GM Corsica/Beretta 1988-1996 Repair Guide

Exhaust Gas Recirculation (EGR) System

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The 2.3L (VIN A) engine does not use an EGR valve.

The 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.

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

Integrated Electronic EGR Valve

See Figure 1



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Fig. Fig. 1: The integrated electronic EGR valve is used on all 1988-89 2.8L engines

The integrated electronic EGR valve, used on 1988-89 2.8L engines, functions like a port valve with a remote vacuum regulator, except the regulator and a pintle position sensor are sealed in the black plastic cover. The regulator and position sensor are not serviceable items; there is a serviceable filter that provides fresh air to the regulator, along side the vacuum tube.

This valve has a vacuum regulator, to which the ECM provides variable current. This current produces the desired EGR flow using inputs from the manifold air temperature sensor, coolant temperature sensor and engine rpm.

Negative Backpressure EGR Valve

See Figure 2

The negative backpressure EGR valve, used on the 2.0L and 1990-95 2.2L engines, 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.



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Fig. Fig. 2: The negative backpressure EGR valve is used on the 1988-95 2.0L and 2.2L engines

Digital EGR Valve

See Figure 3



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Fig. Fig. 3: All 1990-91 3.1L engines, utilize the digital EGR valve

The digital EGR valve, used on all 1990-95 3.1L 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, 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 Coolant Temperature Sensor (CTS), Throttle Position Sensor (TPS) and Manifold Absolute Pressure (MAP) sensor to determine the appropriate rate of flow for a particular engine operating condition.

Linear EGR Valve

The linear EGR valve, used on the 1996 2.2L and 3.1L engines, is designed to accurately apply 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 the Mass Air Flow (MAF) sensor to determine the appropriate rate of flow for a particular engine operating condition.

COMPONENT TESTING



See Figures 4 through 11

For EGR testing, please refer to the accompanying charts. Note that some testing procedures require the use of a Tech 1® or equivalent scan tool. Also, when perform the digital EGR system test, the steps must be performed quickly, as the ECM will adjust the idle air control valve to compensate for idle speed.



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Fig. Fig. 4: Integrated Electronic EGR system check - 1988-89 2.8L engines



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Fig. Fig. 5: Negative backpressure EGR system check - 1990-91 2.2L engines



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Fig. Fig. 6: Negative backpressure EGR system check - 1992-93 2.2L engines



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Fig. Fig. 7: Negative backpressure EGR system circuits - 1994-95 2.2L engines



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Fig. Fig. 8: Negative backpressure EGR system check (1 of 2) - 1994-95 2.2L engines



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Fig. Fig. 9: Negative backpressure EGR system check (2 of 2) - 1994-95 2.2L engines



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Fig. Fig. 10: Digital EGR system check - 1990-91 3.1L engines



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Fig. Fig. 11: Digital EGR system check - 1992-93 3.1L engines

REMOVAL & INSTALLATION



EGR Valve
2.0L AND 1990-95 2.2L ENGINES

See Figure 12

  1. Disconnect the negative battery cable.
  2.  
  3. If necessary for access, remove the air cleaner assembly.
  4.  
  5. Disconnect the EGR vacuum hose from the valve.
  6.  
  7. Unfasten the EGR retaining bolts, then remove the EGR valve from the manifold.
  8.  
  9. Remove and discard the EGR valve gasket.
  10.  
  11. Inspect the EGR manifold passage and clean any excessive build-up of deposits. Make sure all loose particles are completely removed.
  12.  
  13. With a wire brush or wheel, carefully buff the exhaust deposits from the mounting surface and around the valve. Look for exhaust deposits in the valve outlet and remove with a suitable tool.
  14.  
  15. Clean the mounting surfaces of the intake manifold and valve assembly.
  16.  



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Fig. Fig. 12: Exploded view of the negative backpressure EGR valve mounting - 2.0L and 2.2L engines

To install:
  1. Position a new gasket on the mounting flange, then install the EGR valve on the intake manifold.
  2.  
  3. Install the retaining bolts and tighten to 11-18 ft. lbs. (15-25 Nm).
  4.  
  5. Attach the vacuum hose to the valve.
  6.  
  7. Connect the negative battery cable.
  8.  

2.8L ENGINE

See Figure 13

  1. Disconnect the negative battery cable.
  2.  
  3. Detach the EGR vacuum hose from the valve.
  4.  
  5. Unplug the electrical connector.
  6.  
  7. Disconnect the EGR tube from the exhaust manifold.
  8.  
  9. Remove the three EGR mounting nuts from the plenum studs.
  10.  
  11. Remove the EGR tube from the valve by removing the two bolts.
  12.  
  13. Inspect the EGR manifold passage and clean any excessive build-up of deposits. Make sure all loose particles are completely removed.
  14.  
  15. With a wire brush or wheel, clean the exhaust deposits from the mounting surface and around the valve. Look for exhaust deposits in the valve outlet and remove with a suitable tool.
  16.  
  17. Clean the mounting surfaces of the intake manifold and valve assembly.
  18.  



