1988 PONTIAC FIERO check engine

DRIVEABILITYAND EMISSIONS 5.OL (VIN F) & 5.7L (V1N 8) 6E3-C3-9
SECTION C3
EVAPORATIVE EMlSSlON CONTROL SYSTEM (EECS)
CONTENTS
...................... ............... GENERAL DESCRIPTION C3-1 DIAGNOSIS .. C3-2
.......... PURPOSE ........................ C3-1 VISUAL CHECK OF CANISTER C3-2
VAPOR CANISTER .............. C3-1 FUNCTIONAL TEST
EVAPORATIVE EMISSION SYSTEM
...... C3-1 Vapor Canister Purge Valve ........ C3-2
..... FUEL TANK PRESSURE CONTROLVALVE . . C3-2 Tank Pressure Control Valve 63-2
IN-TANK PRESSURE CONTROL VALVE . . C3-2 ON-CAR SERVICE ................. C3-3
RESULTS OF INCORRECT OPERATION .... C3-2 FUEL VAPOR CANISTER ............ C3-3
CANISTERHOSES. ................... C3-3
................ PARTS INFORMATION C3-3
GENERAL DESGRIP"T0N
PURPOSE
The canister is equipped with a normally closed
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
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
TANK TUBE
INLET AIR
I PURGE TUBE
fl LIQUID FUEL AREA
a VAPOR STORAGE AREA
a PURGE SOLENOID
Fiqure C3-1 - Inverted Function Vapor Canister - - With Encapsulated Purge Solenoid

6E3-C3-2 5.OL (VIN F) & 5.7L (WIN 8) DRIVEABILITY AND EMISSIONS
The ECM turns "ON" the solenoid valve and allows
purge when:
@ Above a specified road speed.
r Engine is warm
@ After the engine has been running a specified
time.
@ Above a specified throttle opening.
This
is an ECM feedback system that increases
purge until the ECM senses a rich condition from the
O2 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.
IN-TANK PRESSURE CONTROL VALVE
The in-tank pressure control valve, a combination
roll-over, integral pressure and vacuum relief valve, is
located with the fuel sending unit in the fuel tank.
When vapor pressure in the tank exceeds
1" Hg (5
kPa) the valve opens and allows vapors to vent to the
canister and then be purged. When the tank pressure
drops below the opening point of the valve it will close,
keeping vapors in the fuel tank. The valve provides
vacuum relief to protect against vacuum build up in
the fuel tank and roll-over protection to prevent liquid
fuel from entering the canister during normal driving
maneuvers.
1 DIAPHRAGM
2 VENT RESTRICTION
3 CONTROL VACUUM TUBE
4 TUBE TO FUEL TANK 10-1-85 5 TUBE TO CANISTER *6s 2971-6~
RESULTS OF INCORRECT OPERATION
Poor idle, stalling and poor driveability can be
caused by:
- Inoperative purge solenoid
- Damaged canister
- Hoses split, cracked and, or not connected to
the proper tubes.
Evidence of fuel loss or fuel vapor odor can be
caused by:
- Liquid fuel leaking from fuel lines.
- Cracked or damaged canister
- Disconnected, misrouted, kinked, deteriorated
or damaged vapor hoses, or control hoses.
DIAGNOSIS
The canister purge solenoid operation is covered in
the charts at the end of this section.
VISUAL CHECK OF CANISTER
Cracked or damaged, replace canister.
FUNCTIONAL TEST
Vapor Canister Purge Valve
Apply a short length of hose to the lower tube of
purge valve, and atempt to blow through it. Little or
no air should pass into the canister.
(A small amount
of air will pass if the canister has a constant purge
hole). With hand vacuum pump, apply vacuum
(15" Hg
or 51 kPa) through the control valve tube (upper tube).
The diaphragm should hold vacuum for at least
20
seconds. If not the canister must be replaced. If the
diaphragm holds vacuum, again try to blow through
the hose connected to the lower tube while vacuum is
still being applied. An increased flow of air should be
observed. If not, the canister must be replaced.
Tank Pressure Control Valve
With a hand vacuum pump apply vacuum (15" or
51 kPa) to the control vacuum tube. The diaphragm
should hold vacuum for at least
20 seconds. If it does
not hold vacuum the diaphragm is leaking and the
valve must be replaced.
With the vacuum still applied to the control
vacuum tube, apply a short hose to the valve's tank
tube side, blow into the tube. You should feel the air
pass through the valve. If the air does not pass
through, the valve should be replaced.
Figure C3-2 Fuel Tank Pressure Control Valve

