1988 PONTIAC FIERO relay

6EZ-C2-2 DRIVEABILITY AND EMISSIONS - 5.8b (VIN E)
1.5:1 at -36°C (-33°F) to 14.7:1, at 94°C (201°F)
running temperature.
The ECM controls the amount of fuel delivered in
the starting mode by changing how long the injector is
turned "ON" and "OFF". This
is done by "pulsing" the
injector for very short times.
Clear Flood Mode
If the engine floods, clear it by pushing the
accelerator pedal down all the way. The ECM then
pulses the injector at a
20:1 airlfuel ratio, and holds
this injector rate as long as the throttle stays wide
open, and the engine is below 600 rpm. If the throttle
position becomes less than
80%, the ECM returns to
the starting mode.
Run Mode
The run mode has two conditions called "Open
Loop" and "Closed Loop."
Open Loop
When the engine is first started, and it is above
400 rpm, the system goes into "Open Loop" operation.
In "Open Loop," the ECM ignores the signal from the
(02) sensor, and calculates the airlfuel ratio based on
inputs from the coolant temperature and MAP
sensors.
The system stays in "Open Loop" until the
following conditions are met:
1. The
O2 sensor has varying voltage output,
showing that it is hot enough to operate properly.
(This depends on temperature.)
2. The coolant temperature sensor is above a
specified temperature.
3. A specific amount of time has elapsed after
starting the engine.
Closed Loop
The specific values for the above conditions vary
with different engines, and are stored in the
programmable read only memory (PROM). When
these conditions are met, the system goes into "Closed
Loop" operation. In "Closed Loop," the ECM
calculates the
aidfuel ratio (injector on-time) based on
the signal from the
O2 sensor. This allows the aidfuel
ratio to stay very close to 14.7:1.
Acceleration Mode
The ECM looks at rapid changes in throttle
position and manifold pressure, and provides extra
fuel.
Deceleration Mode
When deceleration occurs, the fuel remaining in
the intake manifold can cause excessive emissions and
backfiring. Again, the ECM looks at changes in
throttle position and manifold pressure and reduces
the amount of fuel. When deceleration is very fast, the
ECM can cut off fuel completely for short periods.
Battery Voltage Correction Mode
When battery voltage is low,
the ECM can
compensate for a wealc spark delivered by the
distributor by:
@ Increasing injector on time of fuel delivered;
@ Increasing the idle rpm.
Fuel Cutoff Mode
No fuel is delivered by the injectors when the
ignition is "OFFJ'. This prevents dieseling. Also, fuel
is not delivered if no reference pulses are seen from
the distributor, which means the engine is not
running.
Fuel cutoff also occurs at high engine
rpm, to protect internal engine components from
damage.
FUEL CON"%ROL SYSXM
COMPONENTS
The fuel control system consists of the following:
@ Throttle body injection (TBI) unit
@ Fuel pump
Fuel pump relay.
FUEL PUMP AND
SENDING UNIT
FUEL SUPPLY LINE
16 FUEL RETURN LINE
Figure C2-2 - Fuel Control System

DRIVEABILITY AND EMlSSlONS - 5.0L (VIN E) 6E2-C2-3
BASIC SYSTEM OPERATION
The fuel control system (Figure C2-2) has an
electric fuel pump, located in the fuel tank with the
gage sending unit, which pumps fuel to the TBI
through the fuel supply line, then through an in-line
fuel filter. The pump is designed to provide
pressurized fuel at about 125
kPa (18 psi). A pressure
regulator in the TBI keeps fuel available to the
injectors at a constant pressure between 62 and 90
kPa (9 and 13 psi). Fuel in excess of injector need is
returned to the fuel tank by
a separate line.
The ECM controls the injectors that are located in
the fuel meter body assembly of the TBI. The injectors
deliver fuel in one of several modes, described above.
In order to properly control the fuel supply, the
fuel pump is operated by the ECM through the fuel
pump relay and oil pressure switch (see "Fuel Pump
Electrical Circuit").
THROTTLE BODY INJECTION (TBI) UNIT
The Model 220 unit (Figure C2-3) consists of three
major casting assemblies:
1. A fuel meter cover with:
A pressure regulator
2.
