ParkAvenue 1997-1999

Exhaust Gas Recirculation System

Print

Description & Operation



The 1992 3.8L (VIN L) engine does not use an EGR valve.

The Exhaust Gas Recirculation (EGR) system is used to reduce oxides of nitrogen (NOx) emission levels caused by high combustion chamber temperatures. This is accomplished by the use of an EGR valve which opens, under specific engine operating conditions, to admit a small amount of exhaust gas into the intake manifold, below the throttle plate. The exhaust gas mixes with the incoming air charge and displaces a portion of the oxygen in the air/fuel mixture entering the combustion chamber. The exhaust gas does not support combustion of the air/fuel mixture but it takes up volume, the net effect of which is to lower the temperature of the combustion process. This lower temperature also helps control detonation.

The EGR valve is a mounted on the intake manifold and has an opening into the exhaust manifold. Except for the digital and linear versions, the EGR valve is opened by manifold vacuum to permit exhaust gas to flow into the intake manifold. With the digital and linear versions, the EGR valve is purely electrical and uses solenoid valves to open the flow passage. If too much exhaust gas enters, combustion will not occur. Because of this, very little exhaust gas is allowed to pass through the valve. The EGR system will be activated once the engine reaches normal operating temperature and the EGR valve will open when engine operating conditions are above idle speed and below Wide Open Throttle (WOT). On California vehicles equipped with a Vehicle Speed Sensor (VSS), the EGR valve opens when the VSS signal is greater than 2 mph (3.2 kph). The EGR system is deactivated on vehicles equipped with a Transmission Converter Clutch (TCC) when the TCC is engaged.



Click image to see an enlarged view

Fig. The EGR valve will probably have an identification number stamped into it

Too much EGR flow at idle, cruise, or during cold operation may result in the engine stalling after cold start, the engine stalling at idle after deceleration, vehicle surge during cruise and rough idle. If the EGR valve is always open, the vehicle may not idle. Too little or no EGR flow allows combustion temperatures to get too high which could result in spark knock (detonation), engine overheating and/or emission test failure.

There are three basic types of systems as described below, differing in the way EGR flow is modulated.

Digital EGR Valve

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

The digital EGR valve, used on all 1989-93 EGR-equipped engines, is designed to control the flow of EGR independent of intake manifold vacuum. The valve controls EGR flow through 3 solenoid-opened orifices, which increase in size, to produce 7 possible combinations. When a solenoid is energized, the armature with attached shaft and swivel pintle is lifted, thereby opening the orifice.

The digital EGR valve is opened by the ECM, grounding each solenoid circuit individually. The flow of EGR is regulated by the ECM which uses information from the Engine Coolant Temperature (ECT) sensor, Throttle Position (TP) sensor and Manifold Absolute Pressure (MAP) sensor to determine the appropriate rate of flow for a particular engine operating condition.



Click image to see an enlarged view

Fig. Digital EGR valve components

Linear EGR Valve

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

The linear EGR valve, used on 1994-99 engines, is designed to accurately supply EGR to an engine, independent of intake manifold vacuum. The valve controls EGR flow from the exhaust to the intake manifold through an orifice with a PCM-controlled pintle. During operation, the PCM controls pintle position by monitoring the pintle position feedback signal. The PCM uses information from the Engine Coolant Temperature (ECT) sensor, Throttle Position (TP) sensor and Mass Air Flow (MAF) sensor to determine the appropriate rate of flow for a particular engine operating condition.



Click image to see an enlarged view

Fig. All 1994-99 vehicles are equipped with a linear EGR valve - 3.8L (VIN L) shown

Negative Backpressure EGR Valve

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

The negative backpressure EGR valve, used on early model vehicles, will be marked with an "N" stamped on the top side of the valve by the part number, varies the amount of exhaust gas flow into the intake manifold depending on manifold vacuum and variations in exhaust backpressure. An air bleed valve, located inside the EGR valve assembly acts as a vacuum regulator. The bleed valve controls the amount of vacuum in the vacuum chamber by bleeding vacuum to outside air during the open phase of the cycle. The diaphragm on the valve has an internal air bleed hole which is held closed by a small spring when there is no exhaust backpressure. Engine vacuum opens the EGR valve against the pressure of a spring. When manifold vacuum combines with negative exhaust backpressure, the vacuum bleed hole opens and the EGR valve closes. This valve will open if vacuum is applied with the engine not running.



