PRIMARY VACUUM BREAK SETTINGS NON CLOSED LOOP EMISSIONS

TO ASSIST IN PROVIDING BETTER ENGINE CHOKE UNLOADING AND MINIMIZE SPARK PLUG FOULING, PRIMARY VACUUM BREAK SETTINGS HAVE BEEN REVISED FROM 18F TO 22F. THIS REVISED SETTING MAY HAVE A TENDENCY TO INCREASE THE PROBABILITY OF A "STALL AFTER START". USE THE FOLLOWING CHART AS AN AID IN DETERMINING THE APPROPRIATE SERVICE ACTION. ORIGINAL V.B. SETTING 18F COMMENT SPARK PLUG "FOULING" LOADING ETC. REVISED V.B. SETTING 22F EXPECTED RESULT IMPROVED LOADING OCCASIONAL "STALL-AFTER-START" ORIGINAL V.B. SETTING 22F COMMENT STALL-AFTER-START REVISED V.B.SETTING 18F EXPECTED RESULT NO STALLS. SOME LOADING DEPENDING ON DRIVING SCHEDULE IN NO CASE SHOULD THE SECONDARY VACUUM BREAK SETTING BE REVISED.

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.