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Maverick and Comet Repair

Emission Controls

EXHAUST GAS RECIRCULATION SYSTEM
System Test

  1. Allow the engine to warm up, so that the coolant temperature has reached at least 125°F.
  2. Disconnect the vacuum hose which runs from the temperature cut-in valve to the EGR valve at the EGR valve end. Connect a vacuum gauge to this hose with a T-fitting.
  3. Increase engine speed. The gauge should indicate a vacuum. If no vacuum is present, check the following:
    a. The carburetor—look for a clogged vacuum port.
    b. The vacuum hoses—including the vacuum hoses to the transmission modulator.
    c. The temperature cut-in valve—if no vacuum is present at its outlet with the engine temperature above 125°F and vacuum available from the carburetor, the valve is defective.
  4. If all of the above tests are positive, check the EGR valve itself.
  5. Connect an outside vacuum source and a vacuum gauge to the valve.
  6.  Apply vacuum to the EGR valve. The valve should open at 3-10 in. Hg, the engine idle speed should slow down, and the idle quality should become more rough.
  7. If this does not happen, i.e., the EGR valve remains closed, the EGR valve is defective and must be replaced.
  8. If the valve stem moves but the idle remains the same, the valve orifice is clogged and must be cleaned.
    NOTE: If an outside vacuum source is not available, disconnect the hose which runs between the EGR valve and the temperature cut-in valve and plug the hose connections on the cut-in valve. Connect the EGR valve hose to a source of intake manifold vacuum and watch the idle. The results should be the same as in steps 6—7, above.

Temperature Cut-In Valve (EGR Ported Vacuum Switch)
VALVE BENCH TEST

  1. Remove the valve from the engine.
  2. Connect an outside source of vacuum to the top port on the valve. Leave the bottom port vented to the atmosphere.
  3. Use ice or an aerosol spray to cool the valve below GOT.
  4. Apply 20 in. Hg vacuum to the valve. The valve should hold a minimum of 19 in. Hg vacuum for 5 minutes without leaking down.
  5. Leave die vacuum source connected to the valve and place it, along with a high temperature thermometer, into a non-metallic, heat resistant container full of water.
  6. Heat the water. The vacuum in the valve should drop to zero once the temperature of the water reaches about 125°F.
  7.  Replace the valve if it fails either of the tests.

Vacuum Modulator Test
NOTE: The vacuum modulator is used only with an automatic transmission.

  1. Remove the vacuum modulator from the car.
  2. Connect the modulator to an outside vacuum source: a distributor tester, for example:
    NOTE: The vacuum source should be adjusted to supply 18 in. Hg, with the end of the vacuum line blocked off.
  3. Connect the vacuum line from the vacuum source to the EGR port on the vacuum modulator.
  4. The vacuum modulator should hold the 18 in. Hg reading. If it does not, then the diaphragm is leaking and must be replaced.

EGR VENTURI VACUUM AMPLIFIER SYSTEM
System Test
The amplifiers have built-in calibrations, and no external adjustments are required. If the amplifier tests reveal it is malfunctioning, replace die amplifier. All connections are located on one side of the amplifier. A vacuum connector and hose assembly is used to assure that proper connections are made at die amplifier. The amplifier is retained with a sheet-metal screw.

  1. Operate the engine until normal operating temperatures are reached.
  2. Before the vacuum amplifier is checked, inspect all other basic components of the EGR System (EGR valve, EGR/PVS valve, hoses, routing, etc.).
  3.  Check vacuum amplifier connections for proper routing and installation. If necessary, refer to the typical vacuum amplifier schematic.
  4. Remove hose at EGR valve.
  5. Connect vacuum gauge to EGR hose. Gauge must read in increments of at least 1 in. Hg graduation.
  6. Remove hose at carburetor venturi (leave off).
  7. With engine at curb idle speed, vacuum gauge reading should be within ±0.3 in. Hg of specified bias value as shown in amplifier specifications for other than zero bias. Zero bias may read from 9 to 0.5 in. Hg. If out of specification, replace amplifier.
  8. Depress accelerator and release after engine has reached 1500 to 2000 rpm. After engine has returned to idle, the vacuum must return to bias noted in Step 7. If bias has changed, replace amplifier. Also, if vacuum shows a marked increase (greater than 1 in. Hg) during acceleration period, the amplifier should be replaced.
  9. Hook up venturi hose at carburetor with engine at curb idle rpm. If a sizeable increase in output vacuum is observed, (more than 0.5 in. Hg above Step 7), check idle speed. High idle speed could increase output vacuum due to venturi vacuum increase. See engine decal for correct idle specifications.
  10. Check amplifier reservoir and connections as follows: Disconnect external reservoir hose at amplifier and cap or plug. Depress accelerator rapidly to 1500 to 2000 rpm. The vacuum should increase to 4 in. Hg or more. If out of specifications, replace amplifier.

