For 1990-2009 cars

# ISC OR ILC ADJUSTMENT REVISED SERVICE PROCEDURE

DEALER SERVICE PERSONNEL ARE REQUESTED TO MAKE THE FOLLOWING CHECK AS AN ADDITION TO THE PROCEDURE LISTED IN SECTION 6C OF THE 1981 SERVICE MANUAL COVERING ADJUSTMENT OF THE IDLE SPEED CONTROL (ISC) OR IDLE LOAD COMPENSATOR (ILC) ON 2 AND 4 BBL. CARBURETOR MODELS USED ON 1981 VEHICLES EQUIPPED WITH 2.5L, 3.8L, 4.3L AND 5.0L ENGINES. IDLE SPEED CONTROL (ISC) 1.PRIOR TO ADJUSTMENT OF THE ISC, CHECK FOR AN IDENTIFICATION LETTER APPEARING ON THE ISC ADJUSTMENT SCREW PLUNGER, FIGURE 1. IF LETTER APPEARS, PROCEED TO STEP 3, BELOW. 2.IF NO LETTER APPEARS, USING TOOL J-29607, REMOVE PLUNGER FROM ISC UNIT. THEN, MEASURE LENGTH OF PLUNGER FROM BACK SIDE OF PLUNGER HEAD TO END OF PLUNGER SCREW, DIMENSION "A", FIGURE 1. RECORD THIS MEASUREMENT FOR USE AT STEP 4, BELOW. REINSTALL PLUNGER SCREW IN ISC UNIT, TURNING PLUNGER IN TO A PRESET POSITION SO THAT THE DISTANCE MEASURED FROM THE BACK SIDE OF THE PLUNGER HEAD TO THE ISC NOSEPIECE IS LESS THAN DIMENSION "B", FIGURE 1. 3.PROCEED WITH ISC ADJUSTMENT AS OUTLINED ON PAGES 6C-66 AND 6C-67 IN THE 1981 FULL SIZE SERVICE MANUAL AND PAGE 6C-9 OF THE 1981 SKYLARK SERVICE MANUAL. 4.AFTER FINAL ADJUSTMENT OF THE ISC PLUNGER, MEASURE DISTANCE FROM BACK SIDE OF PLUNGER HEAD TO ISC NOSEPIECE, DIMENSION "B", FIGURE 1. DIMENSION MUST NOT EXCEED THAT SHOWN BY PLUNGER TYPE AS EITHER IDENTIFIED BY PLUNGER LENGTH OR LETTER IDENTIFICATION. IDLE LOAD COMPENSATOR (ILC) (PAGES 6C-57 & 6C-62 IN THE 1981 BUICK SERVICE MANUAL) AFTER FINAL ADJUSTMENT OF THE ILC PLUNGER, MEASURE DISTANCE FROM JAM NUT TO TIP OF THE PLUNGER, DIMENSION "A", FIGURE 2. DIMENSION MUST NOT EXCEED 25 MM (1").

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.