Introduction

General Motors has released many service bulletins and calibration MEM-CALS to correct driveability concerns during the 1987 through 1990 model years for the 2-8/3.1 liter applications. This handy pocket guide will allow the technician to easily select the proper bulletin and MEM-CAL using the customer complaint as the reference for determining the correct diagnostic procedure. This guide contains our latest driveability MEM-CALS and bulletin updates. All previous 2.8/3.1 liter driveability complaint bulletins should not be used. It is important to remember that the 2.8/3.1 liter engine uses "Closed Loop" fuel and spark control technology. For this reason, it is very important that all of the engine components and the base engine assembly are in proper working order. The Electronic Control Module (ECM) uses the inputs from its sensors as the basis for calculating fuel and spark. A component that is not functioning properly will cause false values to be used in the closed loop fuel and spark calculations resulting in a possible driveability complaint by the customer. This guide is not intended to take the place of the Service Manual for diagnosis, but to assist the technician as a quick reference to bulletins, MEM-CALS and correct engine parameters when using a TECH 1 scan tool.