MINIMUM IDLE SPEED ADJUSTMENT PROCEDURE IS OUTLINED

MODELS AFFECTED: 1987 SKYHAWK WITH LL8 2.0L L-4 ENGINE (VIN CODE 1)

Use one of the following procedures:

Chassis Service Manual Procedure:

Update:

For the "idle air passage plugging tool" procedure, as defined in the 1987 Buick Chassis Service Manual, Section 6E2-C2, two service tools (or their equivalent) can be used. They are J-36377 (new - available May, 1987), and BT 8528A (new).

Optional Procedure:

An optional procedure for setting minimum idle speed when replacing a lower TBI assembly is defined as follows: (This "optional procedure" can be used when the idle air passage plugging tool is not available.)

REVISED MINIMUM IDLE SPEED ADJUSTMENT PROCEDURE FOR 2.0L (VIN 1) ENGINE:

This adjustment should be performed onlv when the lower throttle body assembly has been replaced. ComDlete TBI units are factory adjusted and should not be reset in the field. Engine should be at normal operating temperature before makinq adjustment.

IMPORTANT: The throttle stop screw, used for regulating minimum idle speed, is adjusted at the factory. The screw is covered with a plug to discourage unauthorized adjustments. However, if it is necessary to gain access to the Minimum Air Adjustment Screw, the following procedure eliminates removal of the TBI unit froin the manifold.

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 park (Neutral on manual transmission), start engine and allow engine RPM to stabilize.

6. Create a vacuum leak by removing a vacuum hose from 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 the IAC valve electrical connector.

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

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

This service bulletin is for information only.

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.