1988 PONTIAC FIERO Service Repair Manual

6E3-C1-10 2.8L (VIN 5) DRIVEABILITY AND EMISSIONS
- 959 DK GRN
BRAKE SWITCH
MANUALTRANS
TO FAN
CONTROL +-- DK GRNMIHT335 - COOLING FAN
RELAY
CHART C-I
ECM QDR CHECK
2.8% (VIN S) 'TI' SERIES (PORT)
ECM Quad Driwer (QDR) Check
The ECM uses an integrated circuit (IC) called a
quad driver
(QDR) in place of separate transistors to
turn "ON" or "OFF" different circuits controlled by
the ECM. Each
QDR has four separate outputs that
can independently turn "ON" or "OFF" four different
circuits.
ECM service part number 1227302, used with this
engine, does not have fault protection, therefor,
a
single faulty circuit many time causes all four QDR
outputs to be inoperative or "OX" all the time.
A
failed QDR usually results in either a shorted or open
ECM output. Because of the increased current
flow,
two QDR outputs are used to drive the TCC solenoid. Refer
to the ECM QDR check procedure on the
facing page. This
check will not test all ECM
functions, but it will determine if a specific circuit has
caused a specific
QDR to fail in the ECM.
A faulty circuit is the largest cause of a failed
QDR, therefore, the check procedure should be used
whenever ECM replacement is indicated, especially if
the removed ECM exhibits characteristics of a
damaged QDR such as:
@ SES light with no code stored.
@ Engine will not start and/or ECM will not
flash Code 12.
@ Flickering, intermittent, or dim SES light.
@ Output, such as TCC circuit, is inoperative or
"ON" at all times.
@ ISngine misfires, surges or stalls.
@ "Scan" tool is erratic or inoperative.

DRlVEABlLlPY AND EMISSIONS 2.8L (VIN S) 6E3-C1-11
USE THIS CHECK PROCEDURE ONLY AFTER OTHER
DIAGNOSTIC CHARTS, IN THIS SERVICE MANUAL HAVE
DETERMINED THAT THERE WAS AN ECM FAILURE.
TERMINAL LISTED, BLACK (NEG.) LEAD TO
RED
(POS.) LEAD TO ECM TERMINAL.
NALS LISTED SHOULD HAVE RESISTANCE OF
EACH VEHICLE
ECM# 1227302
VOLTAGE IN EXCESSIVE
CURRENT DRAW CIRCUIT.
* USE DVM J-34029-A OR EQUIVALENT

6E3-C1-12 2.8L (VIN 5) DRIVEABILITY AND EMISSIONS
15 WAY. (FRONT VIEW)
434 ORNIBLK
450 BLWHT
ENGINE GROUND
CHART C-IA
PARWNEUTRAL SWITCH
2.8L (VIN S) "F" SERIES (PORT)
Circuit Description:
The ParWNeutral Switch contacts are a part of the Neutral Start switch, and are closed to ground in park or
neutral and open in drive ranges.
The ECM supplies ignition voltage, through a current limiting resistor, to CKT
434 and senses a closed
switch, when the voltage on CKT
434 drops to less than one volt.
The
ECM uses the PIN signal as one of the inputs to control:
Idle Air Control
VSS Diagnostics
EGR
If CKT 434 indicates PIN (grounded), while in drive range, the EGR would be inoperative, resulting in
possible detonation.
If CKT 434 always indicates drive (open), a drop in the idle may exist when the gear selector is moved into
drive range.
Test Description: Numbers below refer to circled 2. Checks for an open switch in drive range.
numbers on the diagnostic chart.
3. Be sure "Scan" indicates drive, even while
1. Checks for a closed switch to ground in park wiggling shifter to test for an intermittent or
position. Different makes of "Scan" tools will read misadjusted switch in drive range.
PIN differently. Refer to operator's manual for
type of display used for a specific tool.

DRIVEABILITY AND EMISSIONS 2.8L (WIN S) 6E3-C1-13
T PIN SWITCH. D CAUSE "SCAN" DRIVE RANGE.

6E3-C4-14 2.8L (VIN S) BWiVEABlLlPV AND EMISSIONS
POWER STEERING
PRESSURE SWITCH
PIS PRESSURE
CLOSES
WITH HIGH BLWHT
PRESSURE
-
CHART C-1 E
POWER STEERING PRESSURE SWITCH
2.8L (VIN S) "F"" SERIES (PORT)
Circuit Description:
The power steering pressure switch is normally open to ground, and CKT 901 will be near the battery
voltage. Turning the steering wheel increases power steering oil pressure and its load on an idling engine. The
pressure switch will close before the load can cause an idle problem.
Closing the switch causes CKT 901 to read less than
1 volt. The ECM will increase the idle air rate and
disengage the
A/C relay.
e A pressure switch that will not close, or an open CKT 901 or 450, may cause the engine to stop when
power steering loads are high.
@ A switch that will not open, or a CKT 901 shorted to ground, may affect idle quality and will cause the
NC relay to be de-energized.
Bescription: Numbers below refer to circled 2. Checks to determine if CKT 901 is shorted to
numbers on the diagnostic chart. ground.
1. Different makes of "Scan" tools may display the 3. This should simulate
a closed switch.
state of this switch in different ways. Refer
to
"Scan" tool operator's manual to determine how
this input is indicated.

