Component Tests and General Diagnostics
Fig. 6 Control System Component Identification 1985:
Fig. 7 Control System Component Identification 1986 on:
CARBURETOR FEEDBACK SYSTEM
1. Ensure that coolant temperature is less than 45° F.
2. Disconnect vacuum hose from vacuum switch (switch B on 1985 models), Figs. 6 and 7, then start engine and check for vacuum at disconnected hose.
3. No vacuum should be present at hose. If vacuum is present check for defective thermal vacuum switching valve.
4. Reconnect vacuum hose and run engine until it reaches normal operating temperature.
5. Disconnect electrical connector to EBCV and hold engine speed at steady 2500 RPM.
6. Reconnect electrical connector. Engine speed should momentarily drop approximately 300 RPM.
7. Return engine to idle, then disconnect and connect EBCV connector. Engine speed should not change.
8. Disconnect vacuum hose from vacuum switch (switch B on 1985 models), Figs. 6 and 7, and repeat steps 5 through 7. Engine speed should not change as EBCV connector is connected and disconnected.
9. If results are not as outlined in steps 6 through 8 test vacuum switch.
Fig. 1 Mixture Control System Wiring Schematic:
Fig. 2 Carburetor Feedback System Operation:
10. Refer to chart in Fig. 2, and ensure system operates as outlined.
11. If operation is not as outlined, check electrical connections and wiring, Fig. 1, inspect vacuum hoses, and test components individually.
Fig. 1 Mixture Control System Wiring Schematic:
Fig. 3 Deceleration Fuel Cut Operation. 1985:
Fig. 4 Deceleration Fuel Cut Operation. 1986-1987:
Fig. 6 Control System Component Identification 1985:
Fig. 7 Control System Component Identification 1986 on:
DECELERATION FUEL CUT
Ensure that idle mixture is properly adjusted prior to testing the deceleration fuel cut system.
1. Connect tachometer following manufacturer's instructions.
2. Start engine and ensure that engine runs properly at idle.
3. If engine fails to idle properly, check for sticking first fuel cut solenoid.
4. Disconnect electrical connector to vacuum switch A on 1985 models or throttle position switch on 1986 and later models, Figs. 6 and 7.
5. Gradually increase engine speed to 2300 RPM.
6. Engine should fluctuate or ``hunt'' with throttle held steady.
7. Reconnect electrical connector to vacuum or throttle position switch and repeat step 5.
8. Engine should run normally.
9. If engine fails to perform as outlined, check system operation as shown in Figs. 3 and 4.
10. If system fails to operate as shown, check wiring and connections, Fig. 1, inspect vacuum hoses, and test components individually. If all other components are satisfactory, check for defective ECM.
Fig. 1 Mixture Control System Wiring Schematic:
COLD MIXTURE HEATER
1. Ensure that coolant temperature is below 109° F.
2. Start engine and check for voltage at heating element white/red connector terminal, leaving connector in place.
3. If meter fails to indicate voltage, check for defective relay, damaged wiring, Fig. 1, or defective ECM.
4. Run engine until it reaches normal operating temperature, leaving meter probe connected to heating element.
5. If meter indicates voltage with coolant temperature above 109° F, check for defective thermo switch, relay or ECM.
Fig. 6 Control System Component Identification 1985:
Fig. 7 Control System Component Identification 1986 on:
COMPONENT TESTING
Electronic Air Bleed Control Valve (EBCV)
1. Disconnect electrical connector from control valve, Figs. 6 and 7.
2. Connect ohmmeter between valve positive terminal (terminal closest to lock tab) and valve body.
3. Meter should indicate no continuity.
4. Connect ohmmeter between valve terminals.
5. Valve solenoid resistance should be 11-13 ohms.
Fig. 8 Oxygen Sensor Test Connections:
Oxygen Sensor
1. Run engine until it reaches normal operating temperature.
2. Connect voltmeter to green service connector located behind right strut tower, observing polarity indicated in Fig. 8.
3. Set engine to run engine at 2500 RPM.
4. Observe voltmeter after approximately 90 seconds.
5. Meter reading should fluctuate between 0 and 6 volts at least 8 times within 10 seconds.
6. If reading is as indicated, oxygen sensor circuit is satisfactory.
7. If voltage reading is not as indicated, inspect wiring and other system components.
8. If all other components are satisfactory but oxygen sensor voltage is not as indicated, replace sensor.
First Fuel Cut Solenoid
1. Disconnect electrical connector and remove solenoid from carburetor.
2. Connect solenoid to suitable 12v power source and observe operation.
3. Audible click should be heard as solenoid is energized and de-energized.
Fig. 9 Cold Mixture Heater (CMH) Relay Test Connections:
CMH Relay
1. Disconnect electrical connector from relay and connect ohmmeter between relay terminals 1 and 2, Fig. 9.
2. Meter should indicate continuity.
3. Connect ohmmeter between relay terminals 3 and 4, Fig. 9.
4. Meter should indicate no continuity.
5. Leaving ohmmeter connected between terminals 3 and 4, connect battery voltage to relay terminal 2 and ground terminal 1.
6. Meter should indicate continuity.
Fig. 6 Control System Component Identification 1985:
Fig. 7 Control System Component Identification 1986 on:
Thermo Switch
1. Drain cooling system and remove switch from intake manifold. The thermo switch is located behind the TVSV, Figs. 6 and 7.
2. Check continuity between switch electrical connector and switch body.
3. With switch temperature below 109° F meter should indicate continuity; with temperature above 109° F meter should indicate no continuity.
4. If switch fails to perform as outlined, switch should be replaced.
Thermostatic Vacuum Switching Valve (TVSV)
1. Drain cooling system and remove switching valve from manifold, Figs. 6 and 7.
2. Immerse valve sensing element in temperature controlled solution.
Fig. 10 TVSV Port Identification:
3. Switching valve should perform as follows:
a. With temperature below 45° F air applied to port J should flow from ports L and M, and air applied to port K should flow from port N, Fig. 10.
b. With temperature between 63° and 122° F air applied to port K should flow from ports L and N, and air applied to port J should flow from port M, Fig. 10.
c. With temperature above 154° F air applied to port k should flow from ports L and N only, Fig. 10.
4. If valve fails to perform as outlined, valve should be replaced.
Fig. 6 Control System Component Identification 1985:
Fig. 7 Control System Component Identification 1986 on:
Vacuum Switches
1. Ensure engine is cold and disconnect electrical connectors from vacuum switch(s), Figs. 6 and 7.
2. Check continuity between each switch terminal and switch body.
3. On 1985 models, meter should indicate continuity for switch A and no continuity for switch B. On 1986 and later models, meter should indicate no continuity.
4. Start engine, run until it reaches normal operating temperature, then repeat step 2.
5. On 1985 models meter should indicate no continuity for switch A and continuity for switch B. On 1986 and later models, meter should indicate continuity.
Fig. 7 Control System Component Identification 1986 on:
Throttle Position Switch
1. Connect tachometer following manufacturer's instructions, start engine and run until it reaches normal operating temperature.
2. Disconnect electrical connector from throttle position switch, Fig. 7.
3. Connect ohmmeter between throttle position switch connector terminal and ground. Meter should indicate no continuity with throttle closed.
4. Slowly increase engine speed while observing ohmmeter. Meter should indicate continuity when engine speed reaches 1600-2000 RPM
5. If switch fails to perform as outlined, adjust switch with screw on actuating link and repeat check. Cooling fan must be off when adjusting throttle position switch.
6. If switch fails to perform as outlined, switch is defective.