Saturn Coupes/Sedans/Wagons 1991-1998 Repair Guide

Exhaust Gas Recirculation System

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OPERATION



The Exhaust Gas Recirculation (EGR) valve is used to allow a controlled amount of exhaust gas to be recirculated into the intake system. This limits peak flame temperature in the combustion chamber so the engine produces less NOx (oxides of nitrogen).

A negative backpressure EGR valve is used to control the amount of exhaust gas which is recirculated. Intake manifold vacuum is supplied directly to the top of the diaphragm to pull open the normally closed valve. Exhaust backpressure pushing against the valve keeps the diaphragm pushed against the bleed hole. When the rpm is high but the throttle is closed, exhaust backpressure becomes negative and the diaphragm is pulled down just enough to uncover the bleed hole. The vacuum on top of the diaphragm leaks off and the valve slowly closes.

The EGR vacuum is controlled by the PCM through a solenoid valve. The PCM energizes or de-energizes the solenoid by providing or withholding ground at the appropriate times. When the solenoid is energized, it prevents vacuum from reaching the EGR valve by venting it to the atmosphere. Once the proper conditions have been met, the PCM removes the ground, thus de-energizing the solenoid and allowing vacuum to open the EGR valve. The valve is open only when the throttle is open more than 4 percent and coolant temperature is above 104°F (40°C) for the DOHC engine with automatic transaxle, or 122°F (50°C) for all others.

TESTING



Vacuum Operated EGR Valve

See Figures 1 and 2

If fault Code 32 is present along with Code 26, troubleshoot Code 26 first and then clear the code memory. Drive the vehicle to see if Code 32 sets again, then proceed to troubleshoot the EGR system. A complete listing of trouble codes can be found later in this section.

If code 32 resets, or a problem is still suspected with the EGR system, test the EGR valve and solenoid as follows:

  1. Make sure the ignition is OFF so that the solenoid is not energized.
  2.  
  3. Disconnect the EGR valve vacuum hose from the solenoid and attach a hand vacuum pump. Apply vacuum and observe the EGR valve for movement. The valve should easily open and vacuum should be held for a minimum of 20 seconds. If the valve does not open, check for damaged, plugged or kinked lines, or for restrictions in the valve vacuum port which would prevent vacuum from opening the valve. Clean restrictions and/or replace the lines or valve, as necessary, to correct the condition.
  4.  
  5. If the valve opened and vacuum held, disconnect the vacuum hose from the EGR valve port and attach the hand vacuum pump directly to the EGR valve. Apply vacuum and observe the valve opening again. While you watch the valve and the vacuum gauge, have an assistant start the engine. The valve should close and vacuum should drop immediately as the engine is started. If this does not occur, remove the valve and either clean the plugged passages or replace the faulty valve.
  6.  
  7. If the valve is working, but system trouble is still suspected, test the solenoid. Turn the ignition OFF and reconnect the vacuum lines to the valve and solenoid.
  8.  
  9. Disconnect the solenoid vacuum line from the throttle body and attach the vacuum pump to the line. Apply vacuum to the lines and observe to see if it holds for at least 20 seconds. If the vacuum does not hold, replace the leaking lines or the bad solenoid, whichever was at fault. Remember, the non-energized solenoid should allow the EGR valve to open.
  10.  
  11. A suspected bad solenoid can also be checked using an ohmmeter. Resistance across the solenoid' terminals should be 22-42 ohms.
  12.  



Click image to see an enlarged view

Fig. Fig. 1: Apply vacuum to the EGR valve to see if it will open properly



Click image to see an enlarged view

Fig. Fig. 2: Apply vacuum to the throttle body vacuum line to see if the solenoid is causing a problem with the EGR system

Linear EGR Valve
  1. Connect a scan tool to the DLC connector, below the left side of the instrument panel.
  2.  
  3. With the engine running, open the linear EGR valve to the full open position.
  4.  
  5. If the engine runs rough when the valve is open, check the malfunction diagnostic history. Also, check the EGR pintle for excessive carbon build-up.
  6.  
  7. If the engine does not run rough with the valve fully open, check to see if the pintle position increases when the valve is open. If this happens, remove and check the valve for foreign material build-up. Clean or replace the linear EGR valve if necessary.
  8.  

