NO START/HIGH IDLE AT START CHANGE PCV SYSTEM

SOME VEHICLES MAY EXPERIENCE ICE FORMATION ON THE THROTTLE SHAFT OF THE CARBURETOR AFTER AN EXTENDED PARK PERIOD IN FREEZING CONDITIONS. THE FORMATION OF ICE MAY CAUSE A NO START OR HIGH IDLE SPEED SYMPTOM WHEN THE ENGINE IS RESTARTED. THE FORMATION OF ICE AT THE THROTTLE SHAFT IS CAUSED BY MOISTURE BEING CARRIED FROM THE AREA UNDER THE CYLINDER HEAD COVER, THROUGH THE AIR CLEANER, INTO THE CARBURETOR INSTEAD OF TO THE INLET MANIFOLD DIRECTLY BELOW THE CARBURETOR - AS SHOWN IN FIGURE 1. THIS IMPROPER ROUTING OF MOISTURE THROUGH THE CARBURETOR CAN OCCUR WHEN THE PCV SYSTEM REGULAT- ING ORIFICE LOCATED IN THE INTAKE MANIFOLD BECOMES RESTRICTED BY ICE. THE MOISTURE PASSING THROUGH THE CARBURETOR SETTLES ON THE THROTTLE SHAFT WHEN THE ENGINE IS SWITCHED OFF AT THE TIME THE CAR IS PARKED. THIS MOISTURE SUBSEQUENTLY FREEZES FORMING ICE IN THE THROTTLE SHAFT BEARING SURFACE AREA. UPON SETTING THE CHOKE TO RESTART THE ENGINE, THIS ICE BUILD UP MAY CAUSE THE THROTTLE POSITION TO BE SET AT A MORE OPEN POSITION THAN REQUIRED FOR ENGINE STARTING. TO PREVENT FUTURE OCCURRANCE OF THIS CONDITION, THE 1987 MODEL VEHICLE INCORPORATES A REVISED PCV SYSTEM UTILIZING A PCV VALVE LOCATED IN THE CYLINDER HEAD COVER (AT 'A' IN FIGURE 1) AND ELIMINATES THE REGULATING ORIFICE IN THE INTAKE MANIFOLD. CORRECTIVE ACTION FOR VEHICLES EXHIBITING THE DESCRIBED SYMPTOMS IS AS FOLLOWS: 1. REMOVE CYLINDER HEAD COVER AND GASKET 2. REMOVE CARBURETOR AND EFE HEATER. 3. COVER OPEN INTAKE HOLES IN MANIFOLD TO PREVENT ENTRY OF FOREIGN MATERIAL. 4. DISCONNECT THE PCV HOSE FROM THE REGULATING ORIFICE AT THE INTAKE MANIFOLD. 5. USING A 2.5MM DIAMETER (.098 IN.) DRILL, DRILL OUT THE REGULATING ORIFICE. 6. REMOVE ALL METAL RESIDUE REMAINING AFTER THE DRILLING OPERATION FROM THE INSIDE OF THE INTAKE MANIFOLD. 7. RECONNECT PCV HOSE, REINSTALL THE HEATER, CARBURETOR AND AIR CLEANER. 8. INSTALL NEW CYLINDER HEAD COVER (1987 PART) AND GASKET, HEAD COVER BOLT GASKET, CAP-OIL FILL (1985 ONLY) AND GASKET-OIL FILL. (FOR 1986 MODEL, EXISTING OIL FILL CAP CAN BE REUSED), PCV VALVE AND RECONNECT HOSES. PART NUMBERS OF THE REQUIRED PARTS AND THEIR APPLICATION ARE LISTED BELOW: QTY. PART NAME PART NUMBER MODEL YEAR _____ ___________ __________ __________ 1 COVER-CYLINDER HEAD 94421664 85-86 1 GASKET-CYLINDER HD. COVER 94250970 85-86 1 CAP-OIL FILL HEAD COVER 94408585 1985 ONLY 1 GASKET-OIL FILL CAP 94123623 85-86 1 GASKET-HEAD COVER BOLT 94251069 85-86 1 VALVE - CRANKCASE VENT 94419564 85-86 LABOR OPERATION NUMBER: T1191 LABOR TIME : 1.8 HOURS

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.