A fuel meter body with:
@ Two fuel injectors
3. A throttle body with:
@ Two throttle valves
@ An idle air control (IAC) valve
@ A throttle position sensor (TPS).
Fuel Injectors
Fuel injectors (Figure C2-4) are solenoid-operated
devices controlled by the ECM. The ECM turns on the
solenoid, which lifts a normally closed ball valve off a
seat. Fuel, under pressure, is injected in a conical
spray pattern at the walls of
the throttle body bore
above the throttle valve. The fuel which is not used by
the injectors passes through the pressure regulator
before being returned to the fuel tank.
A fuel injector which does not open may cause a
no-start condition. An injector which is stuck partly
open will cause a loss of pressure after setting, so long
crank times would be noticed. Also, dieseling could
occur because some fuel would be delivered to the
engine after the key is turned "OFF."
2 THROTTLE BODY ASSEMBLY
THROTTLE POSITION SENSOR (TPS)
IDLE AIR CONTROL (IAC) VALVE ASSEMBLY
FUEL METER BODY ASSEMBLY
FUEL METER COVER ASSEMBLY
8~ 0922 AS 115R7
PRESSURE REGULATOR
FUEL INJECTOR
1 FUEL INJECTOR INLET FILTER
THROTTLE BODY ASSEMBLY
FUEL FROM PUMP
INJECTOR ELECTRICAL TERMINALS
[ CONSTANT BLEED - (SOME MODELS) - PRESSURE REGULATOR DIAPHRAGM ASSEMBLY
PRESSURE REGULATOR SPRING
FUEL RETURN TO TANK
THROTTLE
VAWE
Figure C2-4 - TBI 220 Unit Operation
controlling the flow in the return line (by means of a
calibrated bypass).
The pressure regulator is serviced as part
of the
fuel meter cover and should not be disasembled.
Pressure Regulator If the pressure regulator in the TBI supplies
pressure which
is too low (below 62 kPa or 9 psi), poor
The pressure regulator (see Figure
C2-4) is a performance could result. if the pressure is too high,
diaphragm-operated relief valve with injector excess emissions and unpleasant exhaust odor
may
pressure on one side and air cleaner pressure on the
result.
other. The function of the regulator is to maintain
'1
constant pressure at the in.jecto1.s at ill1 times, by

DRIVEABILITY AND EMISSIONS - 5.OL (\/IN El 6EZ-CZ-5
sent to the ECM. The ECM then increases the injector
base pulse width, permitting increased fuel flow.
As the throttle valve rotates in response to
movement of the accelerator pedal, the throttle shaft
transfers this rotational movement to the
'I'PS. A
potentiometer (variable resistor) within the TPS
assembly changes its resistance (and voltage drop) in
proportion to throttle movement.
By applying a reference voltage (5.0 volts) to the
TPS input, a varying voltage (reflecting throttle
position) is available at the TPS output. For example,
approximately 2.5 volts results from a 50% throttle
valve opening (depending on TPS calibration). The
voltage output from the TPS assembly is routed to the
ECM for use in determining throttle position.
FUEL PUMP
The fuel pump is a turbine type, low pressure
electric pump, mounted in the fuel tank. Fuel
is
pumped at a positive pressure (above 62
kPa or 9 psi)
from the fuel pump through the in-line filter to the
pressure regulator in the TBI assembly Excess
fuel is
returned to the fuel tank through the fuel return line.
The fuel pump is attached to the fuel gage sender
assembly. A fuel strainer is attached to the fuel pump
inlet line and prevents dirt particles from entering the
fuel line and tends to separate
water from the fuel
Vapor lock problems are reduced when using an
electric
pump because the fuel is pushed from the tank
under pressure rather than being pulled
under
vacuum, a condition that produces vapor.
An inoperative fuel pump would cause
a. no start
condition. A fuel pump which does not provide enough
pressure can result in poor performance. (See "Fuel
System Pressure Test" procedure).
