Exhaust Gas Recirculation: Service and Repair

BACK PRESSURE TRANSDUCER VALVE, REPLACE

1. Disconnect vacuum hoses from valve.
2. Remove attaching bolts from clamp bracket, then transducer.
3. Reverse procedure to install.

EGR VALVE, REPLACE

1. Disconnect EGR vacuum hose from valve.
2. Remove bolts or nuts securing EGR valve to manifold.
3. Remove EGR valve from manifold.
4. Reverse procedure to install.

EGR-TVS/EGR-TVV, REPLACE

1. Drain engine coolant.
2. Disconnect vacuum hoses and remove switch.
3. Reverse procedure to install switch. When installing switch, apply a suitable sealer to the switch threads. Torque switch to 20 ft lbs.

INTAKE MANIFOLD EGR PASSAGES
When cleaning intake manifold EGR passages, care should be taken to ensure that all loose particles are completely removed to prevent them from clogging the EGR valve or from being ingested into the engine.
1. Remove carburetor.
2. Disconnect vacuum hose from EGR valve, then remove EGR valve to manifold retaining bolts and valve.
3. Remove deposits from EGR ports by hand using a suitable drill bit and screwdriver.
4. Brush small deposits down EGR port into passages, then using compressed air, blow ports clean. Solvents should not be used to clean EGR valve or passages, since damage to system may result.
5. Install EGR valve, using new gasket.
6. Install carburetor.

Fig. 44 Vacuum servo EFE diagnosis chart:

EGR VALVE CLEANING
Some General Motors EGR valves have a removable pintle and seat, while others are non-serviceable. Serviceable valves can be identified by punch marks located on valve seat and base, Fig. 44.



NON-SERVICEABLE TYPE

1. Remove EGR valve from vehicle.
2. Holding valve assembly in hand, tap on round pintle with plastic hammer to remove deposits from valve seat. Empty loose particles from valve.
3. Clean mounting base and pintle using a wire brush, then depress valve diaphragm and check seating area for cleanliness. If pintle or seat are not completely clean, repeat Step 2.
4. Inspect valve outlet and remove deposits with suitable sharp tool.
5. Clean intake manifold to EGR valve mounting surface with wire brush, then install EGR valve assembly using new gasket.

Fig. 58 Serviceable EGR valve:

SERVICEABLE TYPE

1. Remove EGR valve from vehicle.
2. Clean seat and base, then inspect for alignment marks located on base and seat. These marks must align and alignment be retained during reassembly.
3. Measure distance from base surface to seal shoulder. Record the measurement to aid in reassembly, Fig. 58.
4. Secure EGR valve in bench vise, then remove seat from pintle using suitable wrench. If pintle seat is difficult to remove, rock fore and aft to overcome tightness due to factory staking.
5. Holding valve in upright position:
a. Remove pintle by pulling downward with pliers, making sure jaws are not located on sealing surface.
b. Using drill bit slightly smaller than shaft inside diameter, turn bit clockwise up into shaft for approximately one inch, then pull out without turning.
c. Tap shaft lightly to loosen debris from shaft inner surface.
6. Clean holes in pintle with suitable drill bit, then brush and air blow pintle and shaft to complete cleaning. Safety glasses should be worn to protect eyes from flying debris.
7. Position pintle over end of shaft and press down until pintle lock ring feels seated, then proceed as follows:
a. Screw seat into base until distance between base and seal shoulder is the same as recorded in Step 3.
b. Position scribe marks on base and seat so that they are in alignment.
8. Supporting valve at base, re-stake seat at original staking locations.
9. Install EGR valve using new gasket.