DRIVEABILITY AND EMISSIONS 2.8L (VIN S) 6E3-C"s-15
@ "SCAN" SHOULD INDICATE "OFF".
JUMPER HARNESS
TERMINALS TOGETHER.
r "SCAN" SHOULD
DISPLAY "ON".
CHASSIS GROUND.

6E3-C1-16 2.8L (VIN S) DRlVEABlLlTV AND EMISSIONS
BLANK

DRIVEABILITY AND EMISSIONS 2.8b (VIN 5) 6E3-C2-1
SECTION C2
FUEL CONTROL SYSEEIVI
CONTENTS
GENERAL DESCRIPTION . . . . . . . . . . . . . . . . C2-1 FUEL RAIL SERVICE . . . . . . . . . . . . . , . . . C2-6
PURPOSE ......................... C2-1 UNIT SERVICE PROCEDURES . . . . . . . . . . . C2-6
MODES OF OPERATION . . . . . . . . . . . . . . C2-1 COLD START TUBE & VALVE ASSEMBLY.. . C2-7
Starting Mode . . . . . . . . . . . . . . . . . . . C2-2 FUEL PRESSURE CONNECTION ASSEMBLY . C2-7
Clear Flood Mode . . . . . . . . . . . . . . . . . C2-2 FUEL BLOCK AND SEAL.. . . . . . . . . . . . . . C2-9
Run Mode .. .. . . . . . . . . . . . . . . . . . . C2-2 FUELINJECTORS .. . . . .. ... .... . . . ... C2-9
Acceleration Mode. . . . . . . . . . . . . . . . C2-2 Port Injectors wl Injector Retaining Clips C2-9
Deceleration Mode . . . . . . . . . . . . . . . C2-2 Fuel Pressure Regulator . . . . . . . . . . . . C2-10
Battery Voltage Correction Mode . . . . . C2-2 PORT INJECTORS . . . . . . . . . . . . . . . . . . . C2-10
Fuel Cutoff Mode . . . . . . . . . . . . . . . . . C2-3 PRESSURE REGULATOR.. . . . . . . . . . . . . . C2-10
Fuel Control System Components . . . . . C2-3 COLD START FUEL INJECTION SWITCH . . . C2-1 I
Basic System Operation. . . . . . . . . . . . . C2-3 THROTTLE BODY . . . . . . . . . . . . . . . . . . . C2-11
THROTTLE BODY UNIT . . . . . . . . . . . . . . . C2-3 THROTTLE BODY SERVICE IDENTIFICATION C2-11
FUEL RAIL.. . . . . . . . . . . . . . . . . . . . . . . . C2-3 MINIMUM IDLE SPEED ADJUSTMENT . . . . C2-14
FUEL INJECTOR.. . . . . . . . . . . . . . . . . . . . C2-3 UNIT REPAIR PROCEDURES . . . . . . . . . . . . C2-14
PRESSURE REGULATOR.. . . . . . . . . . . . . . C2-3 IDLE AIR CONTROL VALVE
IDLE AIR CONTROL (IAC) VALVE
. . . . . . . . C2-4 ASSEMBLY &GASKET.. . . . . . . . . . . . . . . C2-14
FUEL PUMP ELECTRICAL CIRCUIT . . . . . . . C2-4 IDLE AIRIVACUUM SIGNAL
DIAGNOSIS . . . . . . . . . . . . . . . . . . . . . . . . . C2-5 HOUSING ASSEMBLY . . . . . . . . . . . . . . . . C2-15
FUEL CONTROL SYSTEM . . . . . . . . . . . . . . C2-5 COOLANT CAVITY COVER & O-RING . . . . * C2-15
IDLE AIR CONTROL VALVE . . . . . . . . . . . . C2-5 IDLE AIR CONTROL / COOLANT
ON-CAR SERVICE . . . . . . . . . . . . . . . . . . . . . C2-5 COVERASSEMBLY .............,.... C2-16
PORT FUEL INJECTION COMPONENTS . . . . C2-5 FUEL PUMP RELAY . . . . . . . . . . . . . . . . . . C2-17
FUEL PRESSURE RELIEF PROCEDURE . . . . . C2-5 OIL PRESSURE SWITCH . . . . . . . . . . . . . . . C2-17
Plenum ........................ C2-5 PARTS INFORMATION . . . . . . . . . . . . . . . . . C2-17
Fuel Rail & Pressure Regulator Assembly . C2-5
GENERAL DESCRIPTION
PURPOSE
The basic function of the fuel control system is to
control fuel delivery to the engine.
Fuel is delivered to the engine by individual fuel
injectors mounted in the intake manifold near each
cylinder. The main control sensor is the oxygen
(02) sensor,
which is located in the exhaust manifold. The
O2
sensor tells the ECM how much oxygen is in the
exhaust gas, and the ECM changes the airlfuel ratio to
the engine by controlling the fuel injectors. The best
mixture to minimize exhaust emissions is
14.7 to 1,
which allows the catalytic converter to operate the
most efficiently. Because of the constant measuring
and adjusting of the airlfuel ratio, the fuel injection
system is called
a "Closed LoopJ' system (shown in
Figure C2-1).
ELECTRONIC CONTROL MODULE (ECM)
FUEL INJECTORS
EXHAUST OXYGEN
02 SENSOR
1 CATALYTIC CONVERTER
45 0997-6E
Figure C2-1 Closed Loop System
MODES OF OPERATION
The ECM looks at voltages from several sensors to
determine how much fuel to give the engine.
The fuel
is delivered under one of several conditions,
called
"modes". All the modes are controlled by the E:CM.
and are described below.