1988 PONTIAC FIERO Service Repair Manual

CHART C-5
ELECTRONIC SPARK CONTROL (ESC) SYSTEM CHECK
(ENGINE KNOCK, POOR PERFORMANCE, OR POOR ECONOMV)
5.OL (VIN E) "F" SERIES (TBI)
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:
If the ESC system checks OK, but detonation is the
complaint, refer to
Detonation1 Spark knock in Section
"B".

DRIVEABILIW AND EMISSIONS 5.OL (VIN E) 6E2-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.
@ PROBE HARNESS TERMINAL "D" (CKT 486) EVlEW "DIAGNOSTIC
WITH A TEST LIGHT TO 12 V.
IDS" ON FACING PAGE

6EZ-C5-6 5.OL (VlN E) DRIVEABILITY AND EMISSIONS
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DRIVEABILITY AND EMISSIONS 5.OL (VIN E) 6EZ-C6-1
SECTION C6
AIR INJECTION REACTION (A.I.R.) SYSTEM
CONTENTS
GENERAL DESCRIPTION ............... C6-1
PURPOSE ......................... C6-1
OPERATION ...................... C6-1
AIR CONTROL PEDES VALVE .......... C6-1
RESULTS OF INCORRECT OPERATION .... C6-2
DIAGNOSIS
........................ C6-2
OPERATIONAL CHECKS .............. C6-2
AirPump ...................... C6-2
Hoses and Pipes ................. C6-3
GENERAL DESCRIPTION
PURPOSE
The A.I.R. system helps reduce hydrocarbon (HC),
carbon monoxide (CO), and oxides of nitrogen (NO,)
exhaust emissions. It also heats up the catalytic
converter quickly on engine start-up so conversion of
exhaust gases can occur sooner.
A Dual bed converter is used. It consists of a three
way catalyst (which controls all three emissions) in
series with
a two way catalyst (which controls only HC
and
CO) both are in one housing. A pipe between the
two converters allows air to be injected into the second
(two way) converter to increase its efficiency to further
control
HC and CO (Figure C6-1).
As shown in Figure C6-1, air can be directed to:
@ A divert silencer.
@ Exhaust ports; or
@ Catalytic converter.
OPERATION
The system (Figure C6-1) includes:
@ An Air Pump
The air pump is driven by a belt on the front of
the engine and supplies the air to the system.
Intake air passes through a centrifugal filter fan
at the front of the pump; where foreign materials
are separated from the air
by centrifugal force.
@ A Control Valve
Air flows from the pump through an ECM
controlled valve (called a control valve) through
check valves to either the exhaust ports or the
converter.
@ Check Valves
The check valves prevent back flow of exhaust
into the pump in the event of an exhaust backfire
or pump drive belt failure.
@ Necessary Plumbing
Check Valve .................... C6-3
ON-CAR SERVICE
.................... C6-3
DRIVEBELT ...................... C6-3
AIR INJECTION PUMP ............... C6-3
AIR INJECTION CONTROL
(PEDES) VALVE
.................. C6-3
AIR INJECTION CHECK VALVE ......... C6-4
PARTS INFORMATION
................ C6-4
CLOSED LOOP FUEL CONTROL
ECM
1 REDUCING CATALYST - 1 OXlDlZlNG CATALYST
1 5 SENSOR
CHECK VALVE
1 AIR PUMP
1 PORT SOLENOID
CONVERTER SOLENOID
/ ELECTRICAL SIGNALS
FROM ECM
BY-PASS AIR TO ATMOSPHERE
Figure C6-1 - A.I.R. System Operation
AIR CONTROL PEDES VALVE
Pressure Operated Electric Divert / Electric Air
Switching (PEDES) valve is used on this engine. The
diverting and switching functions are electronically
controlled by the
ECM,which grounds to complete the
circuit and energize the solenoid. Self-generated
pressure from the A.I.R. pump is used to operate the
valve, which is completely independent of manifold
vacuum.

6EZ-C6-2 5.OL (VIN E) DRIVEABILITY AND EMISSIONS
Air enters the body of the valve from the pump.
Air pressure builds against the control valve and for:
@ Cold Mode - The port solenoid is energized
which in turn opens the port valve and allows
flow to the exhaust ports.
@ Warm Mode - The port solenoid is de-
energized and the converter solenoid
energized which closes the port valve and
keeps the converter valve seated, thus forcing
flow past the converter valve and to the
converter.
@ Divert Mode - Both solenoids are de-energized
which opens the converter valve, allowing air
to take the path of least resistance,
i.e., out the
divert
/ relief tube to atmosphere.
TO CONVERTER AIR INLET
1 TO EXHAUST PORTS 1 SOLENOID / RELIEF + DIVERT AIR 45 0506-6E
Figure C6-2 - A.I.R. System Control Valve
Air is diverted to the atmosphere under the
following conditions:
@ Rich operation.
@ When the ECM recognizes a problem and sets the
"Service Engine Soon" light.
@ During deceleration.
During high RPM operation when air pressure is
greater than the setting for the internal relief
valve.
RESULTS OF lNCORRECP OPERATION
If no air (oxygen) flow enters the exhaust stream
at the exhaust ports, HC and CO emission levels will
be too high.
Air flowing to the exhaust ports at all times could
increase temperature of the converter.
Air flowing at all times to the catalytic converter
may cause converter overheating during rich
operation. Electrical failure
(open circuit) of the control valve
will divert air flow overboard at all times. Air will
flow to the converter at all times if an open circuit
occurs to the switching valve (converter solenoid).
Mechanical failures in the valves could cause the
air to flow incorrectly to the exhaust ports or the
converter.
DIAGNOSIS
The diagnosis of the AIR system is covered in
CHART C-6 at the end of this section.
OPERATIONAL CHECKS
Air Pump
The air pump is a positive displacement vane type
which is permanently lubricated and requires no
periodic maintenance.
Accelerate engine to approximately
1500 rpm's
and observe air flow from
hose(s). If air flow increases
as engine is accelerated, pump is operating
satisfactorily. If air flow does not increase or is not
present, proceed as follows:
a Inspect
1. For proper drive belt tension.
2. For a leaky pressure relief valve. Air may be
heard leaking with the pump running.
NOTICE: If the engine or underhood compartment is
to be cleaned with steam or high-pressure
detergent, the centrifugal filter fan should
be masked off to prevent liquids from
entering the pump (see Fig.
C6B-3).
NOTICE: The AIR System is not completely
noiseless. Under normal conditions, noise
rises in pitch as engine speed increases.
inspect
3. For a seized Air Injection Pump.
3. Hoses, tubes and all connections for leaks and
proper routing.
5. For air flow from control/switching valve.
6. AIR injection pump for proper mounting and bolt
torque.
7. If no irregularities exist and the AIR injection
pump noise is still excessive, remove and replace
pump.

