to function properly.
- Connect a hand vacuum pump to the thermo valve nipple.
- Apply a vacuum with a hand vacuum pump.
- At coolant temperatures below 122°F (50°C), the vacuum should not hold.
- At coolant temperatures above 176°F (80°C), the vacuum should hold.
- Replace the thermo valve if not functioning properly.
- Tag and disconnect the vacuum lines and harness connector from the valve.
- Connect a hand vacuum pump to the nipple where the green striped hose was connected and draw vacuum.
Connect a 12 volt source to the solenoid and check as follows:
- With voltage applied, vacuum should hold.
- With voltage disconnected, vacuum should bleed off.
- Measure the resistance between the terminals of the solenoid valve.
- Resistance should be 33-44 ohms at 68°F (20°C).
EGR Temperature Sensor (California)
See Figure 6
- Remove the EGR temperature sensor from the EGR valve and place in a bucket of water with a thermometer.
- Heat the water to 122°F (50°C) and measure the resistance across the sensor terminals. Resistance should be 60-83 ohms.
- Raise the temperature of the water to 212°F (100°C) and measure the resistance again. Resistance should drop to 11-14 ohms.
- Replace the EGR temperature sensor if defective.
REMOVAL & INSTALLATION
See Figures 7 and 8EGR Valve
- Locate the EGR valve on the engine.
- Label and disconnect the vacuum line.
- Remove the EGR mounting bolts
- Remove the EGR valve.
It may be necessary to pry the EGR valve from the engine.To Install:
- Install the EGR valve using a new gasket.
- Install the EGR mounting bolts and tighten to 11-16 ft. lbs. (15-22 Nm).
- Connect the vacuum line.
- Drain the coolant.
- Disconnect the thermo valve vacuum lines.
- Remove the valve from the engine.
- Coat the valve with sealant and install. Tighten valve to 14-16 ft. lbs. (20-40 Nm).
- Connect the thermo valve vacuum lines.
- Refill the engine with coolant.
EGR Temperature Sensor (California)
- Disconnect the temperature sensor electrical harness.
- Remove the sensor from the engine.
- Coat the sensor with antiseize and install. Tighten sensor to 7-9 ft. lbs. (10-12 Nm).
- Connect the temperature sensor electrical harness.