For 1990-2009 cars

# POWER BRAKE PEDAL EFFORT PROPER ENGINE ADJUSTMENT

IT IS IMPORTANT THAT THERE IS A COMPLETE UNDERSTANDING OF THE NEED FOR PROPERLY SETTING ENGINE ADJUSTMENTS TO PUBLISHED SPECIFICATIONS TO ASSURE GOOD VEHICLE PERFORMANCE. ALL VEHICLE EMISSION LABEL INSTRUCTIONS SHOULD BE CAREFULLY FOLLOWED. SPECIFIC ITEMS FOR ATTENTION ARE: SPARK TIMING - IMPROPERLY SET INITIAL TIMING CAN RESULT IN GENERALLY POOR ENGINE PERFORMANCE, SURGE, SPARK KNOCK, POOR FUEL ECONOMY, ETC. REFER TO THE VEHICLE EMISSION CONTROL LABEL FOR PROPER ADJUSTMENT PROCEDURE AND SPECIFICATIONS. FAST IDLE SPEED - IF FAST IDLE SPEED REQUIRES CORRECTION, IT SHOULD BE PROPERLY SET USING PROCEDURES AND SPECIFICATIONS SHOWN ON THE VEHICLE EMISSION CONTROL LABEL. THE FAST IDLE SPEED CHECK AND ADJUSTMENT IS TO BE PERFORMED WITH WARM ENGINE AND TRANSMISSIONS IN "PARK". SETTING THE SPEED ABOVE THE SPECIFIED RPM OF 1800 SHOULD BE AVOIDED. DO NOT ATTEMPT TO ADJUST CARB IDLE SPEED AS THIS IS CONTROLLED BY THE ECM. NOTICE: AN ACCURATELY CALIBRATED TACHOMETER IS ESSENTIAL WHEN PERFORMING IDLE SPEED ADJUSTMENTS. HIGH FAST IDLE SETTINGS CAN RESULT IN: POOR FUEL ECONOMY. INCREASED BRAKE PEDAL EFFORT DUE TO REDUCED AVAILABLE MANIFOLD VACUUM FOR POWER ASSIST. (DRIVERS WHO BRAKE WITH THEIR LEFT FOOT PRIOR TO COMPLETELY RELEASING ACCELERATOR PEDAL WILL FURTHER REDUCE AVAILABLE VACUUM.) NOTE: ENGINE INITIAL "BREAK-IN" HAS AN EFFECT ON FAST IDLE SPEED. FAST IDLE SPEED IS FACTORY SET BELOW 1800 RPM AND WOULD BE EXPECTED TO INCREASE TO APPROXIMATELY 1800 RPM AFTER INITIAL "BREAK-IN". CONSEQUENTLY, UNLESS NECESSARY TO SATISFY UNUSUAL HIGH IDLE SPEED COMPLAINTS, THE ADJUSTMENTS TO FAST IDLE SPEEDS INDICATED IN THIS BULLETIN SHOULD BE APPLIED ONLY AFTER THE VEHICLE HAS ACCUMULATED APPROXIMATELY 1000 MILES AND SHOULD NEVER BE SET ABOVE LISTED SPECIFICATIONS. SHOULD YOU REQUIRE ADDITIONAL ASSISTANCE IN RESOLVING AN OWNER COMPLAINT, PLEASE CONTACT YOUR DISTRICT SERVICE MANAGER.

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.