TEMPERATURE ACTIVATED VACUUM SYSTEM
System Test

  1. Disconnect the vacuum line from the primary port of the distributor. Connect a vacuum gauge to the line by means of a T-fitting. Connect the other end of the T-fitting to the distributor.
  2. Be sure that the air temperature is above 65°F. Hot water may be used to warm the temperature switch, which is located in the front door pillar.
  3. Place the transmission in Park or Neutral. Start the engine.
  4. Run the engine at idle; the vacuum gauge should read zero.
  5. Increase the engine speed to 1,500 rpm or slightly more. The gauge should read 5 in. Hg or better.
  6. If there is no vacuum reading, check for leaking, plugged, or pinched lines and fittings.
  7. Detach the EGR port hose and plug up the carburetor line. The vacuum gauge should read zero.
  8. If it does not, check the lines and then proceed with the 3-way vacuum valve test, below. If it does, go on to Step 9.
  9. Next, detach one of the power leads from the 3-way vacuum valve.
  10. Speed the engine up to 1,500 rpm or more. The vacuum gauge should now read 6 in. Hg or better.
  11. If the system fails to function as outlined, check the ambient temperature switch, the EGR valve, or the 3-way vacuum valve.
  12. If everything is functioning properly, reconnect the leads and vacuum lines after disconnecting the vacuum gauge.

Temperature Switch Test
See "Electronic Spark Control Component Tests—Temperature Sensor."

3-Way Solenoid Valve Test

  1. Remove the 3-way vacuum valve from the car.
  2. Connect a vacuum gauge to the horizontal part at the bottom of the valve.
  3. Apply a vacuum source to the horizontal port at the top of the valve.
  4. Ground one of the valve terminals while connecting the other terminal to a 12V power supply. The vacuum gauge should read zero.

Thermactor System
Before performing any extensive diagnosis of the emission control systems, verify that all specifications on the Certification Label are met, because the following systems or components may cause symptoms that appear to be emission related.

Fabricating A Test Gauge Adapter
In order to test the 3 major components of a Thermactor system (air pump, check valve and by-pass valve), a pressure gauge and adapter are required. The adapter can be fabricated as follows:

  1. Obtain these items:
    a.) 1/2-inch pipe tee
    b.) 1/2-inch pipe, 2-inches long and threaded at one end
    c.) 1/2-inch pipe plug
    d.) 1/2-inch reducer bushing or other suitable gauge adapter
  2. Apply sealer to threaded ends of pipe, plug and bushing. Assemble as shown in the illustration.
  3. Drill 11/32 inch (0.3437) diameter hole through center of pipe plug. Clean out chips after drilling.
  4. Attach pressure gauge with 1/4-psi increments to bushing or adapter.

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Air Pump Tests
CAUTION: Do not hammer on, pry, or bend the pump housing while tightening the drive belt or testing the pump.

BELT TENSION AND AIR LEAKS

  1. Before proceeding with the tests, check the pump drive belt tension to see if it is within specifications.
  2. Turn the pump by hand. If it has seized, the belt will slip, producing noise. Disregard any chirping, squealing, or rolling sounds from inside the pump; these are normal when it is turned by hand.
  3. Check the hoses and connections for leaks. Hissing or a blast of air is indicative of a leak. Soapy water, applied lightly around the area in question, is a good method for detecting leaks.

AIR OUTPUT TEST

  1. Disconnect the air supply hose at the anti-backfire valve.
  2. Connect a vacuum gauge, using a suitable adaptor, to the air supply hose.
    NOTE: If there are two hoses plug the second one up.
  3. With the engine at normal operating temperature, increase the idle speed and watch the vacuum gauge.
  4. The air flow from the pump should be steady and fall between 2-6 psi. If it is unsteady or falls below this, the pump is defective and must be replaced.

PUMP NOISE DIAGNOSIS
The air pump is normally noisy; as engine sped increases, the noise of the pump will rise in pitch. The rolling sound the pump bearings make is normal, however if this sound becomes objectionable at certain speeds, the pump is defective and will have to be replaced.

A continual hissing sound from the air pump pressure relief valve at idle, indicates a defective valve. Replace the relief valve.
If the pump rear bearing fails, a continual knocking sound will be heard. Since the rear bearing is not separately replaceable, the pump will have to be replaced as an assembly.

