reset PONTIAC FIERO 1988 Service Repair Manual

3-10 STEERING, SUSPENSION, TIRES AND WHEELS DIAGNOSIS
Reminder Keeps Operating With Key In Lock
Cylinder, Driver's Door Open Or Closed; Ceases
When Key Is Removed
Inspect
s Door jamb switch on driver's side misadjusted or
inoperative.
e Wire from signal switch to door jamb switch
shorted.
A. This condition indicates the lock cylinder or
the reminder switch is at fault. To verify,
check for continuity at the
"E" and "F"
male column connector contacts, with the
key removed from the lock cylinder. If
continuity exists, the fault is in the column.
B. Insert the key into the lock, then turn the
lock toward the "Start" position. If the
reminder stops when the key is in the
"Run" position or when it is turned past
"Run" toward "Start," the problem is a
sticky lock cylinder actuator.
COLUMN-MOUNTED DIMMER SWITCH
No "Low" or "High" Beam
Inspect
e Loose connector at dimmer switch
e Improper adjustment
e Internally damaged or worn switch. Check the
continuity on the switch at the It. green and at the
tan switch terminals by pushing in the plunger all
the way.
A click should be heard. If there is no
continuity, replace the dimmer switch. If there is
continuity, refer
to'section 8A for electricaldiag-
nosis.
PIVOT AND SWITCH ASSEMBLY
Switch Inoperative: No "Low," "High" and/or
"Wash"
e Loose body-to-switch connector
a Broken or damaged switch
Internally damaged or worn switch. Connect a
new switch without removing the old one. If the
system functions, replace the switch. If the
system doesn't function, refer to Section
8A for
electrical diagnosis.
STEERING GEAR AND PUMP LEAKS
General Procedure
Inspect
s Overfilled reservoir
s Fluid aeration and overflow
e , Hose connections
Verify exact point of leakage Example:
Torsion bar, stub shaft and
adjuster seals are close together; the exact
spot where the system is leaking may not be
clear.
Example: The point from which the fluid is
dripping is not necessarily the point where
the system is leaking; fluid overflowing from
the reservoir, for instance.
e When service is required:
A. Clean leakage area upon disassembly.
B. Replace leaking seal.
C. Check component sealing surfaces for
damage.
D. Reset bolt torque to specifications, where
required.
Some complaints about the power steering system
may be reported as:
A. Fluid leakage on garage floor
B. Fluid leaks visible on steering gear or pump
C. Growling noise, especially when parking or
when engine is cold
D. Loss of power steering when parking
E. Heavy steering effort
When troubleshooting these kinds of complaints,
check for an external leak in the power steering system.
For further diagnosis of leaks, refer to External
Leakage Check in this section.
External Leakage Check
Fig. 12
The purpose of this procedure is to pinpoint the
location of the leak.
In some cases, the leak can easily be located. But,
seepage-type leaks may be more difficult to isolate. To
locate seepage leaks, use the following method.
1. With the engine off, wipe dry the complete power
steering system.
2. Check the fluid level in the pump's reservoir. Add
fluid if necessary.
3. Start the engine, then turn the steering wheel
from stop to stop several times. Do not hold it at
a stop for any length of time, as this can damage
the power steering pump. It is easier if someone
else operates the steering wheel while you search
for the seepage.
4. Find the exact area of the leak and repair leak.
SEAL REPLACEMENT
RECOMMENDATIONS
Lip seals, which seal rotating shafts, require
special treatment. This type of seal is used on the
steering gear and on the drive shaft of the pump. When
there is a leak in one of these areas, always replace the
seal(s), after inspecting and thoroughly cleaning the
sealing surfaces. Replace the shaft only if very severe
pitting is found. If the corrosion in the lip seal contact
zone is slight, clean the surface of the shaft with crocus
cloth. Replace the shaft only if the leakage cannot be
stopped by first smoothing with crocus cloth.

STEERING, SUSPENSION, TIRES AND WHEELS DIAGNOSIS 3.13
in doubt about the condition, compare with a
shock known to be good.
Noisy
For struts, follow Steps 1 through 3.
1. Check all mountings for proper torque. A loose
mounting will cause a noise.
2. If all mountings are intact, bounce the car as in
Step
4 (weak) to isolate the suspected unit.