FUEL PUMP ELECTRICAL CIRCUIT
When the key is first turned "ON" without the
engine running, the ECM turns the
Fuel pump relay
"ON" for two seconds. This builds
up the fuel pressure
quickly. If the engine is not started within two
seconds, the
ECM shuts the fuel pump "OFF" and
waits until the engine starts. As soon as the engine is
cranked, the ECM turns the relay
"ON" and runs the
fuel pump.
As a backup system to the fuel pump relay, the
fuel pump can also be turned on
by the oil pressure
switch. The oil pressure sender has two circuits
internally. One operates the oil pressure indicator or
gage in the instrument cluster,
itnd the other is
anormally open switch which closes when oil pressure
reaches about 28
kPa (4 psi). If the fuel pump relay
fails, the oil pressure switch will run the fuel pump. An
inoperative fuel pump relay can result in long
cranking times, particularly if the engine is cold. The
oil pressure switch will turn on the fuel pump as soon
as oil pressure
reaches about 28 kPa (4 psi).
FUEL CONTROL
Always start with the "Diagnostic Circuit Check"
in Section
"6E2-A". This will reduce diagnosis time
and prevents unnecessary replacement of parts. The
information in this check will direct diagnosis
concerning "Engine
Crunlis But Won't Run" and the
"Fuel Control System," Section
"6E2-C2", including
diagnosis of an injector, pressure regulator,
fuel pump,
fuel
pump relay, and oil pressure switch.
Idle Air Control (IAC) Valve
A "Scan" tool reads IAC position in steps, calletl
"Counts." "0" steps indicates the ECM is commanding
the
IAC to be driven in, to a fully seiltetl position
(minimum idle air).
The higher the number steps, the
more idle air being allowed to pass
by the IAC valve.
cnose Refer to CHART C-2C for information to cliil,
the function of the IAC valve.
Driva bility
Refer to Section "B" for driveability symptoms
related to the fuel control.
ON-VEHICLE SERVICE
GENERAL SEWVICE INFORMATION
CAUTION:
e To prevent personal injury or damage to the
vehicle
as the result sf an accidental start,
disconnect and reconnect the negative
battery cable before and after service is
performed.
@ Also, catch any fuel that leaks out when
disconnecting the fuel lines, by covering the
fittings with
a shop cloth. Place the cloth in
an approved container when work is
complete.
The 'FBI unit repair procedures cover component
replacement with the unit on the vehicle,
tIowever,
throttle body replacement requires that the complete
unit
be removed from the enginc.

DRIVEABILITY AND EMISSIONS - S.0L (VIN E) 6EZ-C2-13
"THROTTLE BODY INJECTION (TBI) UNIT
Replacement (Figure C2-18)
a Remove or Disconnect
1. THERMAC hose from engine fitting.
2. Electrical connectors to IAC valve, TPS and fuel
injectors.
3. Grommet with wires from throttle body.
4. Throttle linkage, return
spring(s) transmission
control cable and cruise control (wherever
applicable).
5. Vacuum hoses (noting position of hoses) and
bracket.
6. Fuel inlet and return lines (use back-up wrench
J-29698-A or BT-8251-A). Discard o-
rings from
nuts.
7. TBI mounting hardware.
8. TBI flange (manifold mounting) gasket and
discard.
NOTICE: Stuff manifold opening with a rag to
prevent material from entering
engine, and remove old gasket
material from surface of intake
manifold.
Inspect
@ Intake manifold bore for loose parts and foreign
material, etc.
@ Intake manifold sealing surface for cleanliness.
Install or Connect
1. New TBI flange (manifold mounting) gasket.
2.
TI31 with mounting hardware.
Tighten
@ Hardwareto, 16.5N-m( 12Ib. ft.).
3. New o-rings on fuel line nuts
4. Fuel inlet and outlet lines.
Tighten - @ To 23 N.m (17 lb. ft.). (Use back-up wrench
J-29698-A or BT-8251-A to keep TBI nuts
from turning.)
5. Vacuum hoses and bracket.
6. Throttle linkage, return
spring(s) transmission
control cable and cruise control (wherever
applicable).
7. Grommet with wire harness to throttle body.
8. Electrical connectors, making sure connectors are
fully seated and latched.
