1995 ISUZU TROOPER Workshop Manual

DRIVEABILITY AND EMISSIONS 6E2-129
CHART C-2A
INJECTOR BALANCE TEST
NOTE: The entire test should NOT be repeated more than once without running the engine to prevent flooding.
(This includes any retest on faulty injectors).
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. Ignition "OFF".
2. Connect fuel pressure gauge and injector tester.
3. Ignition "ON".
4. Bleed off air gauge. Repeat until all air is bled from gauge.
Step 2. Run test:
Step 3.
1. Ignition "OFF" for 1 0 seconds.
2. Ignition "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 (1.5 psi) difference, either more or less, in pressure from the
average).
If no problem is found, review "symptoms" Section "8".
Injector connector
Tester J34730-3
Fig. 6E2-83
Gauge J34730-1
BATTERY
EXAMPLE
CYLINDER 1 2
3 4
5 6 7 8
1ST
READING 293 kPa 293 kPa 293 kPa 293 kPa 293 kPa 293 kPa 293 kPa 293 kPa
(43 psi) (43 psi) (43 psi) (43 psi) (43 psi) (43 psi) (43 psi) (43 psi)
2ND
READING 131 kPa 131 kPa 131 kPa 115 kPa 131 kPa 145 kPa 131 kPa 131 kPa
(19 psi) (19 psi) (19 psi) (17 psi) (19 psi) (21 psi) (19 psi) (19
psi)
AMOUNT
OF DROP 162 kPa 162 kPa 162 kPa 178 kPa 162 kPa 148 kPa 162 kPa 162 kPa
(24 psi) (24 psi)
(24 psi) (26
psi) (24 psi) (21 psi) (24 psi) (24 psi)
OK OK OK FAULTY, RICH OK FAULTY, LEAN OK OK
(TOO MUCH (TOO LITTLE
FUEL DROP) FUEL DROP)

6E2-130 DRIVEABILITY AND EMISSIONS
CHART C-2C
IDLE AIR CONTROL (lAC) SYSTEM CHECK
Circuit Description:
The engine control module (ECM) controls engine idle speed with idler air control (lAC) valve. To increase idle
speed, the ECM retracts the lAC valve pintle away from its seat, allowing more air to bypass the throttle bore. To
decrease
idle speed, it extends the lAC valve pintle towards its seat, reducing bypass air flow. A "Scan tool" will
read the ECM commands to the lAC valve in counts. Higher counts indicate more air bypass (higher idle). Lower
counts indicate
less air is allowed to bypass (lower idle).
Test Description:
Number below re{er to circled numbers on the diagnostic chart.
1. The lAC tester is used to extend and retract the lAC valve. Valve movement is verified by an engine speed
change.
If no change in engine speed occurs, the valve can be retested when removed from the throttle body.
2. This step checks the quality of the lAC movement in step 1. Between 700 revolution per minute (rpm) and
about
1500 rpm, the engine speed should change smoothly with each flash of the tester light in both extend
and retract.
If the lAC valve is retracted beyond the control range (about 1500 rpm), it may take many flashes
in the extend position before engine speed will begin to drop. This is normal on certain engines, fully
extending lAC may cause engine stall. This may be normal.
3. Steps 1 and 2 verified proper lAC valve operation. This step checks the lAC circuits. Each lamp on the node
light should flash red and green while the lAC valve is cycled. While the sequence of color is not important if
either light "OFF" or does not flash red and green, check the circuits for faults, beginning with poor terminal
contacts.
Diagnostic Aids:
A slow, unstable, or fast idle may be caused by a non-lAC system problem that cannot overcome by the lAC valve.
Out
of control range lAC "Scan tool" counts will be above 60 if idle is too low, and zero counts if idle is too high. The ..-...
following checks should be made to repair a non-lAC system problem. _......._
• Vacuum Leak (High Idle)
If idle
is too high, stop the engine. Fully extend (low) lAC with tester.
Start engine.
If idle speed is above 800 rpm, locate and correct vacuum leak including PCV system. Also check
for binding of throttle blade or linkage.
•
Lean heated oxygen sensor signal (High Air/Fuel Ratio)
The
idle speed may be too high or too low. Engine speed may vary up and down and disconnecting the lAC
valve
does not help. Diagnostic trouble code 44 may be set. "Scan tool" oxygen (02) voltage will be less than
100 mV (.1 volt). Check for low regulated fuel pressure, water in fuel, or a restricted injector.
• Rich heated oxygen sensor signal (Low Air/Fuel Ratio)
The
idle speed will be too low. "Scan tool" lAC counts will usually be above 80. System is obviously rich and
may exhibit
black smoke in exhaust.
"Scan tool" 02 voltage will be fixed about 750 mV (.75 volt).
Check
for high fuel pressure, leaking or sticking injector. Silicon contaminated heated oxygen sensor will
"Scan
tool" an 02 voltage slow to respond.
• Throttle Body
Remove
lAC valve and inspect bore for foreign material.
• lAC Valve
Electrical Connections
lAC valve
connections should be carefully checked for proper contact.
• PCV Valve
An incorrect or faulty PCV valve may result in an incorrect idle speed.
• Refer to "Rough, Unstable, Incorrect Idle or Stalling" in "Symptoms," Section "6E2-B".
• If
intermittent poor driveability or idle symptoms are resolved by disconnecting the lAC, carefully recheck
connections,
valve terminal resistance, or replace lAC.

