INTERMITTENT FAST/ROUGH IDLE A/C COMPRESSOR ENGAGED. Cadillac Cimarron 1982

For 1990-2009 cars

# INTERMITTENT FAST/ROUGH IDLE A/C COMPRESSOR ENGAGED

#### MODELS AFFECTED: 1982 CIMARRONS

Some 1982 Cimarrons may experience a rough, unstable or intermittent fast idle when the A/C compressor is engaged as a result of an incorrectly adjusted ISC. The following is a revised procedure that should be used when setting the ISC minimum and maximum authority.

This revised procedure makes it easier to jumper the ISC motor circuitry required to extend and retract the plunger. This procedure should be used in place of the procedure listed on pages 6C1-11 and 12 of the 1982 Cimarron Service Information Manual.

When servicing an idle speed control (ISC) assembly, a base (minimum authority) and high (maximum authority) RPM speed check must be performed and adjustments made as required. These adjustments limit the low and high RPM speeds to the ECM. When making a low and high speed adjustment, 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. The ISC minimum should be set to 700 RPM and the ISC maximum should be set to 1500 RPM.

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

1. Connect tachometer (distributor side of tach filter, if used).

2. Connect dwell meter to mixture control (M/C) solenoid dwell lead. Remember to set dwell meter on the six cylinder scale, regardless of the engine being tested.

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. Remove two fasteners which secure the bracket for the idle speed control relay, vacuum sensor and canister purge solenoid valve mounted on RH strut tower and unplug idle speed control relay electrical connector.

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

7. Fully retract ISC plunger by applying 12 volts to circuit #926 (dark green wire) and ground circuit #925 (light green wire) at the ISC relay connector.

#### NOTICE: Leave connector disconnected. Do not leave battery voltage applied to motor longer than recessary to retract ISC plunger. Prolonged contact may damage motor.

8. Start engine and wait untit dwell meter needle starts to vary, indicating "closed loop" operation.

9. With parking brake applied and drive wheels blocked, place transmission in drive (neutral - manual transmission models).

10. With ISC plunger fully retracted, adjust carburetor base (slow) idle stop screw to 700 RPM.

11. Place transmission in "park" or neutral and fully extend ISC plunger by applying 12 volts to circuit #925 (light green wire) and ground circuit #926 (dark green wire) at the ISC relay connector until the plunger fully extends.

#### NOTICE: Leave connector disconnected.

12. With ISC plunger fully extended, using tool J-29831 or equivalent, turn ISC plunger to obtain 1500 RPM maximum authority. Verify ISC adjustment with voltage applied to motor; motor will ratchet in and out.

Retract ISC plunger as outtined in Step #7 to avoid engine dieseling.

13. Place transmission in park or neutral and turn ignition "OFF." Disconnect 12-volt DC power source, jumper leads, ground lead, tachometer, and dwell meter.

14. With ignition "OFF" reconnect the ISC relay and install bracket assembly removed in Step #6.

15. "Tricking"the ISC motor as described in this procedure will cause the "check engine" light to come on and an ISC motor trouble code to be set. By restoring the system to normal operation, the light will go out, but the trouble code will continue to be stored as an "intermittent" problem. It will be necessary to clear the diagnostic trouble code as outlined in Section 6E of the 1982 Cimarron Service Information Manual.

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.