6E3-C3-4 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
428 DK GUNNEL
BULKHEAD
CHART
CANISTER PURGE SOLENOID CHECK
5.OL (VIN F) & 5.7L (VIN 8) ""FYSERIES (PORT)
Circuit Description:
Canister purge is controlled by a solenoid that allows manifold vacuum to purge the canister when de-
energized. The
ECM supplies a ground to energize the solenoid (purge "ON").
If the diagnostic test terminal is grounded, with the engine stopped, or the following conditions are met
with the engine running, the purge solenoid will be energized (purge "ON").
@ Engine run time after start more than 1 minute.
@ Coolant temperature above 75°C.
@ Vehicle speed above 15 mph.
@ Throttle position is above idle.
Test Description: Numbers below refer to circled 2. Grounding the diagnostic terminal will energize
numbers on the diagnostic chart. the solenoid and allow vacuum to pass.
1. The external vacuum source must be applied to 3. Some solenoids may have a large enough bleed
the purge solenoid at the canister. built into them to appear to be operating
incorrectly.

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-C4-1
SECTION C4
IGNIION SYSTEM 1 EST
..................... GENERAL DESCRIPTION ................ C4-1 ON-CAR SERVICE C4-2
.................. PURPOSE ......................... C4-1 SETTING TIMING.. C4-2
OPERATION ....................... C4-1 HOW CODE 42 IS DETERMINED.. ....... C4-2
................. RESULTS OF INCORRECT OPERATION .... C4-1 PARTS INFORMATION C4-2
DIAGNOSIS ......................... C4-1
CODE12.......................... C4-1
GENERAL DESCRIPTION
PURPOSE
The high energy ignition (HEI) system controls
fuel combustion by providing a spark to ignite the
compressed
airlfuel 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
FIE1 system is found in Section "6D".
To properly control ignitionlcombustion timing
the ECM needs to know:
e Crankshaft position
e Engine speed (rpm)
@ Mass Air Flow
@ Engine temperature
OPERATION
The EST system consists of the distributor
module, ECM, and connecting wires. The connector
terminals are lettered as shown in CHART C-4.
These circuits perform the following functions:
@ Distributor reference (CKT 430).
This provides the ECM with rpm and crankshaft
position information.
If the wire becomes open or
grounded the engine will not run, because the ECM
will not operate the injectors.
If the engine cranks hut
won't run, see CHART
A-3.
e Reference ground (CKT 453).
This 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.
@ Bvpass (CKT 424).
At about 400 rpm, the ECM applies
5 volts to this
circuit to switch spark timing control from the
I-IEI
module to the ECM. The wire goes through a
connector between the 4 wire connector and the ECM.
This is disconnected to the set hase timing. 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 (CKT 423). - This circuit triggers the HE1 module after the
engine is started and no Code 42 detected. The ECM
does not know what the actual timing is, but it does
know when it gets the reference signal. It then
advances or retards the spark from that point.
Therefore, if the base timing is set incorrectly, the
entire spark curve will be incorrect.
RESULTS OF INCORRECT OPERATION
An open or ground in the EST circuit will set u
Code 42 and cause the engine to run on the HE1
module timing. This will cause reduced performance
and poor fuel economy.
The ECM uses information from the
MAE' and
coolant sensors in addition to rpm to calculate spark
advance as follows:
e Cold engine = more spark advance.
r Engine under minimum load based on rpm
and low amount of air flow- more spark
advance. Hot engine
= less spark advance.
@ Engine under heavy load based on rpm and
high amount
of air flow- less spark advance.
DIAGNOSIS
The description, operation, and repair procedures
of the
HE1 system are found in Section "6D" of this
manual. For an ignition system check, refer to
CHART C-4 at the end of this section.
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.
'Phis occurs with
the ignition key
"ON", and the engine not running.

6E3-C4-2 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
The "Reference" signal also triggers the fuel
injection system. Without the "Reference" signal the
engine cannot run. This signal can be checked by
using
a "Scan" tool which will help determine the
cause of an engine that cranks but won't start.
OM-CAR SERVICE
SETTING TIMING
The initial base timing is set by disconnecting the
timing connector. Then set the timing to the
specification shown on emmision control information
label. This will cause Code 42 to be stored in the
memory of the ECM. The memory must be cleared
after setting timing.
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 or grounded, the
HE1
module will not switch to EST mode, so the EST
voltage will be low and Code 42 will be set.
PARTS INFORMATION
PART NAME GROUP
Coil, Distr ........................... 2.170
Controller, ECM
(Remanufactured)
................ 3.670
Distributor
.......................... 2.361
Module, Distr
........................ 2.383