3. If practical, ride with the owner to be sure you
understand the complaint, before proceeding to
next step.
4. If one of the rear shocks is noisy, the rear axle
should be supported at least enough to unload the
shock mounts. Disconnect the lower mounting of
the suspected shock. Quickly push the shock all
the way in, then all the way out.
A hissing noise
is normal.
5. Other objectionable noises may be detected by
stroking. Any sound other
than hissing is
abnormal; replace the shock.
Leaks
1. Fully extend the strut/shocks (wheels
unsupported) to expose the seal cover area for
inspection.
2. Look for
signs of leaks in the seal cover area.
3. A slight trace of fluid is NOT cause for
replacement; the seal permits some seepage to
lubricate the piston rod. There is a built in fluid
reserve to allow for seepage.
4. A leaking strut dampener/shock can easily be
found because there will be fluid around the seal
cover and an excessive amount of fluid on the
strut
dampener/shock. A leaking strut
dampener/shock must be replaced.
BENCH CHECKS
Strut Dampeners and Regular Shock Absorbers
(Standard and Firm Ride)
Regular strut dampenerdrear shocks use a
gas-filled cell in the fluid reservoir. Aeration or
foaming of the fluid is eliminated, as the gas and the
fluid cannot mix.
Proceed with the actual bench check as follows:
1. Clamp the strut dampener/shock UPSIDE
DOWN in the vise. Do not clamp on the reservoir
tube or the mounting threads. If a lag is noticed
when it is stroked, it means the gas-filled cell has
ruptured and replacement is necessary.
2. Pump strut dampener/shock by hand at various
rates of speed and note the resistance.
3. Rebound resistance normally is stronger than
compression resistance by about 2 to 1. However,
the resistance should be smooth and constant for
each stroking rate.
4. Compare with a strut dampener/ shock known to
be good.
5. It is normal to hear a hissing noise. The following
symptoms are abnormal and are reason for
replacement. A.
A skip or lag at reversal near mid-stroke.
B. A seize (except at either extreme end of
travel).
C. A noise (such as a grunt or squeal) after
completing one full stroke in both
directions.
D. A clicking noise at fast reversal.
E. Fluid leakage.
TIRE DIAGNOSIS
Irregular and Premature Wear
Figs. 14 and 15
Irregular and premature tire wear has many
causes. Some of them are: incorrect inflation pressures,
lack of regular rotation, driving habits, or improper
wheel alignment. If wheel alignment is reset due to a
tire wear condition, always reset toe as close to zero
degrees as the specification allows.
1. WEAR INDICATORS I
Fig. 14 Tire Wear Indicator
If the following conditions are noted, rotate the
tires:
@ Front tire wear is different from rear.
Uneven wear exists across the tread of any tire.
e Left and right front tire wear is unequal.
Left and right rear tire wear is unequal.
Check wheel alignment if the following
conditions are noted:
e Left and right front tire wear is unequal.
Wear is uneven across the tread of any front tire.
e Front tire treads have a scuffed appearance with
"feather" edges on one side of the tread ribs or
blocks.
Wear Indicators
Fig. 16
The original equipment tires have built-in tread
wear indicators to show when the tires should be
replaced. These indicators will appear as 12.7 mm
(1/2") wide bands when the tire tread depth becomes
1.6 mm (2/32"). When the indicators appear in 2 or
more grooves at
3 locations, replace the tire.

3C-6 FRONT SUSPENSION
Ball Jo~nt-Replacement
1 Raise car, support w~th floor stands under frame
2 Remove tlre and wheel assembly.
3. Place floor jack under control arm sprtng seat
CAUTION Floor jack must
remaln under control arm sprbng seat dur~ng removal and tnstallat~on to retam sprlng and control arm In posttlon.
4 Remove cotter ptn, and loosen castellated nut Use J 24292A to break ball jolnt loose from knuckle Re
move tool, and separate jolnt from knuckle
5 Gu~de lower control arm out of openlng In splash sh~eld w~th a putty kntfc or stmtlar tool
6 Remove grease fttt~ngs, and ~nstall tools as shown below.
Press ball jolnt out of lower control arm
Inspection-Steering Knuckle
Installation
See NOTICE on Page 3C.1 of this section.
1. Position ball joint into lower control arm and press in
until it bottoms on the control arm, using tools as
illustrated below.
