1988 PONTIAC FIERO Service Repair Manual

6E3-C2-18 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
CHART C-2A
INJECTOR BALANCE TEST
The injector balance tester is a tool used to turn the injector on for a precise
amount of time, thus spraying a measured amount of fuel into the manifold.
This causes a drop in fuel rail pressure that we can record and compare between
each injector. All injectors should have the same amount of pressure drop
( k 10
kpa). Any injector with a pressure drop that is 10 kpa (or more) greater or less
than the average drop of the other injectors should be considered faulty and
replaced.
Engine "cool down" period
(10 minutes) is necessary to avoid irregular
readings due to "Hot Soak" fuel boiling. With ignition
"OFF" connect fuel gauge
5347301 or equivalent to fuel pressure tap. Wrap a shop towel around fitting
while connecting gage to avoid fuel spillage.
Disconnect harness connectors at all injectors, and connect injector tester
J-
34730-3, or equivalent, to one injector. On Turbo equipped engines, use adaptor
harness furnished with injector tester to energize injectors that are not
accessible. Follow manufacturers instructions for use of adaptor harness.
Ignition must be
"OFF" at least 10 seconds to complete ECM shutdown cycle.
Fuel pump should run about
2 seconds after ignition is turned "ON". At this
point, insert clear tubing attached to vent valve into a suitable container and
bleed air from gauge and hose to insure accurate gauge operation. Repeat this
step until all air is bled from gauge.
STEP 2
Turn ignition "OFF" for 10 seconds and then "ON" again to get fuel pressure
to its maximum. Record this initial pressure reading. Energize tester one time
and note pressure drop at its lowest point (Disregard any slight pressure
increase after drop hits low point.). By subtracting this second pressure reading
from the initial pressure, we have the actual amount of injector pressure drop.
STEP 3
Repeat step 2 on each injector and compare the amount of drop. Usually, good
injectors will have virtually the same drop. Retest any injector that has
a
pressure difference of lOkPa, either more or less than the average of the other
injectors on the engine. Replace any injector that also fails the retest. If the
pressure drop of all injectors is within
lOkPa of this average, the injectors
appear to be flowing properly. Reconnect
them and review "Symptoms," Section
"B".
NOTE: The entire test should not be repeated more than once without
running the engine to prevent flooding. (This includes any retest on
fa ulty injectors).

DRIVEABILITY AND EMISSIONS 2.8L (VIN 5) 6E3-C2-19
NOTE: If injectors are suspected of being dirty, they should be CHART C-2A
cleaned using an approved tool and procedure prior to
performing
this test. The fuel pressure test in Section A,
Chart A-7, should be completed prior to this test.
Step 1. If engine is at operating temperature, allow a 10 minute "cool down" period then connect
fuel pressure gauge and injector tester.
1. lgnition "OFF".
2. Connect fuel pressure gauge and injector tester.
3. lgnition "ON".
4. Bleed off air in gauge. Repeat until all air is bled from gauge.
Step
2. Run test:
1. lgnition "OFF" for 10 seconds.
2. lgnition "ON". Record gauge pressure. (Pressure must hold steady, if not see the Fuel
System diagnosis, Chart
A-7, in Section A).
3. Turn injector on, by depressing button on injector tester, and note pressure at the
instant the gauge needle stops.
1. Repeat step 2 on all injectors and record pressure drop on each.
Retest injectors that appear faulty (Any injectors that have a
10 kPa difference, either

