AMC Coupes/Sedans/Wagons 1975-1988 Repair Information

Adjustments

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Some of these adjustments procedures require that the air cleaner be kept in place. A flexible screwdriver will probably be needed to reach the carburetor screws.

4-121 ENGINES



See Figure 1

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Fig. Fig. 1: Component locations on the Holley-Weber 5210 2-bbl carburetor

The 4-cylinder engine uses a staged, two barrel carburetor. The primary barrel is smaller than the secondary barrel, and mechanical linkage progressively open the secondary barrel. Idle Speed and Mixture setting procedures are as follows:

To compensate for temperature and fuel variations, while performing idle mixture adjustments, don't idle the engine over three minutes at a time. If settings are not completed within three minutes, operate the engine at 2000 rpm for one minute. Repeat as necessary until the proper adjustments are attained.

  1. Note position of the screw head slot in the limiter cap.
  2.  
  3. Remove the limiter cap by installing a sheet metal screw in the center of the cap and turning the screw clockwise.
  4.  
  5. Reset the idle screw to its approximate original position.
  6.  
  7. Attach a tachometer. Start engine and warm to operating temperature.
  8.  
  9. A throttle stop solenoid is used to adjust curb idle. With the solenoid wire connected, turn the adjusting screw of the solenoid in or out to obtain the specified setting of 30 rpm above the specified rpm.
  10.  
  11. Disconnect the solenoid wire and adjust the solenoid off idle adjusting screw to obtain 500 rpm. Connect the solenoid wire.
  12.  
  13. Turn the mixture screw clockwise (lean) until a loss of rpm is indicated.
  14.  
  15. Turn the mixture screw counterclockwise until the highest rpm reading is obtained at the best lean idle setting.
  16.  
  17. As a final adjustment, turn the mixture screw clockwise (leaner) until the specified drop in engine rpm is obtained.
  18.  
  19. Install a replacement limiter cap on the idle mixture screw, with the tab positioned inside the slot on the carburetor body, while being careful not to move the mixture screw. Idle drop specifications for 1977-78 are 120 rpm, except for high altitude manual transmission models (75 rpm). For 1979 models they are 120 for manual transmissions and 45 for automatic transmissions.
  20.  

4-151 ENGINES



See Figure 2

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Fig. Fig. 2: Adjustment points on the Rochester 2SE carburetor

The air cleaner should be removed and associated vacuum hoses plugged, choke open, A/C compressor clutch wire disconnected (if equipped), and the deceleration valve supply hose plugged. Mixture is not adjustable.

  1. Disconnect and plug the purge hose at the charcoal canister.
  2.  
  3. If equipped with a feedback system, connect a dwell meter to the single light blue wire which is taped to the mixture control solenoid wires at the carburetors. Set the meter on the six cylinder scale.
  4.  
  5. Connect a tachometer. There is a green wire above the heater fan motor for easy tachometer connection. Start the engine and allow it to reach normal operating temperature. On feedback models, the dwell meter should be fluctuating; the oscillation should be within 10° to 15° of needle movement. If not, the feedback system is not operating correctly and must be repaired.
  6.  
  7. Set the parking brake, shift automatic transmissions to Drive; if equipped with air conditioning, turn it on. Open the throttle to extend the solenoid plunger. Set idle speed by turning the solenoid idle screw. Turn off the A/C, if equipped.
  8.  
  9. Disconnect the anti-dieseling solenoid wire. Use the curb screw to adjust idle to specifications. Connect the solenoid wire.
  10.  

