Engine - Backfire Upon Acceleration

File in Section: 6E - Engine Fuel & Emission

Bulletin No.: 47-65-22

Date: January, 1995

Subject:
Backfire on Acceleration (Correct Calibration)

Models:
1994 Chevrolet and GMC Truck S/T Models with 4.3L Engine (VIN Z - RPO LB4) and Manual Transmission (RPO MY2)

Condition

Some owners may experience a backfire condition upon acceleration.

Cause

Insufficient ignition timing advance in the spark calibration under some driving conditions.

Correction

More robust calibrations have been released to address this concern. THIS CALIBRATION WILL NOT CORRECT ANY OTHER DRIVEABILITY CONCERN.

Important:
These service calibrations should ONLY be used if a backfire concern still exists in a vehicle WHICH HAS HAD THE BASE TIMING CHECKED AND SET TO SPECIFICATION.

LAUNCH DETONATION MAY OCCUR IN VEHICLES SERVICED WITH THESE CALIBRATIONS;
particularly in vehicles which are heavily loaded or towing trailers.





Parts Information

Service "FLASH" calibrations are available starting with the December, 1994 CD ROM.





Warranty Information