ROUGH IDLE AFTER HOT RE-START. Buick Riviera 1995

SUBJECT: ROUGH IDLE AFTER HOT RESTART (REPLACE FUEL PRESSURE REGULATOR AND MEM-CAL)

MODELS: 1995 BUICK RIVIERA WITH 3800 SUPERCHARGED ENGINE (VIN 1 - RPO L67)

CONDITION:

SOME OWNERS MAY COMMENT ABOUT A 20-30 SECOND ROUGH IDLE CONDITION AFTER A HOT RE-START. THIS CONDITION MAY BE MOST NOTICEABLE AFTER THE VEHICLE HAS BEEN DRIVEN UNTIL FULLY WARMED UP, PARKED FOR ABOUT 1/2 HOUR, AND THEN RESTARTED.

CAUSE:

THE COMBINATION OF A HIGH RVP (REID VAPOR PRESSURE) FUEL BLEND ALONG WITH HIGH FUEL RAIL TEMPERATURES AND LOW FUEL RAIL PRESSURE CREATES A CONDITION WHERE THE FUEL IN THE RAIL AND/OR INJECTORS BEGINS TO VAPORIZE. THE VAPORIZATION CAUSES BUBBLES TO FORM AND CREATES A ROUGH IDLE CONDITION UNTIL THE AIR IS PURGED FROM THE FUEL SYSTEM (USUALLY 20 - 30 SECONDS). IMPORTANT: HIGH ALTITUDE ALSO MAKES THE CONDITION WORSE.

CORRECTION:

1. CHECK FOR AND REPAIR ANY DIAGNOSTIC TROUBLE CODES THAT MAY BE PRESENT.

2. INSTALL A 1996 DESIGN FUEL PRESSURE REGULATOR WHICH WILL INCREASE THE FUEL SYSTEM PRESSURE FROM 39 PSI TO 52 PSI (MEASURED WITH VACUUM HOSE DISCONNECTED).

3. INSTALL THE REVISED MEM-CAL.

IMPORTANT: BOTH THE FUEL PRESSURE REGULATOR AND THE REVISED MEM-CAL MUST BE INSTALLED DURING THE SAME REPAIR VISIT.

PARTS INFORMATION FUEL PRESSURE REGULATOR 24503229 SERVICE MEM-CAL 16244168

PARTS ARE EXPECTED TO BE AVAILABLE MAY 6, 1996 FROM GMSPO.

WARRANTY INFORMATION

LABOR OPERATION DESCRIPTION LABOR TIME J6364 MEM-CAL - REPLACE USE PUBLISHED LABOR OPERATION TIME. J5560 REGULATOR, FUEL PRESSURE - REPLACE USE PUBLISHED LABOR OPERATION TIME.

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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.