DRIVEABILITY AND EMISSIONS 5.OL (VIN E) 6EZ-C6-3
CAUTION: Do Not Oil A.I.R. Pump
Hoses and Pipes
inspect
1. Hose or pipe for deterioration or holes.
2. All hoses or pipe connections, and clamp tightness.
3. Hose or pipe routing. Interference may cause
wear.
4. If a leak is suspected on the pressure side of the
system or if a hose or pipe has been disconnected
on the pressure side, the connections should be
checked for leaks with a soapy water solution.
With the pump running, bubbles will form if a
leak exists.
Check Valve
a inspect
1. A check valve should be inspected whenever the
hose is disconnected form a check valve or
whenever check valve failure is suspected.
(A
pump that had become inoperative and had shown
indications of having exhaust gases in the pump
would indicate check valve failure).
2. Blow through the check valve (toward the cylinder
head) then attempt to suck back through the check
valve Flow should only be in one
direction(toward the exhaust manifold). Replace
valve which does not operate properly.
ON-CAR SERVICE
DRIVE BELT
Remove or Disconnect
1. Inspect drive belt for wear, cracks or deterioration
and replace if required. When installing new belt,
it must be seated and fully secured in grooves of
all belt driven components.
AIR INJECTION PUMP
Remove or Disconnect
1. Hold pump pulley from turning by compressing
drive belt, then loosen pump pulley bolts.
2. Drive belt and pulley.
3. Hoses, vacuum, and electrical connections from
Air Injection Control valve.
4. Air pump mounting bolts, and pump assembly
(See Figure
C6-3).
Install or Connect
1. Air pump assembly, and tighten mounting bolts.
2. Spacer and pump pulley against centrifugal filter
fan.
3. Pump pulley bolts and tighten equally to 13 N m
(10 lb, ft).
4. Check
air injection system for proper operation
(see Chart C-6).
Figure C6-3 - Air Pump Service
AIR INJECTION CONTROL (PEDES) VALVE
Remove or Disconnect
1. Battery ground cable.
2. Adapter bolts (See Figure C6-4).
3. Air outlet hoses from valve.
4. Splash guard / cover
5. Electrical connectors and vacuum hoses from
valve.
6. Control valve.
Install or Connect
1. Control valve.
2. Electrical connectors.
3. Splash guard /cover
4. Air hoses to valve.
5. Battery ground cable.
6. Check
system operation (see
CHART C-6).

6E2-C6-4 5.QL (VIN E) DRIVEABILITY AND EMISSIONS
AIR INJECTION CHECK VALVE
Remove or Disconnect
1 . Release clamp and disconnect air hoses from check
valve
.
2 . Unscrew check valve from air injection pipe .
Install or Connect
1 . Screw check valve onto air injection pipe . 23 N . m
(17 Ib . ft.).
2 . Position air hoses on check valve and secure with
clamp
.
PART NAME GROUP
Adapter. AIR Inj Cont Vlv ............. 3.671
Brace. AIR Inj Pump
................. 3.655
Bracket. AIR Inj Pump
............... 3.655
Gasket. AIR
Inj Dvtr Vlv El ............ 3.671
Harness. AIR Inj Cont Vlv
Vac .......... 3.675
Hose. AIR Inj Cont Vlv
................ 3.675
Hose. AIR Inj Cont Vlv Dvtr
........... 3.675
Hose. Ctltc Conv AIR Inj Chk Vlv
....... 3.675
Pipe. AIR
Inj Ctltc Conv Chk Vlv ........ 3.690
Pipe. Ctltc Conv AIR Inj
............... 3.675
Pulley. AIR Inj Pump
................. 3.650
Pump. AIR Inj
..................... 3.660
Silencer AIR Inj Cont Vlv
............. 3.660
Support. AIR Inj Pump
................ 3.660
Valve. AIR Inj Cont
.................. 3.670
Valve. AIR Inj Eng Chk
............... 3.670
Valve. Ctltc Conv AIR Inj Chk
......... 3.670
Figure C6-4 . PEDES Valve Service
Figure
C6-5 . A.I.R. Pump mounting

DRIVEABILITY AND EMISSIONS 5.OL (VIN E) 6E2-C6-5
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