Toyota Celica/Supra 1971-1985 Repair Guide

Exhaust Gas Recirculation (EGR) System

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OPERATION



See Figures 1, 2, 3, 4, 5 and 6



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Fig. Fig. 1: View of the EGR system-1980 20R engines (other carbureted engines similar)



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Fig. Fig. 2: View of the EGR system-1983 22R-EC engine



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Fig. Fig. 3: View of the EGR system-1984 22R-EC engine



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Fig. Fig. 4: View of the EGR system-1985 22R-EC engine



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Fig. Fig. 5: View of the EGR system-1979-81 Supra



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Fig. Fig. 6: View of the EGR system-5M-GE engine

Starting with 1974 models, Exhaust Gas Recirculation (EGR) is used in all California Celicas. All 1975-85 engines use EGR.

In all cases, the EGR valve is controlled by the same computer and vacuum switching valve which is used to operate other emission control system components.

On 18R-C and 20R engines, the EGR valve is operated by vacuum supplied from a port above the throttle blades and fed through the vacuum switching valve.

On all engines there are several conditions, determined by the computer which permit exhaust gas recirculation to take place:

  1. Vehicle speed
  2.  
  3. Engine coolant temperature
  4.  
  5. EGR valve temperature
  6.  
  7. Carburetor flange temperature
  8.  

On 18R-C and 20R engines equipped with EGR, the exhaust gases are carried from the exhaust manifold to the EGR valve and from the EGR valve to the carburetor, via external tubing. The 20R engine has an exhaust gas cooler mounted on the back of the cylinder head.

COMPONENT TESTING



EGR Valve
1974-78 MODELS
  1. Allow the engine to warm up and remove the top from the air cleaner.
  2.  

Do not remove the entire air cleaner assembly.

  1. Disconnect the hose (white tape coded), which runs from the vacuum switching valve to the EGR valve, at its EGR valve end.
  2.  
  3. Remove the intake manifold hose (red coded) from the vacuum switching valve and connect it to the EGR valve. When the engine is at idle, a "hollow" sound should be heard coming from the air cleaner.
  4.  
  5. Disconnect the hose from the EGR valve; the hollow sound should disappear.
  6.  
  7. If the sound doesn't vary, the EGR valve is defective and must be replaced.
  8.  
  9. Reconnect the vacuum hoses as they were originally found. Install the top of the air cleaner.
  10.  

1979-85 MODELS

See Figure 7



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Fig. Fig. 7: When applying vacuum directly to the EGR valve, the engine should stall

  1. Start the engine.
  2.  
  3. Disconnect the vacuum hose leading from the EGR valve.
  4.  
  5. Disconnect the hose coming from the intake manifold and connect it to the empty pipe on the EGR valve.
  6.  
  7. When applying vacuum directly to the EGR valve, the engine should stall, if not, the EGR valve will probably require replacement.
  8.  

EGR Valve Thermo-Sensor
18R-C, 20R AND 5M-GE ENGINES
  1. Disconnect the electrical lead which runs to the EGR valve thermo-sensor.
  2.  
  3. Remove the thermo-sensor from the side of the EGR valve.
  4.  
  5. Heat the thermo-sensor in a pan of water to the following temperature:

    260°deg;F (127°deg;C)-18R-C and 20R engines
     
    248°deg;F (120°deg;C)-5M-GE engines
     

  6.  
  7. Connect an ohmmeter, in series with a 10 ohm resistor, between the thermo-sensor terminal and case (between both terminals on 5M-GE).
  8.  
  9. With the ohmmeter set on the kilo ohm scale, the following reading should be obtained:

    2.55 kilo ohms-18R-C and 20R engines
     
    0.1 kilo ohms-5M-GE engines
     

  10.  
  11. Replace the thermo-sensor if the ohmmeter readings vary considerably from those specified.
  12.  
  13. Install the sensor to the EGR valve and tighten to 15-21 ft. lbs. (20-28 Nm).
  14.  


WARNING
Do not tighten the thermo-sensor with an impact wrench.