9. Check to see if accelerator pedal is free by
depressing pedal to the floor
and releasing while
engine is "OFF".
10. With engine "OFF," and ignition "ON," check for
leaks around fuel line nuts.
11. Start engine and check for fuel leaks.
FUEL HOSEIPIPE ASSEMBLIES
Materials
Fuel Lines. These are welded steel tubes, meeting GM
Specification 124-M, or its equivalent. The fuel feed
line is
318" diameter, and the fuel return line is 5/16"
diameter. Do not use copper or aluminum tubing to
replace steel tubing. Those materials do not have
satisfactory durability to withstand normal vehicle
vibr, ii t' lon.
Clamps. These are stainless steel, screw band type
clamps,
#249472, or equivalent.
Coupled Hose. These are not to be repaired and are
replaced
&as an assembly.
Uncoupled Hose. Use only reinforced fuel resistant
hose, made of "fluroelastomer" material.
[lo not use w
hose within 4 inches (100 mm) of any part of the
exhaust system, or within 10 inches
(254 mm) of the
catalytic converter. The hose's inside diameter nus st
match the outside diameter of the steel tubing.
Fuel Line Repair
1. Cut
a piece of fuel hose 4 inches (100 mm) longer
than the section of line to be removed. If
more
than 6 inches (152 tnm) is to be removed, use a .
combination of steel pipe and hose. The
hose
length should not be more than 10 inches total.
2. Cut a section of pipe to be replacccl, with a tube
cutter. C'se the first step of a double flaring tool to
form a bead on the ends
of the pipe and also, on the
new section of pipe, if used.
3. Slide
the hose
clanlps onto the pip2 and push the
hose
2 inches (51 mm) onto each portion of the fuel
pipe. Tighten a
clamp on each side of the repair.
4. Secure
fuel line to the frame.
FUEL PUMP RELAY
(Figure
CZ-19)
The fuel pump relay is mounted in the engine
compartment. Other than checking for loose
connectors, the only service possible is replacement.
OIL PRESSURE SWITCH
(Figure C2-20)
The oil pressure switch is li~ounted on the engine.
This switch is a parallel power supply, with the fuel
pump relay, and will provide battery voltage to the
fuel
pump, after approximately 28 kPa (4 psi) oil
pressure is reached.

SWITCH ASM
Figure C2-20 - Oil Pressure Switch
PART D INFORMA"F0N
PART NAME GROUP
Meter Kit, Fuel. . . . . . . . . . . . . . . . . . . . . . 3.734
Injector Kit, Fuel. . . . . . , . . . . . . . . . . . . . 3.774
Pump, Fuel (In Tank). . . . . . . . . . . . . . . . . 3.900
Relay, Fuel Pump. . . . . . . . , . . . . . . . . . . . 3.900
Switch, Oil Press. . . . . . . . . . . . . . . . . . . . . 1.800
Throttle Body Injection Unit. . . . . . . . . . . . 3.725
Control Kit, Idle Air Valve. . . . . . . . . . . . . . 3.820

6EZ-C8-4 DRIVEABILITY AND EMISSIONS - 5.OL (VIN E)
I5 WAY (FRONT VIEW)
SPEED INPUT
4rH GEAR SIGNAL
422 TANIBLK
ALDL CONNECTOR
CHART C-8A
TRANSMISSION CONVERTER CLUTCH (TCC)
ELECTRICAL DIAGNOSIS
(Page 1 of 2)
5.OL (VIN E) "F" "SERIES (TBI)
Circuit Description:
The purpose of the automatic transmission torque converter clutch is to eliminate the power loss of the
torque converter, when the vehicle is in a cruise condition. This allows the convenience of the automatic
transmission and the fuel economy of a manual transmission.
Fused battery ignition is supplied to the TCC solenoid through the brake switch. the ECM will engage
TCC
by grounding CKT 422 to energize the solenoid.
TCC will engage when:
- Vehicle speed above 24 mph - Engine at normal operating temperature (above 70°C, 156°F)
- Throttle position sensor output not changing, indicating a steady road speed
- Brake switch closed
Test Description: Numbers below refer to circled solenoids
and relays before installing a
numbers on the diagnostic chart. replacement ECM. Replace
any solenoid or relay
1. Confirms 12 volt supply as well as continuity of that
measures less than 20 ohms.