Grease purge on seal must be located facing inboard.
2. Place ball joint stud in steering knuckte.
3. Torque ball stud nut to 120
Nm (90 Ib. ft.). Then
tighten an additional amount enough to align slot in
nut with hole in stud. Install cotter pin.
4, Install and lubrtcate ball joint fitting until grease appears
at the seal.
5. Install tire and wheel assembly.
6. Check front alignment as described in Section 3A. Reset as requrred. Lower car.
Inspect the tapered hole
In the stcerlng knuckle Remove
any dtrt. If out.of-roundness, defor:nat~on or damage IS noted, the knuckle MUST be replaced
Inspection-Ball Joint
Ball
jo~nt seals should be carefully inspected for cuts
and tears. Whenever cuts or tears are found, the ball joint
MUST be replaced.
REMOVING BALL JOINT
INSTALLING BALL JOINT
LOWER CONTRCL ARM
FI~ 606 Remov~ng and Installing Ball Joint

REAR AXLE 481-1 5
Fig. 17 Installing Service Shims
left shim and add difference to the
right side. Keep total shim thickness
at a value equal to that obtained in
step b.
NOTICE: Original light drag is caused by weight
of the case against the carrier while additional drag
is caused by side bearing preload.
For convenience in setting backlash and tooth
contact, the preload will not be added until the
final step.
4. Check backlash and tooth pattern as described in
the following section. The bearing caps must be
installed and the bolts torqued to specified torque
(follow assembly sequence below).
5. When backlash and tooth pattern operations are
complete, remove shim packs taking care not to
mix them. Select new shims for each side
.004"
thicker than those removed and install each shim
on its proper side. This additional thickness will
provide proper bearing preload. It will be
necessary to tap the
final shim into place with a
soft hammer and tool
5-25588 (Fig. 17).
1. FRONT PINION
BEARING AND
RACE
2. SPACER
J 351 18-5
3.
SIDE DISCS J 21 777-45
4. THRU BOLT J 21 777-43 5.
SPACER
J 21777-42
6. REAR PINION
BEARING
7. ARBOR
J 23597-1
8. GAGE PLATE
351 18-2
J10003-4B1 -F
Fig. 18 Hypoid Pinion and Bearing Shim Selection
1. Drive front pinion bearing cup in the carrier
(Item a) with tool
5-7817. (Fig. 19).
1-J-8092 DRIVE
NOTICE: Check total rotational torque. Total
torque with differential case preloaded and pinion Fig. 19 Front Pinion Bearing Cup Installation
installed should be 4 to 6 in. lb, over pinion bearing
preload specification. If total rotational torque 2. Fit spacer (item
b) into carrier bore.
does
not- meet this specification, reset the
differential bearing preload spacers as developed in 3. Slide the rear pinion bearing and cap (item f) onto
steps
3 thru 5. the
thru bolt (item d) and rear bearing into axle
housing.
Assemble 4. Install thru bolt (item d) and rear bearing and cap
(item
f) into axle housing.
5. Assemble front bearing cone (item a) and spacer
(item e) onto thru bolt.
Pinion 6. Rotate nut and shaft and increase torque on the Hypoid Pinion and Bearing Shim Selection
nut until a rotational toraue of 1.7 to 2.8 N-m
(15-22 lb. in.) is obtained: Rotate the thru bolt
NOTICE: Select pinion head positioning shim using back
and forth during tightening to ensure
pattern setting kit
J 35118-A. Refer to Fig. 18. correct
seating of bearing.

REAR AXLE 48-1 7
approached. No further tightening should be
attempted until the pre-load has been checked.
7. Check pre-load by using an inch pound torque
wrench.
NOTICE: After pre-load has been checked, final
tightening should be done very carefully. For
example, if when checking, pre-load was found to
be 0.6
N-m (5 lbs. in.), any additional tightening
of the pinion nut can add many additional pound
inch of torque. Therefore, the pinion nut should be
further tightened only a little at a time and the
pre-load should be checked after each slight
amount of tightening. Exceeding pre-load
specifications will compress the collapsible spacer
too far and require the installation of a new
collapsible spacer.
While observing the preceeding note, carefully set
pre-load at 2.7 to 3.6
N-m (24 to 32 1b.in.) on new
bearings or 1.0 to 1.4
N m (8 to 12 1b.in.) on used
bearings.