6E3-C2-20 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
AIR THROTTLE FLOW BODY
LD START VALVE
8-5 BLUNVHT
BLUIBLK
GRMNVHT
. GRNIBLK
ECM
.
IAC COIL
"A" HI
IAC COIL "A" LO
IAC COIL "B" HI
C3 IAC COIL "B" LO
7-1 6-87
55 1800-6E
CHART C-2C
IDLE AIR CONTROL
2.8L (VIN S) ""F-SERIES (PORT)
Circuit Description:
The ECM will control engine idle speed by moving the IAC valve to control air flow around the throttle
plate. It does this by sending voltage pulses to the proper motor winding for each IAC motor. This will cause
the motor shaft and valve to move in or out of the motor a given distance for each pulse received. ECM pulses
are referred to as "counts".
@ To increase idle speed - ECM will send enough counts to retract the IAC valve and allow more air to flow
through the idle air passage and bypass the throttle plate until idle speed reaches the proper RPM. This
will increase the ECM counts.
@ To decrease idle speed - ECM will send enough counts to extend the IAC valve and reduce air flow through
the idle passage around the throttle plate. This will reduce the ECM counts.
Each time the engine is started and then the ignition is turned "OFF" the ECM will reset the IAC valve.
This is done by sending enough counts to seat the valve. The fully seated valve is the ECM reference zero. A
given number of counts are then issued to open the valve, and normal ECM control of IAC will begin from this
point. The
number of counts are then calculated by the ECM. This is how the ECM knows what the motor
position is for
a given idle speed.
The ECM uses the following information to control idle speed.
@ Battery voltage @ Engine Speed
@ Coolant Temperature @ A/C clutch signal
@ Throttle Position Sensor
Don't apply battery voltage across the IAC motor terminals. It will permanently damage the IAC motor
windings.
Test Description: Numbers below refer to circled Engine
idle speed can be adversely affected by the
numbers on the diagnostic chart. following:
1. Continue
with test even if engine will not idle. If @ ParUNeutral Switch - If ECM thinks the car is
idle is too low, "Scan" will display
80 or more always
in neutral, then idle will not be controlled
counts, or steps. If idle is high it will display
"0" to the specified rpm when in drive range.
counts.
@ Leaking injector(s) will cause fuel imbalance and
Occasionally an erratic or unstable idle may poor
idle quality due to excess fuel. See CHART
occur. Engine speed may vary
200 rpm or more up A-7.
and down. Disconnect
EAC. If the condition is @ Vacuum or crankcase leaks can affect idle.
unchanged, the IAC is not at fault. There is
a @ When the throttle shaft or throttle position sensor
system problem. Proceed to diagnostic aids below. is
binding or sticking in an open throttle position,
2. When the engine was stopped, the IAC valve the
ECM does not know if the vehicle has stopped
retracted (more air) to a fixed "Park" position for and does not control idle.
increased air flow and idle speed during the next
@ Check AIR management system for intermittent
engine start. A "Scan" will display
140 or more air
to ports while in "Closed Loop".
counts. @ In addition to electrical control of EGR, be sure to
3. Be sure to disconnect the IAC valve prior to this examine the
EGR valve for proper seating.
test. The test light will confirm the ECM signals @ Faulty battery cables can result in voltage
by a steady or flashing light on all circuits. variations. The
ECM will try to compensate,
4. There is a remote possibility that one of the CKTs which results in erratic idle speeds.
is shorted to voltage which would have been @ The ECM will compensate for A/C compressor
indicated by a steady light. Disconnect ECM and clutch
loads. Loss of this signal would be most
turn the Ignition "ON" and probe terminals to apparent
in neutral.
check for this condition.
@ Contaminated fuel can adversely affect idle. @ Perform in Diagnostic Aids: If all OK, refer to "Rough, Unstable, Incorrect Idle
or Stalling" "Svmptoms" in Section "B".

DRIVEABILITY AND EMISSIONS Z.$b (VIN S) 6E3-CZ-21
OPERATING TEMPERATURE.

