INTERMIT. ENG. MISS ON START UP. Chevrolet Monte Carlo 1998

SUBJECT: INTERMITTENT ENGINE MISS ON START UP (REPROGRAM PCM)

MODELS: 1998 CHEVROLET LUMINA, MONTE CARLO WITH 3100 V6 ENGINE (VIN M--RPO L82)

CONDITION:

SOME OWNERS MAY EXPERIENCE AN INTERMITTENT ROUGH IDLE OR MISFIRE AT IDLE AFTER THE ENGINE IS STARTED. IF THE ENGINE IS TURNED OFF AND THEN RESTARTED, THE CONDITION MAY NOT REAPPEAR. ADDITIONALLY, SOME OWNERS MAY ALSO EXPERIENCE LACK OF POWER ON A PARTIAL THROTTLE ACCELERATION IN THE 1600-2000 ERPM (ENGINE REVOLUTIONS PER MINUTE) RANGE.

CAUSE:

FOR VEHICLES THAT EXPERIENCE A ROUGH IDLE OR MISFIRE, THE CAUSE IS THE IGNITION SYSTEM'S UNFILTERED SIGNAL INPUT TO THE POWERTRAIN CONTROL MODULE (PCM) FROM THE 7X CRANK SENSOR. DUE TO THE LOCATION OF THE PCM THE SIGNAL IS SUSCEPTIBLE TO ELECTROMAGNETIC INTERFERENCE (EMI). FOR VEHICLES THAT EXPERIENCE A LACK OF POWER ON AN ACCELERATION EVENT, THE CAUSE IS THE KNOCK SENSOR SYSTEMS SENSITIVITY TO CERTAIN NATURAL ENGINE OPERATING FREQUENCIES. A SERVICE TECHNICIAN WOULD SEE THIS ON A SCAN TOOL AS THE KNOCK SENSOR RETARDING THE IGNITION SYSTEMS TIMING ADVANCE TYPICALLY IN THE 15 DEGREES OF RETARD RANGE WHILE OPERATING BETWEEN 1600-2000 ERPM.

CORRECTION:

A NEW FLASH PROM CALIBRATION HAS BEEN RELEASED FOR THESE CONDITIONS.

PARTS INFORMATION THE NEW FLASH PROM CALIBRATIONS WILL BE AVAILABLE FROM THE SERVICE TECHNOLOGY GROUP ON CD 17 FOR 1997.

FLASH CALIBRATION EMISSIONS

9352714 USA FEDERAL INCLUDING CANADA

9352634 USA CALIFORNIA

9352724 UNLEADED FUEL EXPORT

9352734 LEADED FUEL EXPORT

IMPORTANT: THERE ARE THREE METHODS FOR PROGRAMMING A PCM:

1. DIRECT PROGRAMMING. THE VEHICLE IS DIRECTLY CONNECTED VIA THE DATA LINK CONNECTOR (DLC) ON THE DEALERS/RETAILERS TECHLINE EQUIPMENT. (T-20 PLUS, T-50 AND T-60 ONLY) VEHICLE MUST BE PRESENT.

2. REMOTE PROGRAMMING. THE NEW PROGRAM IS DOWNLOADED INTO THE DEALERS/RETAILERS SCAN TOOL AND THEN DOWNLOADED INTO THE VEHICLE FROM THE SCAN TOOL VIA THE DLC. TECH 2 REQUIRED. VEHICLE MUST BE PRESENT.

3. OFF-CAR PROGRAMMING. A PCM MAY BE PROGRAMMED WHILE REMOVED FROM THE VEHICLE BY USING THE OFF-BOARD PROGRAMMING ADAPTER (OBPA), P/N 41207- B. THIS ADAPTER CAN BE CONNECTED TO EITHER THE TECHLINE TERMINAL FOR DIRECT PROGRAMMING OR THE SCAN TOOL FOR REMOTE PROGRAMMING. NOT NECESSARY FOR THE VEHICLE TO BE PRESENT.

REFER TO THE APPROPRIATE SERVICE MANUAL OR TECHLINE INFORMATION FOR MORE DETAILED INSTRUCTIONS.

IMPORTANT: DO NOT ATTEMPT TO ORDER THE CALIBRATIONS FROM GMSPO. THE CALIBRATIONS ARE PROGRAMMED INTO THE VEHICLE'S PCM VIA A TECHLINE TOOL DEVICE.

WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR CODE: J6352 REPROGRAMMING, PROM ON CAR LABOR TIME: USE PUBLISHED LABOR OPERATION TIME.

LABOR CODE: J6355 REPROGRAMMING, PROM OFF CAR LABOR TIME: USE PUBLISHED LABOR 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.