Jeep Wagoneer/Commando/Cherokee 1984-1998

Idle Speed and Mixture Adjustments

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This section contains only tune-up adjustment procedures for fuel systems. Descriptions, adjustments, and replacement procedures for fuel system components can be found in Section 5.

1984-85 MODELS



2.5L Engine
  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 2,000 rpm for manual transmission models, or 2,300 rpm for automatic transmission models. Allow the throttle to return to normal curb idle and reconnect the EGR vacuum.
  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 (68-103 kPa) 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 models, or 950 rpm for manual transmission models. 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. hex head adjustment screw on the end of the Sol-Vac unit. Set the speed to 750 rpm for manual transmission models, or 700 rpm for automatic transmission models. 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: 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 the closed throttle position.
  2.  

2.8L Engine
EXCEPT CALIFORNIA
  1. Connect a tachometer to the ignition coil negative terminal or to the pigtail wire connector above the heater blower motor.
  2.  
  3. Disconnect and plug the vacuum hose at the distributor vacuum advance.
  4.  
  5. If necessary, adjust the ignition timing with the engine speed at or below specifications.
  6.  
  7. Unplug and reconnect the vacuum hose to the distributor vacuum advance unit.
  8.  
  9. Disconnect the deceleration valve hose and canister purge hose. Plug the hose and remove the air cleaner assembly.
  10.  
  11. If equipped with air conditioning, turn the control switch to the ON position and open the throttle momentarily to insure the solenoid armature is fully extended. Adjust the solenoid idle speed adjusting screw to obtain the specified engine curb idle speed rpm. Turn the air conditioning control switch to the OFF position.
  12.  
  13. If not equipped with air conditioning, adjust the engine idle speed rpm with the solenoid idle speed adjusting screw. Disconnect the solenoid wire and adjust the curb idle.
  14.  
  15. Install the air cleaner assembly. Connect all hoses and other connections.
  16.  

CALIFORNIA MODELS

See Figures 1 and 2

Some California Jeeps with the V6 engine are equipped with a 2,200 hour engine timer. The timer activates a solenoid to control operation of the carburetor secondary vacuum break after 2,200 hours of vehicle operation. The timer is not a serviceable component and must not be disassembled. In the event of a timer malfunction, the complete engine wiring harness must be replaced.

  1. Connect a tachometer to the ignition system. Start the engine and operate to normal operating temperature.
  2.  



Click image to see an enlarged view

Fig. Fig. 1: E2SE carburetor idle speed adjustment-without A/C

  1. Turn off all accessories including the air conditioning system.
  2.  
  3. Put the manual transmission equipped vehicles in Neutral, and the automatic transmission equipped vehicles in Drive with the parking brake locked and the wheels chocked.
  4.  
  5. Adjust the curb idle speed adjusting screw to obtain the specified rpm of 700 for both manual and automatic transmission equipped vehicles.
  6.  
  7. Disconnect the vacuum hose from the idle kick actuator and connect an outside vacuum source to the actuator. Apply 15 in. Hg. (51 kPa) of vacuum to the actuator.
  8.  
  9. Adjust the actuator hex head adjustment screw for the specified 1,200 rpm with both types of transmissions in the Neutral position.
  10.  
  11. Stop the engine, remove the tachometer and vacuum pump. Install the vacuum hose to the actuator.
  12.  



Click image to see an enlarged view

Fig. Fig. 2: E2SE carburetor idle speed adjustment-with A/C

1985-87 MODELS



2.1L Diesel Engine

See Figure 3

  1. Connect a tachometer to the ignition system. The idle speed is adjusted on the injection pump linkage.
  2.  
  3. Loosen the screw locknut, adjust the idle speed to 750-850 rpm with the adjusting screw and tighten the locknut.
  4.  
  5. Stop the engine and remove the tachometer.
  6.  



