1988 PONTIAC FIERO check engine

DRIVEABILITY AND EMISSIONS - 5.0L (VIN E) 6EZ-CZ-11
IDLE AIR CONTROL (IAC) VALVE
IAC VALVE GASKET
THROTTLE BODY ASSEMBLY
Figure C2-16 - Thread-Type IAC Valve
Install or Connect
1. TPS on throttle body assembly, while lining up
TPS lever with TPS drive lever on throttle body.
2. Two
TPS attaching screw assemblies.
Tighten
@ Screw assemblies to 2.0 N-m (18.0 in.lbs.).
3. Electrical connector.
4. Check for TPS output as follows: - Use an ALDL scanner to read TPS output
voltage.
- With ignition "ON" and engine stopped, TPS
voltage should be less than 1.25 volts. If more
than 1.25 volts, replace TPS.
IDLE AIR CONTROL (IAC) VALVE
Replacement (Figure CZ-16)
NOTICE:
The IAC valve is an electrical
component
and must not be soaked in any liquid
cleaner or solvent. Otherwise
damage
could result.
Important
All thread-mounted IAC valves on Model 220 TBI
units have a dual taper, 10 mm diameter, pintle.
Any replacement of an IAC valve must have the
correct part number with the appropriate pintle
taper and diameter for proper seating of the valve
in the throttle body.
Remove or Disconnect
1. Electrical connector.
2. IAC valve, using 32 mm (1-114") wrench.
3. IAC
valve gasket and discard.
Clean
@ Old gasket material from surface of throttle body
assembly to insure proper seal of new gasket.
NOTICE: If the IAC valve has been removed during
service, its operation may be tested
electrically with the
IACIISC Motor Tester
(Available Tool
# 5-37027, or BT-8256K).
However, if the valve pintle is extended
electrically, it must also be retracted
electrically. Under no circumstances
should the valve pintle be tampered with
by hand, screwed, or pushed in, or pulled
out, as damage could occur.
Important
No physical adjustment of the IAC valve assembly
is required after installation. The IAC valve is
reset by the ECM. When the vehicle is operated at
normal engine temperature at approximately 40
mph (64
kmlhr.), the ECM causes the valve pintle
to seat in the throttle body. The ECM then resets
the pintle to the correct position. Proper idle
regulation should result.
Install or Connect
1. IAC valve with new gasket into throttle body
NOTICE: New IAC valves that have been preset
at the factory should be installed in
the throttle
body in an "as is"
condition, without any adjustment.
Tighten
@ IAC valve assembly to 18.0 N.m (13.0 lb. ft.)
with 32 mm
(1-114") wrench.
2. Electrical connector to IAC valve.
3. Start engine and allow engine to reach operating
temperature.
Important
When the engine is turned "OFF," the IAC valve
will be reset by the ECM.
THROTTLE BODY ASSEMBLY
Replacement (Figure CZ-8)
NOTICE:
Procedures related to replacement of the
individual components below have been
described previously and should be
followed, or damage could occur.
Remove or Disconnect
1. Throttle body injection unit, described below
2. Fuel
meter body-to-throttle hodv attaching ~CI'PW
.i~~rmhlie

6E2-C2-12 DRIVEABILITY AND EMISSIONS - 5.0b (VIN E)
3. Fuel meter body assembly.
4. Throttle body-to-fuel meter body gasket. Discard
gasket.
a Disassemble
@ TPS from old throttle body, according to previous
instructions, for reuse on new throttle body. (New
IAC valve comes with new throttle body.)
Assemble
@ TPS onto replacement throttle body assembly,
according to previous instructions.
Install or Connect
1. New throttle body-to-fuel meter body gasket.
2. Fuel meter body assembly on throttle body
assembly.
3. Fuel meter body-throttle
body attaching screw
assemblies that have been coated with locking
compound.
Tighten
@ Attaching screw assemblies to 4.0 N.m
(35.0 Ib. in.).
4. TBI
unit onto engine, as described below.
MllMiMhlM IDLE SPEED CHECK
The idle stop screw, used in mechanically setting
minimum engine idle speed has been set at the factory
and should not require further adjustment. However,
to check that the setting is correct, proceed as follows:
I. Plug any vacuum ports, as required.
2. If present, remove idle stop screw plug by piercing
it with an awl, then applying leverage (Figure
C2-17).
3. Connect tachometer to engine.
4. With IAC valve connected, ground the diagnostic
terminal
(ALDL connector).
5.
Turn "ON" ignition, do not start engine. Wait at
least 45 seconds (this allows IAC valve pintle to
extend and seat in throttle body).
6. With ignition "ON," engine stopped, test terminal
still grounded, disconnect
IAC valve electrical
connector.
7, Remove ground from diagnostic terminal and
"startJ' engine. With transmission in neutral,
allow engine rpm to stabilize.
8. The tachometer should read 400 - 450 rpm. If not,
adjust the idle stop speed screw accordingly.
9. Turn ignition "OFF" and reconnect IAC valve
electrical connector.
10. Use silicon sealant or equivalent to cover
minimum idle adjustment screw hole.
11. Unplug any plugged vacuum ports.
1 BOLT - TIGHTEN TO 16 N,rn (12 FT. LBS.)
TBI UNIT
1 GASKET (MUST BE INSTALLED WITH STRIPE FACING UP) ENGINE INTAKE MANIFOLD
Figure C2-18 - Replacing TBI 220 Unit

