Exhaust Gas Recirculation (EGR) System OPERATION ,COMPONENT TESTING ,REMOVAL and INSTALLATION?

OPERATION

See Figure 1

The Exhaust Gas Recirculation (EGR) system is designed to reintroduce exhaust gas into the combustion chambers, thereby lowering combustion temperatures and reducing the formation of Oxides of Nitrogen (NO _x ).

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, throttle position. All EGR valves are vacuum operated. The EGR vacuum diagram for your particular vehicle is displayed on the Vehicle Emission Control Information (VECI) label.

The EGR system is a Pressure Feedback EGR (PFE) or Differential PFE (DPFE) system, controlled by the Powertrain Control Module (PCM) and composed of the following components: PFE or DPFE sensor (also referred to as the backpressure transducer), EGR Vacuum Regulator (EVR) solenoid, EGR valve, and assorted hoses and tubing.

Fig. Fig. 1: Typical EGR system schematic

COMPONENT TESTING

See Figures 2, 3 and 4

Fig. Fig. 2: Exploded view of the EGR system and related components for the 2.3L and 2.5L engine

Fig. Fig. 3: Exploded view of the EGR system and related components for the 3.0L engine

Fig. Fig. 4: Exploded view of the EGR system and related components for the 4.0L engine

System Integrity Inspection

Check the EGR system hoses and connections for looseness, pinching, leaks, splitting, blockage, etc. Ensure that the EGR valve mounting bolts are not loose, or that the flange gasket is not damaged. If the system appears to be in good shape, proceed to the EGR vacuum test, otherwise repair the damaged components.

EGR System Vacuum Test

The EVR solenoid has a constant internal leak; this is normal. There may be a small vacuum signal, however, it should be less than 1.0 in. Hg (3.4 kPa) of vacuum.

Start the engine and allow it to run until normal operating temperature is reached. With the engine running at idle, detach the vacuum supply hose from the EGR valve and install a vacuum gauge to the hose. The vacuum reading should be less than 1.0 in. Hg (3.4 kPa) of vacuum. If the vacuum is greater than that specified, the problem may lie with the EVR solenoid.

EVR Solenoid Test

1. Remove the EVR solenoid.
2. Attempt to lightly blow air into the EVR solenoid.
   1. If air blows through the solenoid, replace the solenoid with a new one.
   2. If air does not pass freely through the solenoid, continue with the test.

   
   
3. Apply battery voltage (approximately 1 volts) and a ground to the EVR solenoid electrical terminals. Attempt to lightly blow air, once again, through the solenoid.
   1. If air does not pass through the solenoid, replace the solenoid with a new one.
   2. If air does not flow through the solenoid, the solenoid is OK.

   
   

EGR Valve Function Test

1. Install a tachometer on the engine, following the manufacturer's instructions.
2. Detach the engine wiring harness connector from the Idle Air Control (IAC) solenoid.
3. Disconnect and plug the vacuum supply hose from the EGR valve.
4. Start the engine, then apply the parking brake, block the rear wheels and position the transmission in Neutral.
5. Observe and note the idle speed.

If the engine will not idle with the IAC solenoid disconnected, provide an air bypass to the engine by slightly opening the throttle plate or by creating an intake vacuum leak. Do not allow the idle speed to exceed typical idle rpm.

Fig. Fig. 5: Some EGR valves may be tested using a vacuum pump by watching for diaphragm movement

6. Using a hand-held vacuum pump, slowly apply 5-10 in. Hg (17-34 kPa) of vacuum to the EGR valve nipple.
   1. 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.
   2. 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

PFE/DPFE Sensor

This component is found on all engines, and is also referred to as the backpressure transducer.

1. Disconnect the negative battery cable.
2. Detach and label the wiring harness connector from the PFE/DPFE sensor.
3. Disconnect all of the hoses from the sensor.
4. Remove the mounting nuts, then separate the sensor from the mounting bracket.
5. If necessary, remove the EVR solenoid and the PFE/DPFE mounting bracket from the upper intake manifold.

To install:

6. If removed, install the EVR solenoid and mounting bracket onto the upper intake manifold.
7. If applicable, install the EGR tube heat shield.
8. Position the PFE/DPFE sensor on the mounting bracket, then install and tighten the mounting nuts until snug.
9. Attach all necessary hoses and wiring to the sensor.
10. Connect the negative battery cable.

EGR Vacuum Regulator (EVR) Solenoid

The EVR solenoid is mounted either on the same bracket as the PFE/DPFE sensor, attached to the upper intake manifold, or near the EGR valve on its own bracket.

1. Disconnect the negative battery cable.
2. Label and detach the wiring harness connector from the EVR solenoid.
3. Detach the main emission vacuum control connector from the solenoid.
4. Remove the retaining nuts, then separate the solenoid from the mounting bracket.

To install:

5. Position the solenoid on its mounting bracket and install the retaining nuts.
6. Attach the main emission vacuum control connector and the wiring harness connector to the EVR solenoid.
7. Connect the negative battery cable.

EGR Valve

See Figures 6 and 7

1. Disconnect the negative battery cable.
2. If necessary, remove the air inlet tube from the throttle body and air cleaner housing.
3. Label and detach all vacuum hoses from the EGR valve.
4. Label and detach any electrical wiring harness connectors from the EGR valve.
5. Disconnect the EGR valve-to-exhaust manifold tube from the EGR valve.
6. Remove the EGR valve mounting fasteners, then separate the valve from the upper intake manifold.
7. Remove and discard the old EGR valve gasket, and clean the gasket mating surfaces on the valve and the intake manifold.

Fig. Fig. 6: Cutaway view of a base entry type EGR valve

Fig. Fig. 7: Cutaway view of a side entry type EGR valve

To install:

8. Install the EGR valve, along with a new gasket, on the upper intake manifold, then install and tighten the mounting bolts to 4-22 ft. lbs. (20-30 Nm) on 3.8L engines, or to 106-49 inch lbs. (1-18 Nm) on 5.0L engines.
9. Connect the EGR valve-to-exhaust manifold tube to the valve, then tighten the tube nut to 30 ft. lbs. (41 Nm).
10. Connect all wiring or hoses to the EGR valve.
11. Install the air inlet tube.
12. Connect the negative battery cable.

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