8. Rotate pinion several times to assure that
bearings have been seated. Check pre-load again.
If pre-load has been reduced by rotating pinion,
reset pre-load to specifications.
Rear Axle Backlash Adjustment
1. Install rear axle case into carrier, using shims as
determined by the side bearing pre-load
adjustment.
2. Rotate rear axle case several times to seat
bearings, then mount dial indicator. Use a small
button on the indicator stem so that contact can
be made near heel end of tooth. Set dial indicator
so that stem is in line as nearly as possible with
gear rotation perpendicular to tooth angle for
accurate backlash reading.
3. Check backlash at three or four points around
ring gear. Lash must not vary over
.05mm (.002")
around ring gear. Pinion must be held stationary
when checking backlash. If variation is over
.05mm (.002") check for burrs, uneven bolting
conditions or distorted case flange and make
corrections as necessary.
4. Backlash at the point of minimum lash should be
between .13 and
.23mm (.005" and ,009") for all
new gears.
5. If backlash is not within specifications, correct by
increasing thickness of one shim and decreasing
thickness of other shim the same amount. This
will maintain correct rear axle side bearing
pre-load.
For each
.03mm (.001") change in backlash
desired, transfer
.05mm (.002") in shim
thickness. To decrease backlash
.03mm (.00lU),
decrease thickness of right shim .05mm (.002")
and increase thickness of left shim .05mm (.
002 "). To increase backlash .05mm (.002 ")
increase thickness of right shim .10mm (.004")
and decrease thickness of left shim .10mm (.
004"). 6.
When backlash is correctly adjusted, remove both
bearing caps and both shim packs.
Keep packs in their respective position, right or
left side.
Select a shim
.10mm (.004") thicker than the one
removed from the left side, then insert left side
shim pack between the spacer and the left bearing
race. Loosely install bearing cap.
7. Select a shim
.10mm (.004") thicker than the one
removed from right side and insert between the
spacer and the right bearing race. It will be
necessary to drive the right shim into position
(Fig. 614).
8. Torque to 75 Nem (55 1b.ft.).
9. Recheck backlash
and correct if necessary.
10. Install axles (See Rear Axle Installation).
11.
Use sealant 1052366 or cover gasket
only.
Install cover and torque cover bolts to 27
N-m (20 1b.ft.).
12. Fill rear axle to proper level with the specified
lubricant. Refer to specifications.
LIMITED SLIP REAR AXLE (GONE TYPE)
The cone-type limited-slip differential has several
definite operating characteristics. An understanding of
these characteristics is necessary as an aid to diagnosis.
The clutch energizing force comes from the
thrust side of the gears. Consequently, a free spinning
wheel may not have enough resistance to drive torque
to apply the clutch cones. If this occurs, apply the
parking brake a few notches which will provide enough
resistance to energize the clutch cones.
Energizing the clutch cones is independent of
acceleration; therefore, a very slow application of the
throttle on starting is recommended to provide
maximum traction by preventing "break away" of
either rear wheel.
Improper operation is generally indicated by cone
slippage or grabbing. Sometimes this produces a
chatter or whirring sound. However, these sounds do
not always indicate failure as they could be produced
from a lack of proper lubrication. For example, under
certain conditions where one wheel is on
a very slippery
surface and the other on dry pavement, wheel spin can
occur if over acceleration is attempted. Continued
spinning may cause audible noise, such as a whirring
sound, due to the cones lacking sufficient lubricant.
This does not necessarily indicate failure of the unit.
During regular operation (straight ahead driving)
when both wheels rotate at equal speeds, there is an
approximately equal driving force delivered to each
wheel. When cornering, the inside wheel delivers extra
driving force causing slippage in both clutch cones.
Consequently, the operational life of the limited slip
unit is dependent upon equal rotation of both wheels
during straight ahead operation. If wheel rotation for
both rear wheels is not equal during straight ahead
operation, the limited-slip unit will constantly be
functioning as if the vehicle were cornering. This will
impose constant slippage on the clutch cones and will
eventually lead to abnormal wear on the clutch cones.