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.

6E2-CZ-16 DRIVEABILITY AND EMISSIONS - 5.OL (WIN E)
CHART C-2C
IDLE AIR CONTROL (IAC) VALVE CHECK
5.OL (VIN E) "F'" SERIES (TBI)
Circuit Description:
The ECM controls idle rprn with the IAC valve. To increase idle rpm, the ECM moves the IAC valve out,
allowing more air to pass by the throttle plate. To decrease rpm, it moves the IAC valve in, reducing air flow by
the throttle plate. A "Scan" tool will read the
ECM commands to the IAC valve in counts.
The higher the
counts, the more air allowed (higher idle). The lower the counts, the less air allowed (lower idle).
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Continue with test, even if engine will not idle. If
idle is to low, "Scan" will display 80 or more
counts, or steps. If idle is high, it will display
"0"
counts. Occasionally, an erratic or unstable idle
may occur.
Engine speed may vary 200 rpm, or
more, up and down. Disconnect IAC. If the
condition is unchanged, the IAC is not at fault.
2. When the engine was stopped, the IAC Valve
retracted (more air) to a fixed "Park" position for
increased air flow and idle speed during the next
engine start. A "Scan" will display 100 or more
counts. When performing this test, immediately
note rprn on start up, because, on a warm engine,
the rprn will decrease rapidly.
3. Be sure to disconnect the IAC valve prior to this
test.
The test light will confirm the ECM signals
by
a steady or flashing light on all circuits.
4. There is a remote possibility that one of the
CKTs
is shorted to voltage, which would have been
indicated by a steady light. Disconnect ECM and
turn the ignition
"ON" and probe terminals to
check for this condition.
Diagnostic Aids:
A slow unstable idle may be caused by a system
problem that cannot be overcome by the
IAC. "Scan"
counts will be above 60 counts, if too low,
and "0"
counts, if engine speed is too high.
If idle is too high, stop engine. Ignition "Oh'".
Ground diagnostic terminal. Wait 30 seconds for
IAC to seat, then, disconnect IAC. Lnground
diagnostic terminal and start engine. If idle speed is
above 450 rprn in drive, locate and correct vacuum
leak. If rpm is less than 450 rpm,
ad,jrlst minimum
idle speed, or correct other conditions, which may
affect idle. refer to Rough Unstable or Incorrect Idle,
in Symptoms, Section
"R".
@ System too lean (Hi.gh AirJFuel Ratio)
Idle speed may be too high or too low. Engine
speed may vary up and down, disconnecting IAC
does not help. May set Code
33.
"Scan" and/or Voltmeter will read an oxygen
sensor output less than 300 mv
(.3 volts). Check
for low regulated fuel pressure or water in
fuel. A
lean exhaust, with an oxygen sensor outpirt fixed
above 800
mv (.8 volts), will be a contaminated
sensor, usually silicone. This may also set
a Code
45.
@ System too rich (Low AirIFuel Ratio)
Idle speed too low. "Scan" counts usually above
80. System obviously rich and may exhibit black
srnoke exhaust.
"Scan" tool and/or Voltmeter will
read an oxygen
sensor signal fixed above 800
mv (.8 volts).
Check:
- High fuel pressure
- Injector leaking or sticking
@ Throttle Body. Remove IAC and inspect bore for
foreign material or evidence of
IAC valve
dragging the bore.
@ If above ;
e all OK, refer to "Rough, Unstable,
Incorrect Idle or Stalling", in Symptoms, Section
"I<".

