MINIMUM IDLE SPEED ADJUSTMENT PROCEDURE IS OUTLINED

MODEL AND YEAR: 1987-88 CAVALIER, CORSICA, BERETTA WITH 2.0L (VIN CODE 1) ENGINE

The 1987 Cavalier and Corsica/Beretta preliminary shop manuals describe a procedure to adjust the minimum idle speed. The procedure involves grounding the diagnostic terminal with the key on (engine not running) to drive the Idle Air Control (IAC) valve fully extended. This procedure should not be followed when setting the minimum idle speed on 1987 2.OL 4 cylinder engines.

NOTE: THIS ADJUSTMENT SHOULD BE PERFORMED ONLY WHEN THE THROTTLE BODY REQUIRES REPLACEMENT. COMPLETE TBI UNITS ARE FACTORY ADJUSTED AND SHOULD NOT BE RESET AT DEALERSHIPS.

The 1987 Cavalier final service manual provides a new procedure involving plugging the IAC valve air passage. In addition, another satisfactory method for checking and/or adjusting the minimum idle speed has been developed. Either method is applicable to the 1987 Cavalier and current 1987-88 Corsica/Beretta with 2.OL engine. Both procedures are listed below.

PROCEDURE A (Shop Manual Revised Manual Method)

1. Remove the T.B.I. bonnet and gasket.

2. Pierce the idle stop screw plug with an awl and apply leverage to remove it.

3. Connect tachometer to engine or use "Scan" tool to check engine RPM.

4. Set parking brake and block drive wheels.

5. Start engine, put transmission in park (neutral on manual transmission) and allow engine RPM to stabilize.

6. Disconnect idle air control connector.

7. Install tool J-36377 - Kent Moore or BT 8528A -Burroughs, or equivalent, in idle air passage of TBI unit. (Verify that no air leaks around the tool).

8. On vehicles with automatic transmissions, place selector lever in D (drive) before making adjustment.

9 Adjust idle stop screw to obtain 650 + 25 RPM.

10. On vehicles with automatic transmission, place selector lever in P (park). Turn ignition "off", remove IAC passage plug tool and reconnect IAC valve electrical connector.

11. Use silicone sealant, or equivalent to cover minimum air adjustment screw.

12. Install TBI bonnet (replace gasket if necessary).

PROCEDURE B (Alternative Method)

1. Remove TBI bonnet and gasket.

2. Pierce the Minimum Air Adjustment Screw plug with an awl and apply leverage to remove it.

3. Connect a "Scan" tool to monitor IAC counts and engine RPM.

4. Set parking brake and block drive wheels.

5. Put transmission in P (park), neutral on manual transmission, start engine and allow engine RPM to stabilize.

6. Create a vacuum leak by removing a vacuum hose to a manifold vacuum source. Allow vacuum leak to remain until "0" IAC counts are shown on "Scan" tool.

7. With IAC counts at 0, disconnect Idle Air Control Valve electrical connector.

8. Reconnect vacuum hose.

9. On vehicles with automatic transmission, place selector lever in D (drive) before making adjustment.

10. Adjust Minimum Air Adjustment Screw to obtain 650 plus or minus 25 RPM.

11. Turn ignition "OFF" and reconnect IAC valve electrical connector.

12. Use silicone sealant, or equivalent, to cover Minimum Air Adjustment Screw.

13. Install TBI bonnet (replace gasket if necessary).

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.