Service Procedures: Overview

1. Perform normal diagnosis to be sure that no hard fault is present. Refer to the 1993 Powertrain Control/Emissions Diagnosis (PC/ED) Service Manual for MIL lamp concerns. Normal diagnosis should also include checking the following:

^ Exhaust Gas Recirculation (EGR) valve and passages to be sure they are not plugged with deposits

^ EGR valve to be sure it opens when vacuum is applied to the valve (engine will stall if idling)

^ EGR valve to be sure it is fully closed when vacuum is released

^ Follow vacuum lines and connections for any possible leaks or obstructions, to include:

^ Vacuum line between the intake manifold and the Electronic Vacuum Regulator (EVR) solenoid

^ Vacuum line between the EVR solenoid and the EGR valve

^ Vacuum boots on all connections EVR solenoid for proper function

2. If either a hard fault is present or DTCs 327 or 332 (31 and 32 for 1988-91 models) are indicated in "Key On Engine Off' (KOEO) and "Key On Engine Running" (KOER) Self Test modes, or continuous memory mode, then service with a large port PFE sensor, if indicated.

NOTE:
IF THIS KIT HAS ALREADY BEEN PREVIOUSLY INSTALLED, SERVICE WITH THE APPROPRIATE INDIVIDUAL LARGE PORT COMPONENT. ONLY LARGE PORT COMPONENTS SHOULD BE USED FOR SERVICE FOR THIS VEHICLE.

NOTE:
DO NOT REPLACE THE SENSOR IF WATER IS FOUND IN THE SYSTEM, BUT NO CODES ARE SET. WATER IS A NATURAL BY-PRODUCT OF COMBUSTION AND HAS NO ADVERSE AFFECT ON THE PERFORMANCE OF THE PFE SENSOR.

NOTE:
DO NOT REPLACE THE PFE SENSOR IF DRIVEABILITY CONCERNS SUCH AS ROLLING/ROUGH IDLE, STUMBLE OR SURGE ARE PRESENT BECAUSE THE EGR IS NORMALLY TURNED OFF BY THE ELECTRONIC ENGINE CONTROL (EEC) STRATEGY IN THE EVENT OF THE PFE SENSOR MALFUNCTION, AND THESE SYMPTOMS WILL NOT OCCUR WITH A FAILED PFE SENSOR.

NOTE:
REPLACE THE PFE SENSOR IF:

^ A CONTINUOUS MEMORY CODE HAS BEEN SET
^ A HARD FAILURE OF THE SENSOR HAS BEEN DOCUMENTED
^ EITHER OF THE DTCs APPEAR (ONLY) OR A PFE SENSOR "HARD FAILURE" IS INDICATED