DRIVEABILITY AND EMISSIONS 6E2-131
CHART C-2C
IDLE AIR CONTROL (lAC) SYSTEM CHECK
CD • IGNITION "OFF", CONNECT IDLE AIR CONTROL (lAC) DRIVER* TO lAC VALVE. • SET PARKING BRAKE, BLOCK WHEELS, AIR CONDITIONING "OFF".
• IDLE ENGINE IN PARK (A/T) OR NEUTRAL (MIT). • INSTALL "SCAN TOOL" AND DISPLAY REVOLUTION PER MINUTE (RPM). • WITH lAC DRIVER, EXTEND AND RETRACT lAC VALVE. • ENGINE SPEED SHOULD DECREASE AND INCREASE AS lAC IS CYCLED.
I
1 I • RPM CHANGES I NO RPM CHANGE I
I I • RPM SHOULD CHANGE SMOOTHLY
WITH EACH • CHECK lAC PASSAGES.
I FLASH OF THE lAC DRIVER LIGHT FROM 700 RPM • IF OK, REPLACE lAC.
TO ABOUT 1500 RPM. DOES IT?
I
~ cf
• INSTALL APPROPRIATE lAC NODE LIGHT* IN • CHECK lAC PASSAGES.
l ENGINE CONTROL MODULE HARNESS. • IF OK, REPLACE lAC. ®
• CYCLE lAC
DRIVER AND NODE LIGHTS.
• BOTH LIGHTS SHOULD CYCLE RED AND GREEN BUT NEVER "OFF" AS RPM IS CHANGED OVER
ITS RANGE. DO THEY?
I
cf ~ IF CIRCUIT(S) DID NOT TEST GREEN AND RED, CHECK •
USING THE OTHER CONNECTOR ON THE lAC
FOR: DRIVER
PIGTAIL, CHECK RESISTANCE
•
FAULTY CONNECTOR TERMINAL CONTACTS. ACROSS
lAC COILS.
• OPEN CIRCUITS INCLUDING CONNECTIONS. •
SHOULD BE 40 TO 80 OHMS BETWEEN lAC
• CIRCUITS SHORTED TO GROUND OR VOLTAGE. TERMINALS "A" TO "B" AND "C" TO "D".
• FAULTY ENGINE CONTROL MODULE CONNECTION I OR ENGINE CONTROL MODULE.
~
l REPAIR AS NECESSARY AND RETEST. l NOT OK I .
_l
• CHECK RESISTANCE BETWEEN lAC I REPLACE lAC VALVE I TERMINALS "B" AND "C" AND "A" AND RETEST. AND "D". • SHOULD BE INFINITE.
I
~
l
I NOT OK I
]
AC DRIVER AND NODE LIGHT REQUIRED. * I J lAC VALVE AND CIRCUIT OK. I REPLACE lAC VALVE J 37027 FROM KENT-MOORE, INC. REFER TO "DIAGNOSTIC AIDS" ON AND RETEST. FACING~
~ CLEAR DIAGNOSTIC TROUBLE CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NORMAL "CHECK ENGINE" MALFUNCTION
INDICATOR LAMP OPERATION.
------