1975-79 6-CYLINDER AND V8 ENGINES



See Figures 3 through 8

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Fig. Fig. 3: Carter YF carburetor adjustment points



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Fig. Fig. 4: Cross-sectional view of the six cylinder altitude compensator plug location and operation



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Fig. Fig. 5: Adjustment point locations on the left side of the Autolite/Motorcraft 2100 carburetor



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Fig. Fig. 6: Autolite/Motorcraft 4350 adjustment point locations



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Fig. Fig. 7: Location of the components on the right side of the Autolite/Motorcraft 2100 carburetor



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Fig. Fig. 8: Use a screwdriver to adjust the idle screw until the proper RPM is reached

Beginning with the 1977 models, special carburetors, incorporating an altitude compensating circuit to increase the air flow are used on cars that are sold for use at elevations above 4,000 feet. The single barrel YF-1 is manually adjusted for altitude while the two barrel 2150-2 had a automatic compensator system, controlled by an aneroid, which is sensitive to atmospheric pressures. At high altitudes, where the atmospheric pressure is lower, the aneroid expands and opens an altitude compensating valve, allowing extra air to enter the carburetor and lean our the fuel/air mixture.

The aneroid is factory calibrated and is not adjustable. With a change of altitude operation, ignition timing and carburetor adjustments must be reset on all models.

This adjustment is performed with the air cleaner installed. Do not allow the engine to idle more than three minutes at a time. If the idle/mixture adjustment is not completed by the end of three minutes, run the engine for one minute at 2,000 rpm. Return to the specified rpm and continue the adjustment.

  1. Adjust the idle screw(s) to the full rich stop(s). Note the position of the screw head slot inside the limited cap slots.
  2.  
  3. Carefully remove the idle limiter cap(s) by installing a sheet metal screw in the center of the cap and turning clockwise. Discard the old caps. Return the screws to their original positions.
  4.  
  5. Install a tachometer on the engine.
  6.  
  7. Start the engine and allow it to reach normal operating temperature.
  8.  
  9. Adjust the idle speed to 30 rpm above the specified idle speed. See the Tune-Up Specifications chart.
  10.  

On most engines the idle speed is adjusted with the throttle stop solenoid. Use the following procedure for idle speed adjustment. When setting idle speed, put the manual transmission in Neutral and the automatic transmission in Drive.

  1. With the solenoid wire connected, turn the nut on the solenoid plunger, idle speed adjusting screw, or the hex screw on the solenoid carriage in or out to obtain specified idle rpm.
  2.  
  3. Tighten the solenoid locknut, if so equipped.
  4.  
  5. Disconnect the solenoid wire and adjust curb idle speed screw to obtain 500 rpm.
  6.  
  7. Connect the solenoid wire.
  8.  

On the Carter BBD 2bbl., the curb idle and fast idle screws are side by side; it is easy to get the wrong one when setting idle speed on cars without a throttle stop solenoid. The screw for idle speed is the longer of the two.

  1. Starting from the full rich stop position, as noted in step 1, turn the mixture screw(s) clockwise (leaner) until the engine loses speed.
  2.  
  3. Turn the mixture screw(s) counterclockwise until the highest rpm reading is obtained.
  4.  

On engines with two mixture screws, turn both the screws an equal number of turns unless the engine demands otherwise.

  1. If the idle speed has changed more than 30 rpm during the mixture adjustment, reset the idle to 30 rpm above the specified idle rpm as indicated in the `Tune-Up Specifications' chart.
  2.  
  3. Turn the mixture adjustment screw(s) clockwise until the rpm drops as follows:

    1975-76 6-cyl. automatic: 25 rpm
     
    1975 6-cyl. manual: 25 rpm
     
    1976 6-cyl. manual: 50 rpm
     
    1975 6-cyl. manual w/EGR and catalytic converter: 35 rpm
     
    1976 6-cyl. manual w/EGR: 50 rpm
     
    1975-76 8-cyl. automatic: 20 rpm
     
    1975 8-cyl. manual: 40 rpm
     
    1976 8-cyl. manual: 100 rpm
     
    1977-79 6-cyl. manual: 50 rpm
     
    1977-78 6-cylinder automatic Matador: 175 rpm
     
    1977-79 6-cyl. automatic high altitude: 25 rpm
     
    1978-79 6-cyl. manual high altitude: 50 rpm
     
    1978-79 6-cyl. 2-bbl automatic: 25 rpm
     
    1977-79 6-cyl. 2-bbl manual: 50 rpm
     
    1977-78 8-cyl. automatic: 20 rpm
     
    1979 8-cyl. automatic: 40 rpm
     

  4.  
  5. Install new blue service idle limiter cap(s) over the idle mixture screw(s) with the limiter cap tang(s) positioned against the full rich stop(s). Be careful not to disturb the idle mixture setting while installing the cap(s). Press the cap(s) firmly into place.
  6.  

1980 6-CYLINDER AND V8 ENGINES



See Figure 9

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Fig. Fig. 9: Adjustment points on the BBD 2-bbl adjustments

The procedure for adjusting the Idle Speed and Mixture is called the lean drop procedure and is made with the engine operating at normal operating temperature and the air cleaner in place as follows:

  1. Turn the mixture screws to the full rich position with the tabs on the limiters against the stops. Note the position of the screw head slot inside the limiter cap slots.
  2.  
  3. Remove the idle limiter caps by threading a sheet metal screw in center of the cap and turning clockwise. Discard the limiter caps.
  4.  
  5. Reset the adjustment screws to the same position noted before the limiter caps were removed.
  6.  
  7. Start the engine and allow it to reach normal operating temperature.
  8.  
  9. Adjust the idle speed to 30 rpm above the specified rpm. See the Tune-Up Specifications chart. On 6-cylinder engines with a throttle stop solenoid, turn the solenoid in or out to obtain the specified rpm. On V8 engines with a throttle stop solenoid, turn the hex screw on the throttle stop solenoid carriage to obtain the specified rpm. This is done with the solenoid wire connected. Tighten the solenoid locknut, if so equipped. Disconnect the solenoid wire and adjust the curb idle speed screw to obtain an idle speed of 500 rpm. Reconnect the solenoid wire.
  10.  
  11. Starting from the full rich stop position, as was determined before the limiter caps were removed, turn the mixture adjusting screws clockwise (leaner) until a loss of engine speed is noticed.
  12.  
  13. Turn the screws counterclockwise (richer) until the highest rpm reading is obtained at the best lean idle setting. The best lean idle setting is on the lean side of the highest rpm setting without changing rpm.
  14.  
  15. If the idle speed changed more than 30 rpm during the mixture adjustment procedure, reset the idle speed to 30 rpm above the specified rpm with the idle speed adjusting screw or the throttle stop solenoid and repeat the mixture adjustment.
  16.  
  17. Install new limiter caps over the mixture adjusting screws with the tabs positioned against the full rich stops. Be careful not to disturb the idle mixture setting while installing the caps.
  18.  

1981-82 6-CYLINDER AND V8 ENGINES



See Figure 10

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Fig. Fig. 10: On the 197679 2150 models; remove the 2 piece plugs and caps from the idle mixture screws

Idle mixture screws on these carburetors are sealed with plugs or dowel pins. A mixture adjustment must be undertaken only when the carburetor is overhauled, the throttle body replaced, or the engine does not meet required emission standards. Since expensive testing equipment is needed to properly set the mixture, only the idle speed adjusting procedure is given below.

The adjustment is made with the manual transmission in neutral and the automatic in drive. Therefore, make certain that the vehicle's parking brake is set firmly, and that the wheels are blocked. It may be a good idea to have someone in the vehicle with their foot on the brake.