TCC circuit.
2. Grounding the diagnostic terminal with engine Diagnostic Aids:
"OFF", should energize the capability of the ECM An
engine coolant thermostat that is stuck open or
to control the solenoid. opens
at too low a temperature, may result in an
3. Solenoid coil resistance must measure more than inoperative TCC.
20 ohms. Less resistance will cause early failure
of the ECM
drive^.". Using an ohmmeter, check
the solenoid coil resistance of
all ECM controlled

INDEX
SECTION PACE
....................... Detonation... B-4
.................. Diagnostic Procedure 2-5
................ Diagnostic Circuit Check A-8
..................... Dieseling. Run On B-6
Distributor Reference Signal
................. General Description C1-4
......................... Diagnosis C1-5
E
.................... ECM Terminals ... A-6
.................. ECM Wiring Diagram A3-A6
..................... EGR Control Valve C7-1
................. Valve Identification C7-2
................... Diagnosis. Service C7-2
EGR Control Solenoid
.................. C7-3
Parts Information
................... C7-3
......................... EGR Check C7-4
Electronic Control Module
................. General Description C1-I
......................... Diagnosis C1-5
............................ Service C1-6
..................... Function Check C1-6
Electronic Spark Control (ESC) System
................. General Description C5-1
................... Diagnosis. Service C5-I
Engine Coolant Temperature Sensor
................. General Description C1-2
......................... Diagnosis C1-5
Engine Cranks But Won't Run
............ A-14
........................ Engine Knock C5-4
.......................... ESC Module C5-1
.......................... ESC Sensor C5-1
..................... ESC System Check C5-4
ESTIlgnition System ................... C4-1
Evaporative Emission
Conirol System
General Description
................. C3-1
.......................... Diagnosis C3-2
Exhaust Emissions Excessive (Odors)
....... B-7
Exhaust Gas Recirculation (EGR) System
..... C7-1
Exhaust System Check Restricted
......... B-8
Fuel Control System
General Description
................. C2-1
Diagnosis. Parts Information
........... C2-6
Fuel Cutoff Mode
.................... C2-2
Fuel Meter Body Assembly
.............. C2- 1 I
Fuel Injectors ........................ C2-3
Fuel Meter Cover Assembly
.............. C2-8
Fuel Pressure Connection Assy
............ C2- 10
SECTION PAGE
........... Fuel Pressure Relief Procedure C2-6
.............. Fuel Pump Electrical Circuit C2-5
...................... Fuel Pump Relay C2-15
.................. Fuel System Diagnosis A- 18
............... Fuel System Pressure Test C2-7
......... Fuel Tank Pressure Control Valve C3-3
................... Fuel
Vapor Canister C3-3
G
.................. General Information 2-5
H
.......................... Hard Start B-2
.......... HE1 High Energy Ignition System C4-1
.......................... Hesitation
B-4
............ ldle Air Control System Check
.................. ldle Air Control Valve
......................... Diagnosis
....................... Service (EST)
Ignition System
................. General Descr~ption
......................... Diagnosis
Check
............................