Therefore, it is important that there be no excessive
differences in the rear wheel tire sizes, air pressures, or

6EZ-C2-4 DRIVEABILITY AND EMISSIONS - 5.OL (VIN El
[isj FUEL METER COVER bL BODY ASSEMBLIES
1 THROTTLE BODY ASSEMBLY
1 IDLE AIR CONTROL VALVE ASSEMBLY - FILTERED AIR INLET
PlNTLE
TWRO$TLE VAWE
VACUUM PORTS - FOR ENGINE OR EMISSION
CONTROLS
8P 0319-SY 111 5W7
Figure C2-5 - ldle Air Contol System
ldle Air Control (IAC) Valve
The purpose of the idle air control (IAC) valve , is
to control engine idle speed, and prevent stalls due to
changes in engine load (see Figure
C2-5) .
The IAC valve, mounted on the throttle body,
controls bypass air around the throttle valve By
moving a conical valve IN (to decrease air flow) or
OUT (to increase air flow), a controlled amount of air
can move around the throttle valve. If rpm is too low,
more air is bypassed around the throttle valve to
increase rpm.
11 rpnl is too high, less air is bypassed
around the
throt:le valve to decrease rpm.
The IAC valve moves in small steps called
"Counts," and can be monitored by
a "Scan" tool which
plugs into the assembly line data
link (ALDI,)
connector
During idle, the proper position of the IAC valve is
calculated by the ECM based on battery voltage,
coolant temperature,
ellgine load, and engine rpm. If
the rpm drops below a specified rpm, and the throttle
valve is closed, the ECM senses a near stall condition.
The ECM will then calculate a new IAC valve position
to prevent stalls.
If the IAC valve is disconnected or connected with
the engine running, the idle
rpnl may he wrong. In
this case, the
IAC valve may he reset by turning the
ignition switch "ON" and
"OFF" one time
'I'he IAC valve affects only the idle characteristics
of the engine
If it i.; ol)cltl fullv, too much ,LII. tc 111 I)(>
BALL BEARING ASSEMBLY -
STATOR ASSEMBLY
ROTOR
ASSEMBL
I
SPRING
PlNTLE
LEAD SCREW A
Figure C2-6 - ldle Air Control (IAC) Valve
allowed to the manifold and idle speed will he high. if
it is stuck closed, too little air will be
allo\verl in the
manifold, and idle speed will be too low. If it is stuck
part way open, the idle may be rough, and will not
respond to engine load changes.
On
4.3L (VIN Z) V6, LB4 engines, for "B" and "G"
cars, the valve is thread mounted, with a dual taper,lO
mm diameter pintle (Figure C2-6). If replacement is
necessary, use only an IAC valve with the correct part
number and appropriate pintle shape and diameter.
I THROTTLE VALVE
ENGINE CONTROL MODULE (ECM)
,q
THROTTLE POSITION
SENSOR (TPS)
Figure C2-7 - Throttle Position Sensor
Throttle Position Sensor (TPS)
The throttle position sensor ('I'PS), is mounted on
the side of the throttle body opposite the throttle lever
assembly. Its function is to sense the current throttle
valve position
and relkly that information to the ECM
(Figure (22-7). Knowledge of throttle position allows
lhe ECM to generate the recluired i~jector control
signals (base pulse). If the 'I'PS senses a wide open
throttle,
a voltc\ge sic,ll,~I il~tlic~ttinq this condition 13

DRIVEABILITY AND EMISSIONS - 5.BL (VIN E) 6E2-CZ-7
Refer to the disassembled view (Figure C2-8) for
identification of parts during repair procedures.
Service repair of individual components is performed
without removing the TBI unit from the engine. If
removed, it is essential that care is taken to prevent
damage to the throttle valve or sealing surface while
performing any service.
Whenever service is performed on the TBI or any
of its components, first remove the air cleaner, adapter
and air cleaner gaskets. Discard the gaskets and
replace them with new ones before replacing the air
cleaner after service is complete.
When disconnecting the fuel lines, be sure to use a
backup wrench
(J-29698-A, or BT8251-A, or
equivalent) to keep the TBI nuts from turning.
Fuel Pressure Relief
The TBI Model 220 on this engine contains a
constant bleed feature in the pressure regulator that
relieves pressure. Therefore, no special pressure relief
procedure is required.
Fuel System Pressure Pest
A fuel system pressure test is part of several of the
diagnostic charts and symptom checks. To perform
this test, follow this procedure:
1. Turn engine "OFF" to relieve fuel pressure.
2. Remove air cleaner and plug THERMAC vacuum
port on TBI.