Click image to see an enlarged view

Fig. The negative backpressure EGR valve is vacuum controlled



Click image to see an enlarged view

Fig. Cross-sectional view of the negative backpressure EGR valve

Removal & Installation



EGR Solenoid

An EGR solenoid is used to control the EGR valve operation on vehicles without a digital EGR valve.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner, as required.
  4.  
  5. Disconnect the electrical connector at the solenoid.
  6.  
  7. Disconnect the vacuum hoses.
  8.  
  9. Remove the retaining bolts and the solenoid.
  10.  
  11. Remove the filter, as required.
  12.  

To install:

  1. If removed, install the filter.
  2.  
  3. Install the solenoid and retaining bolts.
  4.  
  5. Connect the vacuum hoses.
  6.  
  7. Connect the electrical connector.
  8.  
  9. If removed, install the air cleaner.
  10.  
  11. Connect the negative battery cable.
  12.  

EGR Valve
Digital Valve

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

  1. Disconnect the negative battery cable.
  2.  
  3. If necessary, remove the cosmetic cover/sight shield.
  4.  



Click image to see an enlarged view

Fig. Twist to unlock, then remove the EGR cover by lifting it straight up

  1. Detach the electrical connector from the solenoid.
  2.  



Click image to see an enlarged view

Fig. Remove the EGR valve electrical connector retaining clip ...



Click image to see an enlarged view

Fig. ... then detach the electrical connector

  1. Remove the 2 base-to-flange bolts, then remove the digital EGR valve.
  2.  



Click image to see an enlarged view

Fig. The digital EGR valve is mounted to the flange with 2 bolts (see arrows)



Click image to see an enlarged view

Fig. After removing the bolts, lift the EGR valve from the mounting flange

  1. Remove and discard the EGR gasket. Thoroughly clean the gasket mating surfaces.
  2.  



Click image to see an enlarged view

Fig. Remove and discard the old EGR valve gasket



Click image to see an enlarged view

Fig. Use a scraper to carefully clean the old gasket material from the flange



Click image to see an enlarged view

Fig. Make sure to also clean the EGR valve's gasket mating surface

To install:

  1. Install a new gasket, then position the EGR valve over the gasket.
  2.  
  3. Install the 2 base-to-flange bolts. Tighten to 17 ft. lbs. (4 Nm) for 1990-91 vehicles, or to 2 ft. lbs. (30 Nm) for 1992-93 vehicles.
  4.  
  5. If removed, install the cosmetic cover/sight shield.
  6.  
  7. Connect the negative battery cable.
  8.  

Linear EGR Valves

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

  1. Disconnect the negative battery cable.
  2.  
  3. Detach the EGR valve electrical connector.
  4.  
  5. Unfasten the 2 base-to-flange bolts/nuts, then remove the EGR valve from the vehicle.
  6.  
  7. Remove and discard the gasket from the EGR valve adapter.
  8.  



Click image to see an enlarged view

Fig. Exploded view of the linear EGR valve - 3.8L (VIN K) engine



Click image to see an enlarged view

Fig. Location of the EGR valve mounting - 3.8L (VIN 1) engine

To install:

  1. Position a new gasket on the EGR valve adapter.
  2.  
  3. Install the EGR valve and secure with the retaining bolts/nuts. Tighten the retainers to 22 ft. lbs. (30 Nm).
  4.  
  5. Attach the EGR valve electrical connector.
  6.  
  7. Connect the negative battery cable.
  8.  

Negative Backpressure Valve

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner assembly.
  4.  
  5. Tag and disconnect the necessary hoses and wiring to gain access to the EGR valve.
  6.  
  7. Unfasten the EGR valve retaining bolts, then remove the EGR valve.
  8.  
  9. Remove and discard the gasket.
  10.  
  11. Carefully buff the exhaust deposits from the mounting surface and around the valve using a wire wheel.
  12.  
  13. Remove deposits from the valve outlet.
  14.  
  15. Clean the mounting surfaces of the intake manifold and valve assembly.
  16.  