Click image to see an enlarged view

Fig. Fig. 3: The arrow indicates the idle speed adjusting screw

2.5L Engine
WITH YFA CARBURETOR
  1. The Throttlle Return Control TRC (anti-diesel) adjustment screw is statically set at 3 / 4 turn from the throttle valve closed position during factory assembly and does not normally require readjustment. Should this adjustment be required, turn the adjustment screw counterclockwise to the throttle plate closed position and then turn the screw clockwise 3 / 4 turn.
  2.  
  3. Connect a tachometer to the ignition coil TACH wire connector.
  4.  
  5. Place the transmission in Neutral and set the parking brake.
  6.  
  7. Start the engine and allow it to reach normal operating temperature.
  8.  
  9. Connect an external vacuum source to the Sol-Vac vacuum actuator and apply 10-15 in. Hg (34-51 kPa) of vacuum. Plug the engine vacuum hose.
  10.  
  11. Adjust the vacuum actuator until an engine speed of approximately 1,000 rpm is achieved.
  12.  

Refer to the Vehicle Emission Control Information Label for the latest specifications for the particular engine being adjusted.

  1. Remove the vacuum source from the vacuum actuator and retain the plug in the vacuum hose from the engine.
  2.  
  3. Turn the hex-head curb idle speed adjustment screw until the speed of 500 rpm is obtained.
  4.  

Refer to the Vehicle Emission Control Label for the latest specifications for the particular engine being adjusted.

  1. Stop the engine, then unplug and connect the engine vacuum hose to the vacuum actuator.
  2.  
  3. Remove the tachometer from the engine.
  4.  

WITH THROTTLE BODY FUEL INJECTION

Adjustments are not possible on this unit, as all functions are computer controlled.

2.8L Engines
EXCEPT CALIFORNIA
  1. Connect a tachometer to the ignition coil negative terminal or to the pigtail wire connector above the heater blower motor.
  2.  
  3. Disconnect and plug the vacuum hose at the distributor vacuum advance.
  4.  
  5. If necessary, adjust the ignition timing with the engine speed at or below specifications.
  6.  
  7. Unplug and reconnect the vacuum hose to the distributor vacuum advance unit.
  8.  
  9. Disconnect the deceleration valve hose and canister purge hose. Plug the hose and remove the air cleaner assembly.
  10.  
  11. If equipped with air conditioning, turn the control switch to the ON position and open the throttle momentarily to insure the solenoid armature is fully extended. Adjust the solenoid idle speed adjusting screw to obtain the specified engine curb idle speed rpm. Turn the air conditioning control switch to the OFF position.
  12.  
  13. If not equipped with air conditioning, adjust the engine idle speed rpm with the solenoid idle speed adjusting screw. Disconnect the solenoid wire and adjust the curb idle.
  14.  
  15. Install the air cleaner assembly. Connect all hoses and other connections.
  16.  

CALIFORNIA MODELS

Some California Jeeps with the V6 engine are equipped with a 2,200 hour engine timer. The timer activates a solenoid to control operation of the carburetor secondary vacuum break after 2,200 hours of vehicle operation. The timer is not a serviceable component and must not be disassembled. In the event of a timer malfunction, the complete engine wiring harness must be replaced.

  1. Connect a tachometer to the ignition system. Start the engine and operate to normal operating temperature.
  2.  
  3. Turn off all accessories including the air conditioning system.
  4.  
  5. Put the manual transmission equipped vehicles in Neutral and the automatic transmission equipped vehicles in Drive with the parking brake set and the wheels chocked.
  6.  
  7. Adjust the curb idle speed adjusting screw to obtain the specified rpm of 700 for both manual and automatic transmission equipped vehicles.
  8.  
  9. Disconnect the vacuum hose from the idle kick actuator and connect an outside vacuum source to the actuator. Apply 15 in. Hg (68 kPa) of vacuum to the actuator.
  10.  
  11. Adjust the actuator hex head adjustment screw for the specified 1,200 rpm with both types of transmissions in the Neutral position.
  12.  
  13. Stop the engine, remove the tachometer and vacuum pump. Install the vacuum hose to the actuator.
  14.  

1988-98 MODELS



The 2.5L TBI, 2.5L MFI, 4.0L MFI, 5.2L MFI and 5.9L MFI are all fuel injected. Routine adjustments are computer controlled. No routine idle speed adjustments are possible.

 
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