3. Uncouple fuel supply flexible hose in engine
compartment. Install fuel pressure gage
J-29658AlBT8205 and adapter 29658A-85
between steel line and flexible hose.
4. Tighten gage in line to ensure no leaks occur
during testing.
5. Start car and observe fuel pressure reading. It
should be 62-90
kPa (9-13 psi); if not, refer to
CHART A-7.
6. Relieve fuel pressure.
7. Remove fuel pressure gage.
8. Reinstall fuel line.
9. Start car and check for fuel leaks.
10. Remove plug from vacuum port and install air
cleaner with new gasket.
Cleaning and inspection
All TBI component parts, with the exception of
those noted below, should be cleaned in a cold
immersion cleaner such as Carbon
X (X-55) or
equivalent.
NOTICE: The throttle position sensor ('I'PS), idle air
control
(IAC) valve, pressure regulator
diaphragm assembly, fuel injectors or other
components containing
rubber,should NOT be placed in a solvent
or cleaner bath. A chemical reaction will
cause these parts to swell, harden or
distort. Do not soak the throttle body with
the above parts attached. If the throttle
body assembly requires cleaning, soaking
time in the cleaner should be kept to a
minimum. Some models have hidden
throttle shaft dust seals that could lose
their effectiveness by extended soaking.
1. Clean all metal parts thoroughly and blow dry
with shop air. Be sure that all fuel and air
passages are free of dirt or burrs.
2. Inspect mating casting surfaces for damage that
could affect gasket sealing.
Thread Locking Compound
Service repair kits are supplied with a small vial
of thread locking compound with directions for use. If
material is not available, use Loctite 262, or
GM part
number 10522624, or equivalent.
NOTICE: Do not use a higher strength locking
compound than recommended, since to do
so could make removing the screw
extremely difficult, or result in damaging
the screw head.
FUEL METER COVER ASSEMBLY
Replacement (Figure
C2-9)
The fuel meter cover assembly contains the fuel
pressure regulator assembly. The regulator has been
adjusted at the factory and should only be serviced as
a complete preset assembly.
CAUTION: DO NOT remove the four screws
securing the pressure regulator to
the fuel meter cover. The fuel
pressure regulator includes a large
spring under heavy compression
which, if accidentally released,
could cause personal injury.
Disassembly might also result in a
fuel leak between the diaphragm
and the regulator container.
Remove or Disconnect
I. Electrical connectors to fuel injectors. (Squeeze
plastic tabs and pull straight up.)
2. Long
and short fuel meter cover screw assemblies.
3. Fuel meter cover assembly.

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

6E3-CZ-4 Z.8L (WIN 5) DRIVEABILITY AND EMISSIONS
FUEL INJECTOR
1 INTAKE MANIFOLD
1 INTAKE VALVE
1 ELECTRICAL TERMINAL
151 "0" RING
1 FUEL RAIL 4.5 101ME
Figure C2-4 Fuel Injector
The pressure regulator is mounted on the fuel rail,
and is replaced as an assembly.
If the pressure is too low, poor performance could
result. If the pressure is too high, excessive odor and a
Code
45 may result. CHART A-7 has information on
diagnosing fuel pressure conditions.
IDLE AIR CONTROL (IAC) VALVE
The purpose of the idle air control (IAC) valve
(shown in Figure C2-5), is to control engine idle speed,
while preventing stalls due to changes in engine load.
The IAC valve, mounted in the throttle body,
controls bypass air around the throttle valve. By
moving a conical valve IN
(to decrease air flow) or
OUT (to increase air flow), a controlled amount of air
can move around the throttle plate. If rprn is too low,
more air is bypassed around the throttle valve to
increase rpm. If rprn is too high, less air is bypassed
around the throttle valve to decrease rpm.
The IAC valve moves in small steps called
"counts," which can be measured by some test
equipment which plugs into the ALDL.
During idle, the proper position of the IAC valve is
calculated by the ECM based on battery voltage,
coolant temperature, engine load, and engine rpm.
If
the rprn drops below a specified rpm, and the throttle
plate is closed, the ECM senses a near stall condition.