  1. Connect a tachometer, start engine and warm it to normal operating temperature. The choke and intake manifold heater (6-cylinder engine only) must be off.
  2.  
  3. If the engine speed is not within the OK range, turn the curb idle adjustment screw to obtain the specified curb idle rpm.
  4.  
  5. For the 6-cylinder engine (BBD carburetor): Disconnect the vacuum hose from the vacuum actuator and holding solenoid wire connector. Adjust the curb (slow) idle speed adjustment screw to obtain the specified curb (slow) idle rpm, if it is not within the OK range. Refer to the Emission Control Information label, and the Tune-Up Specifications Chart. Apply a direct source of vacuum to the vacuum actuator. Turn the vacuum actuator adjustment screw on the throttle lever until the specified rpm is obtained (900 rpm for manual transmissions, and 800 rpm for automatic transmissions). Disconnect the manifold vacuum source from the vacuum actuator. With the jumper wire, apply battery voltage (12v) to energize the holding solenoid. Turn the A/C ON, if equipped.
  6.  

The throttle must be opened manually to allow the Sol-Vac throttle positioner to be extended.

With the Sol-Vac throttle positioner extended, the idle speed should be 650 rpm for automatic transmission equipped vehicles and 750 rpm for manual transmission equipped vehicles. If the idle speed is not within tolerance, adjust the Sol-Vac (hex-head adjustment screw) to obtain the specified rpm. Remove the jumper wire from the Sol-Vac holding solenoid wire connector. Connect the Sol-Vac holding solenoid wire connector. Connect the original hose to the vacuum actuator.

  1. For four and eight cylinder engines, turn the nut on the solenoid plunger or the hex screw on the solenoid carriage to obtain the specified idle rpm. Tighten the locknut, if equipped. Disconnect the solenoid wire connector and adjust the curb idle screw to obtain a 500 rpm idle speed. Connect the solenoid wire connector. If the model 2150 carburetor (8-cylinder engine), is equipped with a dashpot, fully depress the dashpot stem with the throttle at the curb idle position, and measure the clearance between the stem and throttle lever. The clearance should be 0.032 in. (0.8128mm). Adjust it by loosening the locknut and turning the dashpot.
  2.  

1983 4-150 ENGINES



  1. Fully warm up the engine.
  2.  
  3. Check the choke fast idle adjustment: Disconnect and plug the EGR valve vacuum hose. Position the fast idle adjustment screw on the second step of the fast idle cam with the transmission in neutral. Adjust the fast idle speed to 2000 rpm for manual transmission and 2300 rpm for automatic transmission. Allow the throttle to return to normal curb idle and reconnect the EGR vacuum hose.
  4.  
  5. To adjust the Sol-Vac Vacuum Actuator: Remove the vacuum hose from the vacuum actuator and plug the hose. Connect an external vacuum source to the actuator and apply 10-15 in.Hg. of vacuum to the actuator. Shift the transmission to Neutral. Adjust the idle speed to the following rpm using the vacuum actuator adjustment screw on the throttle lever: 850 rpm for automatic transmission 950 rpm for manual transmission. The adjustment is made with all accessories turned OFF.
  6.  

The curb idle should always be adjusted after vacuum actuator adjustment.

  1. To adjust the curb idle: Remove the vacuum hose from the Sol-Vac vacuum actuator and plug the hose. Shift the transmission into Neutral. Adjust the curb idle using the 1 / 4 in. (6.35mm) hex-head adjustment screw on the end of the Sol-Vac unit. Set the speed to 750 rpm for manual transmission, 700 rpm for automatic transmission. Reconnect the vacuum hose to the vacuum actuator.
  2.  

Engine speed will vary 10-30 rpm during this mode due to the closed loop fuel control.

  1. To adjust the TRC (Anti-Diesel): The TRC screw is preset at the factory and should not require adjustment. However, to check adjustment, the screw should be 3 / 4 turn from closed throttle position.
  2.  

1983-84 6-258 ENGINE Sol-Vac Vacuum Actuator



  1. Disconnect and plug the vacuum hose to the Sol-Vac vacuum actuator.
  2.  
  3. Disengage the Sol-Vac electrical connector. Connect an external vacuum source to the vacuum actuator and apply 10-15 in.Hg. of vacuum.
  4.  
  5. Open throttle for at least 3.0 seconds (1200 rpm); then close throttle.
  6.  
  7. Set the speed using the vacuum actuator adjustment screw on the throttle lever to obtain specified rpm.
  8.  
  9. Disconnect the external vacuum source. Reconnect the Sol-Vac vacuum hose and electrical connector.
  10.  