6E3-C4-4 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
"C" /
DISTRIBUTOR CONNECTOR
CONNECTOR
430 PPLNVHT
424 TANIBLK
- - - GRY. CONN.
2-F3-87
7-27-87
SS 1356-6E
CHART C-4
IGNITION SYSTEM CHECK
(INTEGRAL COIL)
5.0b (VIN F) & 5.7L (VIN 8) "F" SERIES (PORT)
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Checks for proper output from the ignition system.
The spark tester requires a minimum of 25,000
volts to fire. This check can be used in case of an
ignition miss because the system may provide
enough voltage to run the engine but not enough
to fire a spark plug under heavy load.
IA. If spark occurs with EST connector disconnected,
pick-up coil output is too low for
EST operation.
2. Normal reading during cranking is about
8-10
volts.
3. Checks for a shorted module or grounded circuit
from the ignition coil to the module. The
distributor module should be turned
"OFF", so
normal voltage should be about 12 volts. If the
module is turned
"ON", the voltage would be low,
but above
1 volt. This could cause the ignition coil
to fail from excessive heat. With an open ignition
coil primary winding,
a small mount of voltage
will leak through the module from the battery to
the tach. terminal.
4. Checks the voltage output with the pick-up coil
triggering the module.
A spark indicates that the
ignition system has sufficient output, however,
intermittent no-starts or poor performance could
be the result of incorrect polarity between the
ignition coil and the pick-up coil
.
The color of the pick-up coil connector has to be
yellow, if one of the ignition coil leads is yellow. If
the ignition coil has a white lead, any pick-up coil
connector color, except yellow, is
OK.
5. Checks
for an open module or circuit to it. 12 volts
applied to the module
"P" terminal should turn
the module
"ON" and the voltage should drop to
about
7-9 volts.
6. This should turn "OFF" the module and cause a
spark. If no spark occurs, the fault is most likely
in the ignition coil, because most module problems
would have been found before this point in the
procedure.
A module tester could determine
which is at fault.

6E3-C5-4 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
CHART C-5
ELECTRONIC SPARK CONTROL
5.OL (VIN F) & 5.7L (VIN 8) ""F-ERIES (PORT)
Circuit Description:
Electronic spark control is accomplished with a module that sends a voltage signal to the ECM. As the
knock sensor detects engine knock, the voltage from the
ESC module to the ECM is shut "OFF" and this signals
the ECM to retard timing, if engine rpm is over about 900.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1.
If a Code 43 is not set, but a knock signal is
indicated while running at 1500 rpm, listen for an
internal engine noise. Under a no load condition,
there should not be any detonation, and if knock is
indicated, an internal engine problem may exist.
2. Usually a knock signal can be generated by
tapping on the right exhaust manifold. This test
can also be performed at idle. Test number
1 was
run at 1500 rpm to determine if a constant knock
signal was present, which would affect engine
performance.
3. This tests whether the knock signal is due to the
sensor,
a basic engine problem, or the ESC
module.
4. If the module ground circuit is faulty, the ESC
module will not function correctly. The test light
should light indicating the ground circuit is
OK.
5. Contacting CKT 496, with a test light to 12 volts,
should generate a knock signal to determine
whether the knock sensor is faulty, or the ESC
module can't recognize a knock signal.
Diagnostic Aids:
"Scan" tools have two positions to diagnose the
ESC system. The knock signal can be tnonitored to see
if the knock sensor is detecting a knock condition and
if the ESC module is functioning, knock signal should
display "YES", whenever detonation is present. The
knock retard position on the "Scan" displays the
amount of spark retard the ECM is commanding. The
ECM can retard the timing up to 'LO degrees.
If the ESC system checks
OK, but detonation is
the complaint, refer to
"Detonation/Spark Knock" in
Section
"B".

DRIVEABILITY AND EMISSIONS 5.0L (VIN F) & 5.7b (VIN 8) 6E3-C5-5
THIS CHART SHOULD BE USED AFTER ALL OTHER CAUSES OF SPARK KNOCK HAVE BEEN CHECKED. I.E., TIMING, EGR, ENGINE
TEMPERATURE OR EXCESSIVE ENGINE
NOISE,ETC. IF CODE 43 IS SET, USE THAT CHART FIRST.
@ "SCAN" TOOL SET ON KNOCK SIGNAL.
@ RECONNECT ESC MODULE.
DISCONNECT KNOCK SENSOR.
@ ENGINE IDLING.
MOMENTARILY TOUCH KNOCK SENSOR
HARNESS (CKT
496) WITH A TEST LIGHT TO 12V.