6E2-132 DRIVEABILITV AND EMISSIONS
CHART C-20
INDUCTION AIR CONTROL PLATE SYSTEM CHECK
(DOHC ONLY)
Circuit Description:
The Induction Air Control Plate system is used to control air to the Induction intake valves when engine speed is
between
2950-4150. For this system, the length of the intake pipe is changed to provide a high torque throughout
the entire field by means
of the "ON" and "OFF" operations of the vacuum switching solenoid mounted to the
common chamber duct.
This system consists
of the Induction air control plate mounted in the Common chamber duct and a vacuum
operated diaphragm which moves the
Induction air control plate linkage. The vacuum to the diaphragm is turned
"ON" or "OFF" by a vacuum switching solenoid which is electrically operated by the Engine Control Module.
Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Without the proper vacuum being available at the solenoid the system will not function properly.
2. When the ignition is "ON" and the engine not running the solenoid should not be energized.
Since the solenoid is normally open the vacuum should
be able to pass to the actuator.
3. With the diagnostic test terminal grounded the engine control module should ground WHT /BLU which should
energize the solenoid and
not allow vacuum to pass to the actuator.
4. This step, as well as the following steps, check for circuit continuity.
INDUCTION AIR VALVE
fi~
__ __...._ MANIFOLDVACUUM
r-=~=-~ N.O.
VACUUM ACTUATOR
TO IGNITION IIi SWITCH ENGINE
FUSE
fl""'v---BLK/YEL
15A
INDUCTION AIR CONTROL
SOLENOID
'----WHT/BLU---1
Fig. 6E2-85 ECM
INDUCTION AIR CONTROL DRIVER
•

DRIVEABILITV AND EMISSIONS 6E2-133
CHART C-20
INDUCTION AIR CONTROL PLATE SYSTEM CHECK
AIR CONTROL SOLENOID.
• CONNECT VACUUM
GAGE TO HOSE.
• WITH ENGINE IDLING, VACUUM SHOULD BE AT LEAST 10" VACUUM.
~
I NOT OK I
I • CONNECT VACUUM PUMP WITH GAGE TO REPAIR VACUUM SOURCE I ENGINE MANIFOLD SIDE OF SOLENOID.
• IGNITION "ON", ENGINE "OFF".
• APPLY VACUUM AND OBSERVE VACUUM ACTUATOR LINKAGE.
• LINKAGE SHOULD NOT MOVE. DOES IT?
~ ~ • IGNITION "ON" ENGINE "OFF". • DISCONNECT SOLENOID ELECTRICAL ® • GROUND DIAGNOSTIC TEST TERMINAL (JUMPER CONNECTOR. DATA LINK CONNECTOR 1 TO 3). • REPEAT TEST. • APPLY VACUUM AGAIN WHILE OBSERVING • LINKAGE SHOULD MOVE. DOES IT?
LINKAGE.
L • LINKAGE SHOULD NOT MOVE.
~ ~ I MOVED I DID NOT MOVE I
I WHT /BLU SHORTED TO I FAULTY VACUUM SWITCH I GROUND VALVE
NO PROBLEM FOUND. OR SECONDARY INTAKE AIR FAUL TV ENGINE SYSTEM OK. CONTROL
MODULE (ECM)
• DISCONNECT SOLENOID ELECTRICAL
CONNECTOR.
• IGNITION
"ON", ENGINE "OFF".
• DIAGNOSTIC TEST TERMINAL GROUNDED. • CONNECT A TEST LIGHT ACROSS HARNESS
TERMINALS.
I LIGHT "ON" I LIGHT "OFF" I
I FAULTY
I
PROBE IGNITION FEED BLKIYEL WIRE WITH A SOLENOID TEST LIGHT CONNECTED TO GROUND.
I
l
LIGHT "ON" I LIGHT "OFF" j
I WHT/BLU WIRE IS OPEN, REPAIR OPEN IN BATTERY OR POSITIVE VOLTAGE FAUL TV CONNECTOR AT (BLKIYEL WIRE) CIRCUIT. ECM OR FAULTY ECM