DRIVEABILITY AND EMISSIONS 5.8L (VIN E) 6EZ-C3-1
SECTION C3
EVAPORATIVE EMISSION CONTROL SVSEENI (EECS)
CONTENTS
........................ GENERAL DESCRIPTION ............... C3-1 DIAGNOSIS C3-2
.......... PURPOSE ........................ C3-1 VISUAL CHECK OF CANISTER C3-2
.......... VAPOR CANISTER.. ................. C3-1 CANISTER PURGE SOLENOID C3-2
................. EVAPORATIVE EMISSION SYSTEM.. ..... C3-1 ON-CAR SERVICE C3-2
............ IN-TANK PRESSURE CONTROL VALVE . . C3-2 FUEL VAPOR CANISTER R/R C3-2
.................. RESULTS OF INCORRECT OPERATION .... C3-2 CANISTER HOSES.. C3-2
................ PARTS INFORMATION C3-2
GENERAL DESCRIPTION
PURPOSE
The basic evaporative emission control system
(EECS) used on all vehicles is the charcoal canister
storage method. This method transfers fuel vapor
from the fuel tank to an activated carbon (charcoal)
storage device (canister) to hold the vapors when the
vehicle is not operating. When the engine is running,
the fuel vapor is purged from the carbon element by
intake air flow and consumed in the normal
combustion process.
VAPOR CANISTER
Gasoline vapors from the fuel tank flow into the
tube labeled tank. Any liquid
fuel goes into a
reservoir in the bottom of the canister to protect the
integrity of the carbon bed above (Figure C3-1). These
vapors are absorbed into the carbon. The canister is
purged when the engine is running above idle speed.
Ambient air is allowed into the canister through the
air tube in the top. The air mixes with the vapor and
the mixture is drawn into the intake manifold.
EVAPORATIVE EMISSION SYSTEM
The canister is equipped with a normally closed
(N/C) solenoid to control canister purge. The ECM
operates the solenoid which controls vacuum to the
purge valve in the charcoal canister. Under cold
engine or idle conditions, the solenoid is turned "OFF"
by the ECM, which closes the solenoid and blocks
vacuum to the canister purge valve.
The ECM turns "ON" the solenoid valve and allows
purge when:
@ Engine is warm.
@ After the engine has been running a specified
time.
@ Above a specified road speed.
@ Above a specified throttle opening.
TANKTUBE LQUID FUEL AREA
INLET AIR VAPOR STORAGE AREA
PURGE TUBE PURGE
SOLENOID
Figure C3-1 - Inverted Function Vapor Canister -
With Encapsulated Purge Solenoid
This is an ECM feedback system that increases
purge until the ECM senses a rich condition from the
oxygen sensor. The purge
is then regulated until the
ECM no longer receives a rich signal from the
O2
sensor. This system uses an in-tank pressure control
valve to control the flow of vapors from the fuel tank to
the canister.

6E2-C3-4 5.OL (VIN E) DRIVEABILITY AND EMISSIONS
428 DK GRNNEL
CHART C-3
CANlSTER PURGE VALVE CHECK
5.OL (VIN E) "F"' SERlES (TBI)
Circuit Description:
Canister purge is controlled by a solenoid that allows manifold vacuum to purge the canister when
energized. The ECM supplies a ground to energize the solenoid (purge "ON").
If the following conditions are met with the engine running, the purge solenoid is energized (purge "ON").
@ Engine run time after start more than 1 min.
@ Coolant temperature above 80°C.
Vehicle speed above
5 mph.
@ Throttle off idle. TPS signal about .75 volt.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
I. Checks to see if the solenoid is opened or closed.
The solenoid is energized in this step so it should
be open.
2. Completes functional check,
by grounding test
terminal. This should, normally, de-energize the
solenoid and allow the vacuum to drop (purge
"ON").
3. Checks for
a complete circuit. Normally, there is
battery voltage on CKT 39, and the ECM provides
a ground on CKT 428.
A shorted sole~oid could
cause an open circuit in the ECM.
Diagnostic Aids:
Normal operation of the canister purge solenoid is
described as follows:
With ignition "ON", engine stopped, diagnostic
terminal ungrounded, the purge solenoid will be
energized. With ignition "ON", engine "OFF", diagnostic
terminal grounded, the purge solenoid will be
de-energized.