........................ Incorrect ldle
.................. lnformation Sensors
................... Injector Balance Test
........................ Intermittents
......................... Introduction
Knock Sensor
................. General Description C1-4
......................... Diagnosis C1-6
....................... Lack Of Power B-3
Light. Manual Transmission Shift
......... C8-8
Light. Service Engine Soon
.............. A-10
Manual Transmission Electrical Diagnosis
... C8-10
Manual Transmission Overdrive Relay ..... C8-3
MAP Sensor
General Description
................. C1-2

FUNCTIONAL CHECKS/
DIAGNOSTIC CHARTS
2.8L (VIN S)
ECM QDR Check
......................... Chart C-1 C1-10
ParkINeutral Switch
......................... Chart C-1A C1-12
Power Steering Pressure Switch Check
........................ ChartC-1E C1-14
Injector Balance Test
........................ Chart C-2A C2-18
Idle Air Control
........................ Chart C-2C C2-20
Canister Purge Valve Check
......................... Chart C-3 C3-4
Ignition System Check
........................ Chart C-4A C4-4
Electr~c Control (Divert) -(Manual Transmission)
......................... Chart C-6 C6-6
Exhaust Gas Recirculation Check
........................ Chart C-7 C7-6
Automatic Transmission
Converter Clutch (TCC)
. (I of 2)
........................ Chart C-8 C8-2
Transmiss~on Converter Clutch
(TCC) Electrical Diagnosis
. (2 of 2)
........................ Chart C-8 C8-4
A/C Clutch Control
........................ Chart C-10 C10-2
Cooling Fan Control Circuit (I of 2)
........................ Chart C-12 C12-2
Cooling Fan Control Circuit (2 of 2)
........................ Chart C-12 C12-4
ParklNeutral Switch (Auto Only) ...... C1-4
AIC "ON" Signal .................. C1-4
Distributor Reference Signal ......... C1-4
......................... DIAGNOSIS C1-4
............................. ECM C1-4
........................... PROM C1-4
...................... ECM Inputs C1-5
Coolant Temp . Sensor ............. C1-5
..................... MAFSensor C1-5
..................... MAT Sensor C1-5
....................... 02Sensor C1-5
TPS ............................ C1-5
........................... VSS C1-5
...................... PIN Switch C1-5
................ A/C Request Signal C1-5
Power Steering Pressure Switch ...... C1-5
................. Reference Signal C1-5
ON-CAR SERVICE ..................... C1-5
ELECTRONIC CONTROL MODULE (ECM) . . C1-5
ECM & COMPONENTS REPLACEMENT
..................... PROM OR ECM C1-6
................. Functional Check C1-7
CALPAK .......................... C1-7
COOLANT SENSOR .................. C1-7
MAFSENSOR ...................... C1-7
MAF SENSOR POWER & BURN-OFF RELAY . C1-7
................... OXYGEN SENSOR C1-8
Throttle Position Sensor ............ C1-8
PARKINEUTRALSWITCH .............. C1-9
................. PARTS INFORMATION C1-9
ECM QDR Check
................... ... Chart C-1 ... C1-10
ParktNeutral Switch
........................ ChartC-1A C1-12
Power Steering Pressure Switch Check
........................ SECTION C . COMPONENT SYSTEMS ChartC-lE C1-14
2.8L (VIN S) SECTION C2 . 2.8L (WIN S)
FUEL CONTROL SYSTEM
................ 'Table of Contents .................... C-1 GENERAL DESCRIPTION C2-1
SECTION
C1 . 2.8L (VIN S)
ELECTRONIC CONTROL MODULE (ECM)
& SENSORS
ELECTRONIC CONTROL MODULE (ECM) ... C1-1
........................ ECM TYPES C1-1
........................... PROM C1-1
CALPAK .......................... C1-2
.................... ECM Function C1-2
............. INFORMATION SENSORS C1-2
Engine Coolant Temp . Sensor ........ C1-2
Mass Air Flow (MAF) Sensor ......... C1-2
.................. A/C MAF Sensor Cl-2
Manifold Air Temp . (MAT) Sensor ..... C1-2
Oxygen (Oz)Sensor ............... C1-3
Throttle Position Sensor (TPS) ........ C1-3
Vehicle Speed Sensor .............. C1-3
ParkINeutral Switch (Auto Only) ...... C1-4
......................... PURPOSE C2-1
.............. MODES OF OPERATION C2-1
................... Starting Mode C2-2
................. Clear Flood Mode C2-2
...................... Run Mode C2-2
................ Acceleration Mode C2-2
............... Deceleration Mode C2-2
Battery Voltage Correction Mode ..... C2-2
................. Fuel Cutoff Mode C2-3
Fuel Control System Components ..... C2-3
Basic System Operat~on ............. C2-3
THROTTLEBODY UNIT ............... C2-3
......................... FUELRAIL C2-3
..................... FUEL INJECTOR C2-3
............... PRESSURE REGULATOR C2-3
IDLE AIR CONTROL (IAC) VALVE ........ C2-4