EGR Vacuum Modulator

See Figures 8 and 9



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Fig. Fig. 8: Disconnect and plug the ports of the EGR modulator



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Fig. Fig. 9: With the engine running around 2000 rpm, check the air flow in port Q

  1. Disconnect the vacuum hoses from ports P , Q and R of the EGR vacuum modulator.
  2.  
  3. Plug port P and R with your finger or a golf tee.
  4.  
  5. Blow air into port Q , then check that the air passes through to the filter side freely.
  6.  
  7. Start the engine and maintain the engine speed at 2000 rpm.
  8.  
  9. Repeat the test. Check that there is a strong resistance to air flow.
  10.  

Bimetal Vacuum Switching Valve (BVSV)

See Figure 10



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Fig. Fig. 10: Testing the BVSV operation

To check the BVSV on Supras, refer to the evaporative emission controls.

  1. With the engine cold, blow into the inside pipe on the BVSV. The air should come out of the air filter on the end and not from the other pipe.
  2.  
  3. Start the engine and run it until it reaches normal operating temperature.
  4.  
  5. Blow air into the inside pipe again. This time the air should come out of the other pipe and not from the air filter on the end.
  6.  
  7. If the valve is not operating properly, it will probably require replacement.
  8.  

Vacuum Control Valve (VCV)

See Figure 11



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Fig. Fig. 11: Occasionally you should clean the VCV filter to keep it in working order

  1. To check the VCV (1), follow the procedure given in the Evaporative Emissions Control information.
  2.  
  3. Remove the VCV (2) and unscrew the end plate.
  4.  
  5. Remove the filter inside and clean it with compressed air.
  6.  
  7. Assemble the VCV and apply vacuum to the small pipe on the side which has two. The valve should be open.
  8.  
  9. Stop the applied vacuum and check to see that the valve is closed.
  10.  
  11. If the valve is not operating properly it will require replacement.
  12.  

Vacuum Switching Valve (VSV)

See Figure 12



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Fig. Fig. 12: Testing the EGR VSV on a 1980 Celica

  1. Disconnect the electrical plug to the EGR VSV.
  2.  
  3. Connect the VSV terminals to the battery terminals.
  4.  
  5. Blow air into pipe E and check that it comes out of pipe F .
  6.  
  7. Disconnect the battery and then blow air into pipe E again. This time the air should come out of the air filter which is attached to the valve.
  8.  
  9. If the valve is not operating properly it will probably require replacement.
  10.  

Computer

If, after having completed the above tests, the EGR system still doesn't work right but everything else checks out, the fault probably lies in the computer. If this is the case, it is best to have the car checked out by test facility which has the necessary Toyota emission system test equipment.

A good indication that the fault doesn't lie in the EGR system, but rather in the vacuum supply system, would be if several emission control systems were not working properly.

REMOVAL & INSTALLATION



EGR Vacuum Modulator

See Figure 13



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Fig. Fig. 13: Unscrew the vented top plate and remove the filter

  1. Tag and disconnect all hoses leading form the vacuum modulator.
  2.  
  3. Remove the vacuum modulator.
  4.  
  5. Unscrew the vented top plate and remove the filter.
  6.  
  7. Check the filter for any contamination or other damage.
  8.  
  9. Clean the filter using compressed air.
  10.  
  11. Installation is in the reverse order of removal.
  12.  

EGR Valve

See Figures 14 and 15

  1. Tag and disconnect any hoses or pipes leading to the EGR valve.
  2.  
  3. Unbolt the EGR valve from the engine.
  4.  
  5. Remove the gasket and clean the area thoroughly.
  6.  

To install:
  1. Place a new gasket and the EGR valve into position. Tighten the mounting bolts.
  2.  
  3. Attach all hoses or pipes leading the valve.
  4.  



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Fig. Fig. 14: Exploded view of the EGR valve mounting-1974 18R-C engine



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Fig. Fig. 15: Exploded view of the EGR valve mounting-1975-77 20R engine

 
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