6E3-CZ-22 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
BLANK

DRIVEABILITY AND EMISSIONS 2.8L (VIN 5) 6E3-C3-1
SECTION C3
EVAPORATIVE EMlSSlON CON"TOL SYSTEM (EECS)
CONTENTS
GENERAL DESCRIPTION ............... C3-1 DIAGNOSIS ........................ C3-2
PURPOSE ........................ C3-1 VISUAL CHECK OF CANISTER .......... 63-2
VAPOR CANISTER ................... C3-1 FUNCTIONAL TEST
EVAPORATIVE EMISSION SYSTEM
...... C3-1 Vapor Canister Purge Valve ........ C3-2
TANK PRESSURE CONTROLVALVE ...... C3-2 Fuel Tank Pressure Control Valve ..... C3-2
RESULTS OF INCORRECT OPERATION .... C3-2 ON-CAR SERVICE .......*+........ C3-3
FUEL VAPOR CANISTER R/R ............ C3-3
FUEL VAPOR CANISTER SOLENOID RIR.. .. C3-3
CANISTERHOSES.................... C3-3
................ PARTS INFORMATION C3-3
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
The canister used on these engines has a
diaphragm operated purge valve and a solenoid to
control purge (See Figure
C3-I). When the engine is
running, ported manifold vacuum is supplied to the
top of the
purge valve (Control Vacuum Signal) which
lifts the valve
diaphragm and opens the valve when
the throttle is above a specified opening.
The lower
tube on the purge
valve (PCV tube) is connected to the
solenoid valve.
EVAPORATIVE EMISSION SYSTEM
Under cold engine or idle conditions, the solenoid
is turned
"ON" by the ECM, which closes the purge
passage preventing canister purge.
'L'he ECM turns
"OFF" the solenoid valve and allows purge when the
following occur:
- 'I'he engine is warm.
- After the engine has been running a specified
length of time.
- 'I'he vehicle is above a specified road speed.
- Throttle valve is past a specified opening.
I CONTROL VAC Ifj VACUUM FROM TUBE #6
SOLENOID [ZI MANIFOLD VACUUM
a VAPOR FROM FUEL a SOLENOID VACUUM
TANK
"6s 2733-6E
Fiqure C3-1 - Vapor Canister
with Non-~nca~silated Solenoid

6E3-C3-2 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
The "CONTROL VAC" tube on the purge valve of the
canister is connected to a ported vacuum source.
When the engine is above idle speed, sufficient
vacuum is available to open the purge valve
diaphragm. Vapors are purge through the solenoid to
the combustion chamber.
This system also has a Tank Pressure Control
Valve to control the flow of vapors to the canister.
TANK PRESSURE CONTROL VALVE
The Fuel Tank Pressure Control Valve (Figure
C3-3) is located near the canister and is connected to
the fuel tank vapor line. When the engine is running,
manifold vacuum is supplied to the control vacuum
tube and the valve is opened allowing
fuel vapors too
vent to the canister. When the engine is "OFF", the
valve closes and vapors tend to remain in the tank.
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, or fuel
pump.
- 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. A failure in the
solenoid or connections may result in a Code
26.
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
1 DIAPHRAGM
2 VENT RESTRBCBIQN
3 CONTROL VACUUM TUBE
4 TUBE TO FUEL TANK 10-1-85 5 TUBE TO CANISTER *6s 2971-6~
Figure C3-3 Fuel Tank Pressure Control Valve
of air will pass if the canister has a constant purge
hole). With hand vacuum pump, apply vacuum
(15"E-Ig.
or 51 kPa) through the control valve tube (upper tube).
'I'he diaphragm should hold vacuum for at least 20
seconds. If not the canister must be replaced. If the
diaphragm holds
vacuu111, 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
shoi~ld hold vacuum for at least 20 seconds. If it does
not hold vacuum the
cliaphragnl 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.

DRIVEABILITY AND EMISSIONS 2.8L (VIN 5) 6E3-C3-3
ON-CAR SERViCE
FUEL VAPOR CANISnEW
Remove or Disconnect
1. Hoses
from canister. Mark hoses to install on
new canister.
2. Canister.
Install or Connect
1. Canister as removed.
2. Hoses. Make sure connections are correct.
FUEL VAPOR CAMISEER SOLENOID
Remove or Disconnect
1. Negative battery cable.
2. Electrical connector and hoses from solenoid.
3. Solenoid.
Install or Connect
1. Hoses and electrical connector on solenoid.
2. Solenoid, cover, and bolt.
3. Negative battery cable
CANISTER HOSES
Refer to Vehicle Emission Control Information
Label for routing of canister hoses.
PARTS INFORMATION
PART NAME GROUP
.................. Canister, Fuel Vapor 3.130
.......... Solenoid, Fuel Vapor Canister 3.140
....... Valve, Fuel Tank Pressure Control 3.140
THROTTLE BODY VAPOR RESTRICTION PURGE VALVE
VACUUM RELIEF VALVE
FUELTANK PRESSURE
CONTROL VALVE
CONSTANT PURGE ORIFICE PURGE LINE 8P
0350-SY E
Figure C3-4 - Evaporative Emissions Control System Schematic