To install:

  1. Install a new EGR gasket.
  2.  
  3. Position the EGR valve to the manifold, then secure with the retaining bolts. Tighten to 16 ft. lbs. (2 Nm).
  4.  
  5. Connect the wiring and hoses.
  6.  
  7. Install the air cleaner assembly.
  8.  
  9. Connect the negative battery cable.
  10.  

Testing



Digital EGR Valve

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

This system must be checked using a Scan tool, or similar device. Steps 4, 5 and 6 must be done very quickly, as the ECM will adjust the idle air control valve to adjust idle speed.

  1. Using a Scan tool or equivalent, check for trouble codes and solve those problems first, referring to appropriate chart elsewhere in this Section.
  2.  
  3. Using the Scan tool, select "EGR CONTROL."
  4.  
  5. Run the engine to normal operating temperature, and allow the engine to idle for 2 minutes.
  6.  
  7. Energize EGR SOL #1; engine rpm should drop slightly.
  8.  
  9. Energize EGR SOL #2; the engine should have a rough idle.
  10.  
  11. Energize EGR SOL #3; the engine should idle rough or stall.
  12.  
  13. If all tests were as specified, the system is functioning properly.
  14.  
  15. If not, check the EGR valve, pipe, adapter, gaskets, fittings, and all passages for damage, leakage or plugging. If all is OK, replace the EGR valve assembly.
  16.  
  17. You can also check the resistance between the terminals using an ohmmeter, as follows:
    1. Turn the EGR valve cap to unlock it, then lift it off the top of the valve.

      Click image to see an enlarged view

      Fig. Twist the cap of the EGR valve to unlock, then lift off the cover

    2.  
    3. Remove the EGR valve electrical connector locking clip, then detach the electrical connector.

      Click image to see an enlarged view

      Fig. Remove the locking clip from the EGR valve electrical connector ...



      Click image to see an enlarged view

      Fig. ... then unplug the valve's electrical connector

    4.  
    5. Use an ohmmeter, set to the ohms scale, to measure the resistance. Compare with the following specifications:
    6.  

  18.  
  19. Terminals A and D: 20-30 ohms
  20.  
  21. Terminals B and D: 20-30 ohms
  22.  
  23. Terminals C and D: 10-17 ohms
  24.  



Click image to see an enlarged view

Fig. Digital EGR valve terminal identification



Click image to see an enlarged view

Fig. Measure the resistance between EGR valve terminals A and D (circled in inset). In this case, the reading is 3.4 ohms



Click image to see an enlarged view

Fig. Check the resistance between terminals B and D (circled in inset). In this case, the reading is 3.1 ohms



Click image to see an enlarged view

Fig. Measure the resistance between terminals C and D (circled in inset). In this case, the reading is 12.8 ohms

Linear EGR Valve

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

To check this system, refer to the accompanying diagnostic chart for 1994-98 3.8L engines.



Click image to see an enlarged view

Fig. Linear EGR system flow check - 1994-99 vehicles

Negative Backpressure EGR Valve

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

  1. Inspect all passages and moving parts for plugging, sticking and deposits.
  2.  
  3. Inspect the entire system (hoses, tubes, connections, etc.) for leakage. Replace any part that is leaking, hardened, cracked, or melted.
  4.  
  5. Run the engine to normal operating temperature, and allow the engine to idle for 2 minutes. Quickly accelerate the engine to 2,500 rpm. Visible movement of the EGR stem should occur indicating proper system function. If no movement occurs, check the vacuum source and hose.
  6.  
  7. To determine if gas is flowing through the system, connect a vacuum pump to the valve.
  8.  
  9. With the engine idling, slowly apply vacuum. Engine speed should start to decrease when applied vacuum reaches 3 in. Hg. The engine speed may drop quickly and could even stall; this indicated proper function.
  10.  
  11. If engine speed does not drop off, remove the EGR valve and check for plugged passages. If everything checks out, replace the valve.
  12.  

 
label.common.footer.alt.autozoneLogo