Idle/Throttle Speed Control Unit: Adjustments

PROCEDURE
When a new Idle Speed Control (ISC) assembly is installed, a base (minimum) and extended (maximum) RPM speed check must be performed and adjustments made as required. When making low and high speed adjustments, the low speed adjustment is always made first. DO NOT use the ISC plunger to adjust curb idle speed as the idle speed is controlled by the ECM.

Before starting engine place transmission selector lever in Park or Neutral, set parking brake and block drive wheels.

Prior to adjustment, check for identification letter on the ISC adjustment plunger. Adjust plunger, if required, to Dimension "B".

CAUTION: Do not disconnect or connect ISC connector with ignition "ON", as damage to the ECM may occur.

1. Connect tachometer.
2. Connect a dwell meter to mixture control (M/C) solenoid dwell (green) lead. Set dwell meter on the six cylinder scale.
3. Turn A/C "OFF".
4. Start engine and run until stabilized by entering "Closed Loop" (dwell meter needle starts to vary).
5. Turn ignition "OFF".
6. Unplug connector from ISC motor.
7. Fully retract ISC plunger by applying 12 volts to terminal "C" of the ISC motor connection and ground lead to terminal "D" of the ISC motor connection. It may be necessary to install jumper leads from the ISC motor in order to make proper connections.

CAUTION: DO NOT leave battery voltage applied to motor longer than necessary to retract ISC plunger. Prolonged contact will damage motor. Also, NEVER connect voltage source across terminals "A" and "B" as damage to the internal throttle contact switch will result.

8. Start engine and wait until dwell meter needle starts to vary, indicating "Closed Loop" operation.
9. With parking brake applied and drive wheels blocked, place transmission in "Drive".
10. With ISC plunger fully retracted, adjust carburetor base (slow) idle stop screw if required to obtain minimum rpm idle speed.
11. Place transmission in "Drive" and fully extend ISC plunger by applying 12 volts to terminal "D" of the ISC motor connection and ground lead to terminal "C" is the ISC motor connection. Apply voltage only long enough to extend plunger.

CAUTION: When the plunger is in the fully extended position, the plunger must be in the contact with the throttle lever to prevent possible internal damage to unit.

12. Place transmission in "DRIVE".
13. With ISC plunger fully extended, check maximum rpm. Adjust ISC plunger if required using tool J29607, BT-8022 or equivalent to obtain maximum rpm speed.
14. Recheck Maximum rpm adjustment with voltage applied to ISC motor. Motor will ratchet at full extension with power applied. Re-adjust if necessary.
15. Place transmission in Park or Neutral and turn ignition "OFF". Disconnect 12 volt DC power source,jumper leads, ground lead and tachometer.
16. Reconnect 4 terminal harness connector to ISC motor.
17. Remove blocks from drive wheels.