EXCESSIVE OIL CONSUMPTION, MISS, ROUGH IDLE OR SPARK PLUG. GMC Truck GMC K Pickup

REVISION: 11/14/96

THIS BULLETIN IS BEING REVISED TO ADD A NOTE AND PROVIDE NEW INFORMATION IN THE CORRECTION SECTION OF THIS BULLETIN. PLEASE DISCARD CORPORATE BULLETIN NUMBER 57-61-15. ----------------------------------------------------------------------

SUBJECT: EXCESSIVE OIL CONSUMPTION, MISS, ROUGH IDLE OR SPARK PLUG FOULING (CYLINDER HEAD ASSEMBLY EXCHANGE PROGRAM)

MODELS: 1995 CHEVROLET AND GMC TRUCK C/K, G, AND P MODELS WITH 7.4L ENGINE (VIN N - RPO L19)

THE FOLLOWING VIN RANGES ARE KNOWN TO BE POSSIBLE FOR OIL CONSUMPTION, HOWEVER, A FEW VEHICLES WITH VINS OUTSIDE THE GIVEN RANGES MAY BE AFFECTED.

ASSEMBLY BEGINNING DIVISION MODEL PLANT VIN ENDING VIN --------------------------------------------------------- CHEVROLET C/K PONTIAC EAST SE134818 SE187614 --------------------------------------------- JANESVILLE SJ106360 SJ107539 --------------------------------------------- SJ312068 SJ357352 --------------------------------------------- G FLINT SF140448 SF174637 --------------------------------------------- P DETROIT S3304849 S3313508 --------------------------------------------------------- GMC C/K PONTIAC EAST SE509301 SE520710 --------------------------------------------- JANESVILLE SJ510634 SJ512083 --------------------------------------------- SJ712196 SJ722924 --------------------------------------------- G FLINT SF518190 SF522281 --------------------------------------------- P DETROIT S3501165 S3501873 ---------------------------------------------------------

IMPORTANT: THE EXCHANGE PROCEDURE DESCRIBED IN CORPORATE BULLETIN 57-61-15 IS NO LONGER IN EFFECT. IF A REPLACEMENT CYLINDER HEAD IS NECESSARY, REFER TO THE CORRECTION STATEMENT IN THIS BULLETIN.

CONDITION:

SOME OWNERS MAY COMMENT ON EXCESSIVE OIL CONSUMPTION, ENGINE MISS OR ROUGH IDLE. VEHICLES AFFECTED MAY EXHIBIT SPARK PLUG FOULING ON ONLY ONE BANK OF CYLINDERS OR ONLY ONE OR TWO INDIVIDUAL SPARK PLUGS.

CAUSE:

THE AFFECTED CYLINDER HEAD MAY HAVE BEEN MIS-MACHINED WHICH ALLOWS OIL TO BE DRAWN INTO THE ENGINE BY INTAKE MANIFOLD VACUUM WHERE THE INTAKE VALVE GUIDE IS PRESSED INTO THE CYLINDER HEAD.

CORRECTION:

REPLACE THE EXISTING CYLINDER HEAD ASSEMBLY WITH A NEW CYLINDER HEAD. THE CYLINDER HEAD ASSEMBLY IS AVAILABLE THROUGH GMSPO. WHENEVER A NEW CYLINDER HEAD ASSEMBLY IS ORDERED, THE VALVES, SPRINGS, CAPS AND KEEPERS MUST BE INSTALLED INTO THE NEW CYLINDER HEAD CASTING. A NEW CYLINDER HEAD GASKET AND INTAKE GASKET SHOULD BE INSTALLED.

WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR DESCRIPTION OPERATION LABOR TIME

RIGHT BANK J0510 USE PUBLISHED LABOR OPERATION TIME. LEFT BANK J0511 USE PUBLISHED LABOR OPERATION TIME. BOTH BANKS J0517 USE PUBLISHED LABOR OPERATION TIME.

FIGURES: 0 ATTACHMENTS: 0

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.