Check Valve Test

  1. Before starting the test, check all of the hoses and connections for leaks.
  2. Detach the air supply hose(s) from the check valve(s).
  3. Insert a suitable probe into the check valve and depress the plate. Release it; the plate should return to its original position against the valve seat. If binding is evident, replace the valve.
  4. Repeat Step 3 if two valves are used.
  5. With the engine running at normal operating temperature, gradually increase its speed to 1,500 rpm. Check for exhaust gas leakage. If any is present, replace the valve assembly.
    NOTE: Vibration and flutter of the check valve at idle speed is a normal condition and does not mean that the valve should be replaced.

Air By-Pass Valve Test

  1. Detach the hose, which runs from the by-pass valve to the check valve, at the bypass valve hose connection.
  2. Connect a tachometer to the engine. With the engine running at normal idle speed, check to see that air is flowing from the by-pass valve hose connection.
  3. Speed the engine up, so that it is running at 1,500-2,000 rpm. Allow the throttle to snap shut. The flow of air from the by-pass valve at the check valve hose connection should stop momentarily and air should then flow from the exhaust port on the valve body or the silencer assembly.
  4. Repeat Step 3 several times. If the flow of air is not diverted into the atmosphere from the valve exhaust port or if it fails to stop flowing from the hose connection, check the vacuum lines and connections. If these are tight, the valve is defective and requires replacement.
  5. A leaking diaphragm will cause the air to flow out both the hose connection and the exhaust port at the same time. If this happens, replace the valve.

Component Replacement
PVC VALVE
Disconnect the ventilation hose at the oil filler cap on V8 applications and pull out the PCV valve from its grommet. On six-cylinder engines, disconnect the ventilation hose from its connection at the front of the valve cover and pull out the PCV valve from its grom­met. Clean out all of the passageways in the hoses and fittings with a kerosene soaked rag. Install a new PCV valve in its grommet and connect the ventilation hose.

EVAPORATIVE CONTROL CHARCOAL CANISTER
Loosen and remove the canister mounting bolts from the mounting bracket. Disconnect the purge hose from the air cleaner and the feed hose from the fuel tank. Discard the old canister and install a new unit. Make sure that the hoses are connected properly.

PORTED VACUUM SWITCH (DISTRIBUTOR VACUUM CONTROL VALVE)

  1. Drain about one gallon of coolant out of the radiator.
  2. Tag the vacuum hoses that attach to the control valve and disconnect them.
  3. Unscrew and remove the control valve.
  4. Install the new control valve.
  5. Connect the vacuum hoses.
  6. Fill the cooling system.

HEATED AIR INTAKE SYSTEM
Temperature Operated Duct And Valve Assembly

  1. Remove the hex-head cap screws that secure the air intake duct and valve assembly to the air cleaner.
  2. Remove the air intake duct and valve assembly from the engine.
  3. If the duct and valve assembly was removed because of a suspected temperature malfunction, check the operation of the thermostat and valve plate assembly. Refer to the Air Intake Duct test for the proper procedure.
  4. If inspection reveals that the valve plate is sticking or the thermostat is malfunctioning, remove the thermostat and valve plate
    as follows: Detach the valve plate tension spring from the valve plate using long nose pliers. Loosen the thermostat locknut and un­screw the thermostat from the mounting bracket. Grasp the valve plate and with­draw it from the duct.
  5. Install the air intake duct and valve assembly on the shroud tube.
  6. Connect the air intake duct and valve assembly to the air cleaner and tighten the 2 hex-head retaining cap screws.
  7. If it was necessary to disassemble the thermostat and air duct and valve, assemble the unit as follows:
     a.) Install  the valve plate.   Install  the locknut on the thermostat, and screw the thermostat into the mounting bracket. Install the valve plate tension spring on the valve plate and duct.
    b.)  Check the operation of the thermostat and air duct assembly. Refer to the Air Intake Duct Test for the proper procedure. Tighten the locknut.
    8. Install the vacuum override motor (if applicable) and check for proper operation.

Vacuum Operated Duct And Valve Assembly

  1. Disconnect the vacuum hose at the vacuum motor.
  2. Remove the hex head cap screws that secure the air intake duct and valve assembly to the air cleaner.
  3. Remove the duct and valve assembly from the engine.
  4. Position the duct and valve assembly to die air cleaner and heat stove tube. Install the attaching cap screws.
  5. 5.Connect the vacuum line at the vacuum motor.