Idle Speed: Adjustments

Instructions:

NOTE: This procedure is to be performed only if the Curb Idle is NOT within the Decal specification, with A/C OFF.





NOTE: Curb idle speed or Revolutions Per Minute (RPM) is controlled by the Electronic Engine Controller (EEC-IV) processor and the Idle Speed Control Air Bypass (ISC-BPA) valve assembly. If engine Curb Idle RPM is NOT within specification after performing this procedure, it will be necessary to perform the appropriate Electronic Fuel Injection (EFI) EEC-IV diagnostics.

1. Place the transmission in NEUTRAL, apply parking brake, and turn the A/C-Heat selector to the OFF position.
2. Bring the engine to normal operating temperature and turn OFF.
3. DISCONNECT the ISC-BPA power lead.
4. START engine and operate at 1,500 RPM for 20 seconds.
5. Let engine idle and check Base Idle Speed (525±25 RPM).

NOTE: Engine may stall when ISC-BPA is DISCONNECTED. This is acceptable as long as the throttle plate is not stuck in the bore.

6. Adjust as follows:
a. DISCONNECT throttle cable.
b. Adjust engine RPM to within range in Step 5 by TURNING the throttle plate stop screw.
c. RECONNECT throttle cable and REPEAT Step 5.
7. Shut engine OFF and RECONNECT power lead to ISC-BPA.
8. Verify throttle plate is NOT stuck in the bore by exercising throttle plate.

NOTE: If excessive engine idle speeds are experienced when driving the vehicle on the idle system, TURN the ignition switch to OFF position and restart.