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Fig. Fig. 13: Integrated electronic EGR valve mounting and related components - 2.8l engines

To install:
  1. Install the EGR tube to the EGR valve using a new gasket and tighten to 19 ft. lbs. (26 Nm).
  2.  
  3. Install the EGR valve and tube assembly to the plenum using a new gasket.
  4.  
  5. Tighten the bolts to 19 ft. lbs. (26 Nm).
  6.  
  7. Install the EGR tube to the exhaust manifold and tighten to 19 ft. lbs. (26 Nm)
  8.  
  9. Attach the electrical connector.
  10.  
  11. Install the vacuum hose to the valve.
  12.  
  13. Connect the negative battery cable.
  14.  

1990-95 3.1L ENGINE

See Figure 14

  1. Disconnect the negative battery cable.
  2.  
  3. Detach the electrical connector from the solenoid.
  4.  
  5. Remove the 2 base-to-flange bolts, then remove the digital EGR valve from the vehicle. Remove the gasket, inspect for damage, and replaced as necessary.
  6.  



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Fig. Fig. 14: Exploded view of the digital EGR valve mounting - 3.1L engines

To install:
  1. Position the EGR gasket on the pad, aligning it with the holes.
  2.  
  3. Place the EGR valve on the gasket, then install the 2 base to flange bolts finger-tight, aligning the holes through the valve and pad of the upper intake manifold and into the pipe assembly.
  4.  
  5. For 1990-93 vehicles, tighten the bolts in two steps in the following sequence:
    1. Step 1: tighten the long bolt to 11 ft. lbs. (15 Nm) and the short bolt to 11 ft. lbs. (15 Nm).
    2.  
    3. Step 2: tighten the long bolt to 30 ft. lbs. (22 Nm) and the short bolt to 30 ft. lbs. (22 Nm).
    4.  

  6.  
  7. For 1994-95 vehicles, tighten the mounting bolts to 18 ft. lbs. (25 Nm).
  8.  
  9. Attach the electrical connector to the solenoid.
  10.  
  11. Connect the negative battery cable.
  12.  

1996 2.2L AND 3.1L ENGINES

See Figures 15 through 20

  1. Disconnect the negative battery cable.
  2.  
  3. For 2.2L engines, remove the air cleaner outlet resonator.
  4.  
  5. Detach the EGR valve electrical connector.
  6.  



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Fig. Fig. 15: Unplug the EGR valve electrical connector

  1. Unfasten the retaining bolts, then remove the EGR valve from the vehicle. Remove the gasket, inspect for damage and replace, if necessary.
  2.  



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Fig. Fig. 16: Remove the EGR valve mounting bolts



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Fig. Fig. 17: Remove the EGR valve from its mounting flange ...



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Fig. Fig. 18: ... then remove the gasket, inspect for damage and replace if necessary

  1. Thoroughly clean the gasket mating surfaces, as even a small amount of debris may cause a Diagnostic Trouble Code (DTC) to set.
  2.  



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Fig. Fig. 19: The linear EGR valve on the 1996 2.2L engine is secured with 2 retaining bolts



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Fig. Fig. 20: Exploded view of the linear EGR valve - 1996 3.1L engines

To install:
  1. Position the EGR gasket on the mounting pad, then place the valve over the gasket.
  2.  
  3. Install the retaining bolts and tighten to 16-22 ft. lbs. (22-30 Nm) for 2.2L engines. For 3.1L engines, tighten the retaining bolts to 22 ft. lbs. (30 Nm).
  4.  
  5. Attach the EGR valve electrical connector.
  6.  
  7. If removed, install the air cleaner outlet resonator.
  8.  
  9. Connect the negative battery cable.
  10.  

EGR Control Valve Relay Solenoid and Injector Valve
2.2L ENGINE

See Figure 21

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the MAP sensor, as outlined in this section.
  4.  
  5. Detach the electrical connector from the solenoid.
  6.  
  7. Tag and disconnect the vacuum hoses.
  8.  
  9. Unfasten the retaining screw, then remove the EGR solenoid.
  10.  



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Fig. Fig. 21: Exploded view of the EGR control valve relay solenoid and injector valve, used on some 2.2L engines

To install:
  1. Install the solenoid and bracket and tighten the screw to 17 ft. lbs. (24 Nm) for 1992 vehicles or to 22 ft. lbs. (30 Nm) for 1993-95 vehicles. Do NOT overtighten the retainers.
  2.  
  3. Connect the vacuum hoses, as tagged during removal.
  4.  
  5. Attach the electrical connector to the solenoid.
  6.  
  7. Install the seal on the MAP sensor, then install the MAP sensor and tighten the screws to 27 inch lbs. (3 Nm).
  8.  
  9. Connect the negative battery cable.
  10.  

 
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