DRIVEABILITY AND EMISSIONS 5.QL (VIN E) 6Ef-C4-1
SECTION C4
IGNITION SYSTEM 1 (EST)
CQN"FEB\BTO
GENERAL DESCRIPTION ............... C4-1
PURPOSE ........................ C4-1
OPERATION
............*......... C4-1
DIAGNOSIS
........................ C4-1
..... RESULTS OF INCORRECT EST OPER. C4-1
HOW CODE 42 IS DETERMINED ....... C4-2
GENERAL DESCRIPTION
PURPOSE
The High Energy Ignition (HE11 system controls
fuel combustion by providing a spark to ignite the
compressed
aidfuel mixture at the correct time. To
provide improved engine performance, fuel economy,
and control of exhaust emissions, the ECM controls
distributor spark advance (timing) with the Electronic
Spark Timing (EST) system.
Only the Electronic Spark 'Timing (EST) system
will be described here. Additional information on the
HE1 system is found in Section 6D.
OPERATION
The standard high energy ignition (HEI) system
(described in Section 6D) has a modified distributor
module, which is used in connection with EST.
The
module has eight terminals. (See Figure C4-1).
IGN. COIL TERMINALS
EST TERMINALS PICK-UP
COIL TERMINALS
Figure C4-1 - Distributor Module
To properly control ignition/combustion timing,
the ECM needs to know:
@ crankshaft position
@ engine speed (rpm)
@ engine load (manifold pressure or vacuum)
CODE12 ........................ C4-2
CHECKING EST PERFORMANCE ........ C4-2
ON-CAR SERVICE ...a.e.............. C4-2
SETTING TIMING
.................. C4-2
PARTSINFORMATION ................ C4-2
@ atmospheric (barometric) pressure
@ engine temperature
The EST system consists of the distributor
module, ECM, and connecting wires. The distributor
has four wires, from the
HE1 module, connected to the
ECM.
These circuits perform the following functions:
@ Distributor reference. Terminal "C"
This provides the ECM with rpm and crankshaft
position information.
@ Reference ground. Terminal "A"
'I'his wire is grounded in the distributor and
makes sure the ground circuit has no voltage drop
which could affect performance. If it is open, it
may cause poor performance.
@ Bypass. Terminal "BJ'
At about 400 rpm, the ECM applies 5 volts to this
circuit to switch spark timing control
from the
HE1 module to the ECM. An open or grounded
bypass circuit will set a Code 42 and the engine
will run at base timing, plus a small
amount of
advance built into the
HE1 module.
@ EST. 'Terminal "D"
After bypass voltage is applied, the ECM uses this
circuit to trigger the
HE1 module. The ECM uses
the distributor reference signal to base its
calculation of the amount of spark advance
needed, under present engine conditions.
Lf the
base timing of the engine is incorrect, the entire
spark curve will be incorrect.
RESULTS OF INCORRECT EST OPERATION
An open, or ground, in the EST circuit, will set a
Code 42 and cause the engine to run on the HE1
module timing. 'I'his will cause poor performance and
poor fuel economy.
'I'he ECM uses information from the MAP and
coolant sensors, in addition to rpm, to calculate spark
advance as follows.
I,ow MAP output voltage = More spark advance
Cold Engine
= More spark advance
High
MAP Output Voltage, = Less spark advance
IIot 12ngine = 1,ess spark advance

6E2-C4-2 5.8L (VIN E) DRIVEABILIW AND EMISSIONS
Therefore, detonation could be caused by low MAP
output or high resistance in the coolant sensor circuit.
Poor performance could be caused by high MAP
o~~tput or low resistance in the coolant sensor circuit.
HOW CODE 42 IS DETERMINED
When the system is running on the HE1 module,
that is, no voltage on the bypass line, the
HE1 module
grounds the EST signal. The ECM expects to see no
voltage on the EST line during this condition. If it
sees a voltage, it sets Code
42 and will not go into the
EST mode. When the rpm for EST is reached (about
400 rpm),
the ECM applies 5 volts to the bypass line and the EST
should no longer be grounded in the
HE1 module, so,
the EST voltage should be varying.
If the bypass line is open, the
HE1 module will not
switch to EST mode, so, the EST voltage will be low
and Code
42 will be set.
If the EST line is grounded, the HE1 module will
switch to EST but, because the line is grounded, there
will be no EST signal and the engine will not run. A
Code
42 may, or may not, be set.
The description, operation, and diagnosis of the
HE1 system are found in Section 6D of this manual.
This section will address diagnosis of that portion of
the Ignition System pertaining to the EST operation.
CODE 12
Code 12 is used during the Diagnostic Circuit
Check procedure to test the code display ability of the
ECM. This code indicates that the ECM is not
receiving the engine rpm (REFERENCE) signal. This
occurs with the ignition key
"ON" and the engine not
running.
The "Reference" signal, also, triggers the fuel
injection system. Without the "Reference" signal, the
engine cannot run.
ON-CAR SERVICE
SETTING TIMING
Set timing according to instructions on Vehicle
Emission Control Information label.
PARTS INFORMATION
PART NAME GROUP
....................... Module, Distr 2.383
......................... Coil, Distr 2.170