REMOVAL & INSTALLATION



EGR Solenoid

See Figure 3

  1. As an added safety precaution, you may wish to disable the air bag(s), if equipped. refer to Chassis Electrical for disabling procedure.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the air cleaner assembly for SOHC engines or the air intake tube and resonator for DOHC engines.
  6.  
  7. Unplug the solenoid electrical connector and vacuum line.
  8.  
  9. Unfasten the solenoid attaching bolt, then remove the solenoid from the engine.
  10.  

To install:
  1. Install the solenoid and tighten the bolt to 89 inch lbs. (10 Nm) for DOHC engines, or to 18 ft. lbs. (25 Nm) for SOHC engines.
  2.  
  3. Connect the vacuum lines, then install the electrical connector and push until it clicks firmly into place.
  4.  
  5. Install the air cleaner assembly or the intake tube and resonator, as applicable.
  6.  
  7. Connect the negative battery cable.
  8.  
  9. If necessary, enable the air bag(s). refer to Chassis Electrical .
  10.  



Click image to see an enlarged view

Fig. Fig. 3: Loosen the EGR solenoid attaching bolt, then remove the solenoid from the engine

Vacuum Operated EGR Valve

See Figures 4, 5 and 6

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner assembly for SOHC engines or the air intake tube and resonator for DOHC engines.
  4.  
  5. Disconnect the vacuum line from the valve.
  6.  
  7. For SOHC engines, remove the intake manifold brace and fuel line clips, in order to access the EGR valve fasteners.
  8.  
  9. Remove the valve fasteners.
  10.  
  11. Remove the valve from the vehicle, then remove and discard the gasket from the mating surfaces.
  12.  

To install:
  1. Inspect the EGR passages on the engine for excessive deposits and remove using a screwdriver or length of odometer cable. Use a wire brush or wheel to remove deposits from the EGR valve and engine mounting surfaces. Make sure the surfaces are free of scores or cracks.
  2.  
  3. Install the valve using a new gasket and tighten the fasteners to 19 ft. lbs. (25 Nm). For the SOHC engine, install the intake manifold brace and the fuel line clips.
  4.  
  5. Connect the vacuum hose to the valve.
  6.  
  7. Install the air cleaner assembly or the air intake tube and resonator, as applicable.
  8.  
  9. Connect the negative battery cable.
  10.  



Click image to see an enlarged view

Fig. Fig. 4: Disconnect the vacuum line from the EGR valve



Click image to see an enlarged view

Fig. Fig. 5: Remove the EGR valve mounting fasteners



Click image to see an enlarged view

Fig. Fig. 6: Remove the valve from the vehicle, then remove and discard the mounting gasket

Linear EGR Valve
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner/intake tube assembly.
  4.  
  5. Disconnect the EGR valve wiring harness.
  6.  
  7. Remove the valve fasteners.
  8.  
  9. Remove the valve from the vehicle, then remove and discard the gasket from the mating surfaces.
  10.  

To install:
  1. Inspect the EGR passages on the engine for excessive deposits and remove using a screwdriver or length of odometer cable. Use a wire brush or wheel to remove deposits from the EGR valve and engine mounting surfaces. Make sure the surfaces are free of scores or cracks.
  2.  
  3. Install the valve using a new gasket and tighten the fasteners to 19 ft. lbs. (25 Nm).
  4.  
  5. Connect the EGR valve wiring harness to the valve.
  6.  
  7. Install the air cleaner/intake tube assembly.
  8.  
  9. Connect the negative battery cable.
  10.  

 
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