Sol-Vac Holding Solenoid See Figure 11

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Fig. Fig. 11: Location of the idle speed adjustment screwMotorcraft 2100, 2150, 4300, 4300 (with TSP)

The Sol-Vac vacuum actuator adjustment should always precede the Sol-Vac solenoid adjustment.

  1. Disconnect and plug the vacuum hose at the Sol-Vac vacuum actuator.
  2.  
  3. Disengage the Sol-Vac electrical connector.
  4.  
  5. Energize the Sol-Vac holding solenoid with either of the two following methods:
    1. Apply battery voltage (12v) to the solenoid, or,
    2.  
    3. Reconnect the Sol-Vac electrical connector and turn on the rear window defogger or turn on the air conditioner with the compressor disconnected.
    4.  

  6.  
  7. Open throttle for at least 3.0 seconds (1,200 rpm) to allow the Sol-Vac holding solenoid to fully extend.
  8.  
  9. Set the speed using the 1 / 4 in. (6.35mm) hex-head adjustment screw on the end of the Sol-Vac unit to obtain the specified rpm.
  10.  
  11. Reopen the throttle above 1,200 rpm to insure the correct holding position and reset the speed if necessary. Reconnect the vacuum hose to the Sol-Vac actuator. Reconnect the Sol-Vac electrical connector if disconnected.
  12.  

1985-86 Models

The carburetor choke and intake manifold heater must be OFF. This occurs when the engine coolant heats to approximately +160°F (71°C).

  1. Have the engine at normal operating temperature. Connect a tachometer to the ignition coil negative (TACH) terminal.
  2.  
  3. Remove the vacuum hose from the Sol-Vac vacuum actuator unit. Plug the vacuum hose. Disengage the holding solenoid wire connector.
  4.  
  5. Adjust the curb (slow) idle speed screw to obtain the correct curb idle speed. Refer to the specifications under Idle Speed or refer to the Emission Information label, under the hood, for the correct curb idle engine rpm.
  6.  
  7. Apply a direct source of vacuum to the vacuum actuator, using a hand vacuum pump or its equivalent. When the Sol-Vac throttle positioner is fully extended, turn the vacuum actuator adjustment screw on the throttler lever until the specified engine rpm is obtained. Disconnect the vacuum source from the vacuum actuator.
  8.  
  9. With a jumper wire, apply battery voltage (12v) to energize the holding solenoid.
  10.  

The holding wire connector can be installed and either the rear window defroster or the air conditioner (with the compressor clutch wire disconnected) can be turned on to energize the holding solenoid.

  1. Hold the throttle open manually to allow the throttle positioner to fully extend.
  2.  

Without the vacuum actuator, the throttle must be opened manually to allow the Sol-Vac throttle positioner to fully extend.

  1. If the holding solenoid idle speed is not within specifications, adjust the idle using the 1 / 4 in. (6.35mm) hex-headed adjustment screw on the end of the Sol-Vac unit. Adjust to specifications.
  2.  
  3. Disconnect the jumper wire from the Sol-Vac holding solenoid wire connector, if used. Connect the wire connector to the Sol-Vac unit, if not connected. Install the original vacuum hose to the vacuum actuator.
  4.  
  5. Remove the tachometer and if disconnected, connect the compressor clutch wire. Install any other component that was previously removed.
  6.  

See Figures 12, 13 and 14

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Fig. Fig. 12: Troubleshooting Engine Performance



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Fig. Fig. 13: Troubleshooting Engine Performance (Cont.)



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Fig. Fig. 14: Troubleshooting Engine Performance (Cont.)

 
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