Idle Speed: Adjustments

CURB IDLE SPEED CHECK

NOTE: Curb idle speed is controlled by the EEC-IV processor and the idle speed control device. If the control system is operating properly, these speeds are fixed and cannot be changed using traditional adjustment techniques.

1. Set parking brake and block wheels. Disconnect and plug vacuum line to automatic parking brake release (if equipped).
2. Connect a tachometer to the engine.
3. START the engine and bring to normal operating temperature. Check engine for vacuum leaks.
4. Turn all accessories OFF.
5. After the engine has been idling for 2 minutes, check the idle speed in DRIVE (A/T) or NEUTRAL (M/T). Placing the transmission in PARK should increase the idle approximately 100 rpm.
6. Lightly accelerate and decelerate. Engine rpm should return to specifications.
NOTE: It may take up to 2 minutes or the idle speed to re-learn.
7. Reconnect the automatic parking brake release vacuum line (if disconnected).

MINIMUM ISC LIMIT ADJUSTMENT

NOTE: If the curb idle is above specifications, verify that the throttle linkage is free, that travel is not obstructed, and that the cruise control linkage (if equipped) is not holding the throttle open. If while the engine is running it is found that the throttle lever is not in contact with the ISC motor and being held open by the throttle stop adjusting screw, the screw must be adjusted. To adjust the throttle stop adjusting screw the ISC motor must be fully retracted. To accomplish this, the following procedure must be followed exactly.

1. With the engine OFF, remove the air cleaner.

Jumper Wire Installed Between Pin #2 And Self Test Input (STI):

2. Connect a jumper wire between the self-test input (STI) connector and the signal return pin on the self-test connector.
3. Turn the ignition ON, but DO NOT START the engine.
4. The ISC plunger should fully retract in about 15 seconds. If it does not, perform quick test.
5. Turn the key OFF and wait for 15 seconds.
6. Remove the jumper wire from the self test connector and unplug the ISC motor from the harness.

Throttle Stop Adjusting Screw:

7. Perform the throttle stop adjustments as follows:
a. Remove the CFI assembly from the vehicle.
b. Using an ice pick or small punch, remove the aluminum adjusting screw cover from the CFI assembly.
c. Remove and replace the adjusting screw.
8. Install the CFI assembly on the vehicle.
9. START the engine and allow idle speed to stabilize, then set the idle rpm to decal specification by turning the throttle stop adjusting screw.
10. Reconnect the ISC motor harness.