SINGLE TAPER VALVE
DUAL TAPER VALVE
BLUNT
PINTLE
Figure C2-5 IAC Valve Designs
The ECM will then calculate a new valve position to
prevent stalls.
If the IAC valve is disconnected and reconnected
with the engine running, the idle rprn may be wrong.
In this case, the IAC can be reset by starting the
engine momentarily and then turning the ignition
"OFF".
Different designs are used for the IAC valve. Re
sure to use the correct design when replacement is
required.
The IAC valve affects only the idle characteristics
of the vehicle. If it is open fully, too much air will be
allowed into the manifold and idle speed will be high.
If it is stuck closed, too little air will be allowed in the
manifold, and idle speed will be too low. If it is stuck
part way open, the idle may be rough, and will not
respond to engine load changes.
FUEL PUMP ELECTRICAL CIRCUIT
When the ignition is first turned "ON" without
the engine running, the ECM will turn 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 will shut the fuel pump
"OFF"
and wait until the engine starts. As soon as the
engine is cranked, the ECM will turn the relay
"ON"
and run the fuel pump.

DRIVEABILITY AND EMISSIONS 2.8L (VIN S) 6E3-CZ-15
NOTICE: Before instal ling new idle air control valve
assembly, the position of its pintle
MUST
be checked. If pintle is extended too far,
damage to the assembly may occur.
Measure
@ Distance from gasket mounting surface of IAC
valve assembly
(70) to tip of pintle, Dimension
"A" in Figure
C2-19.
Adjust
If distance is greater that 28 mm (1 118 in.), reduce -
it as follows:
a. If
IAC valve assembly has
a "collar" around
electrical connector end, use firm hand pressure
on pintle to retract it. (A slight side-to-side motion
may help.)
b. If IAC valve assembly has "no collar", compress
pintle-retaining spring toward body of the IAC
and try to turn pintle clockwise.
@ If pintle will turn, continue turning until
28mm
(1 118 in.) is reached. Return spring to
original position, with straight part of spring
end lined up with flat surface under the pintle
head.
@ If pintle will not turn, use firm hand pressure
to retract it.
Install or Connect
1. New IAC valve assembly gasket (71) on IAC valve
assembly
(70).
2. IAC valve assembly in idle airlvacuum signal
housing assembly
(60).
Tighten
IAC valve assembly to 18N.m (13 ft. Ibs.), with
wrench on hex surface only.
3. Electrical connector at IAC valve assembly (70).
Important
No physical adjustment is made to the IAC
assembly after installation.
IAC resetting occurs
after reinstallation on the vehicle, and is reset
after the engine is started and then the ignition
turned off.
IDLE AIR / VACUUM SIGNAL HOUSING
ASSEMBLY
(With
IAC Removed) (Figure C2-20)
Remove or Disconnect
1. Idle airlvacuurn signal assembly attaching screw
assemblies
(65) and (66).
2. Idle airlvacuum signal housing assembly (60).
3. Idle airlvacuum signal assembly gasket (67).
10 THROTTLE BODY ASSEMBLY
60 IDLE AIWVACUUM SIGNAL
HOUSING ASSY
65 SCREW ASSY - IDLE AIWVACUUM SIGNAL
HOUSING ASSY.
66 SCREW
ASSY
- IDLE AIWVACUUM SIGNAL
HOUSING ASSY
67 GASKET - IDLE AIR VACUUM SIGNAL ASSY 70 VALVE ASSY - IDLE AIR CONTROL (IAC) 71 GASKET - IAC VALVE ASSY
Figure C2-20 Idle AirIVacuum Signal Housing
Assembly
Tighten
@ Attaching screw assemblies (starting in center
and
moving outward) to 3.0 N.m (27.0 in. Ibs.).
COOLANT CAVITY COVER AND O-RING
(Figure
C2-21)
Remove or Disconnect
1. Coolant cover attaching. screw assemblies (45).
2. Coolant cavity cover (40).
3. Coolant cover to throttle body O-ring (46).
Inspect
@ Gasket and O-ring surfaces, for damage and
corrosion which might effect sealing.
Install and Connect
1. Lubricate coolant cover to throttle body O-ring (46)
with ethylene glycol antifreeze.
2. O-ring in throttle body assembly (10).
:3. Coolant cavity cover.
4. Coolant cover attaching screw assemblies (451,
applying pressure against throttle body (1 0).