spark plugs replace ISUZU TROOPER 1995 User Guide

6E2-42 DRIVEABILITV AND EMISSIONS
CHART A-3
(Page 1 of 3)
ENGINE CRANKS BUT WILL NOT RUN
Circuit Description:
Before using this chart, battery condition, engine cranking speed, and fuel quantity should be checked and verified
as being OK.
Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
CD A malfunction indicator lamp "ON" is basic test to determine if there is battery positive voltage and ignition
voltage supplied to the Engine Control Module (ECM). No data link connector data may be due to an ECM
problem. CHART A-2 will diagnose the ECM. If throttle position sensor voltage is over 2.5 volts, the engine
may be in the
"clear flood" mode, which will cause starting problems. The engine will not start without
reference pulses and, therefore, the "Scan tool" should indicate engine speed during cranking.
@ Because the electronic ignition system uses two plugs and wires to complete the circuit of each coil, the
opposite spark
should be left connected. If revolution per minute was indicated during crank, the ignition
control module is receiving a crank signal, but no spark at this test indicates the Ignition Control Module (ICM)
is not triggering the coils.
® The test light should blink, indicating the ECM is in control of the injectors. How bright the light blinks is not
important. However, the test light should be a J-34730-3 or equivalent.
@ This test will determine if the ignition control module is not generating the reference pules or if the wiring or
ECM are at fault. By touching and removing a test light to 12 volts on VEL/RED wire, a reference pulse should
be generated. If revolution per minute is indicated, the ECM and wiring are OK.
® High resistance in the spark plug wire could cause a "no start" condition. If a spark plug wire is found to be
faulty, replace it and retest system.
(SOHC)
I"M"
TOECM RED/GRN #1 BLU/YEL MAIN RED/GRN #2 BLU/YEL
RELAY
tRED/GRN
RED/GRN #3 BLU/YEL
RED/GRN #4 BLU/YEL
RED/GRN
#5 BLU/YEL
RED/GRN
#6 BLU/YEL
FUEL
INJECTORS ENGINE
CONTROL MODULE(ECM)
INJECTOR
RED/GRN
RED/GRN
RED/GRN
RED/GRN
RED/GRN
RED/GRN
IDOHCI BLU/YEL
BLU/YEL
l 1.3!l INJECTOR RESISTOR 1_
ORG/BLU
--+----
E~INE YEL/GRN D11 BLK/ORN -4>-BLK/YEL ----41sv---TO IGN BLK/RED -TOTACHOMETER SWITCH
BLK --:::L =
AND TCM (C91-D12)
CRANKSHAFT
POSITION
1 SENSOR
-........:::SHIELD
Fig. 6E2-26
•

DRIVEABILITV AND EMISSIONS 6E2-51
CHART A-7
(PJtge 1 of 3}
FUEL SYSTEM PRESSURE TEST
NOTE: FUEL SYSTEM IS UNDER PRESSURE. TO AVOID FUEL SPILLAGE, REFER TO FIELD SERVICE PROCEDURES FOR TESTING OR REPAIRS
REQUIRING DISASSEMBLY OF FUEL LINES OR FITTINGS. REFER TO~ 3 OF 3 OF THIS CHART.
CD • INSTALL FUEL PRESSURE GAUGE, J34730-1 OR EQUIVALENT, SEE CHART A-7 ~3 OF 3) FOR INSTALLATION PROCEDURE.
• DISCONNECT VACUUM HOSE FROM FUEL PRESSURE CONTROL VALVE.
• IGNITION MUST BE "OFF" FOR 10 SECONDS.
• TURN IGNITION "ON". FUEL PUMP SHOULD RUN FOR ABOUT 2 SECONDS.
• NOTE FUEL PRESSURE AFTER PUMP STOPS.
• FUEL PRESSURE SHOULD BE 280-320 kPa (41-46 PSI) AND HOLDING STEADY. IS IT?
I
• START AND IDLE ENGINE AT NORMAL OPERATING TEMPERATURE. • RECONNECT VACUUM LINE.
• FUEL PRESSURE SHOULD HAVE
DROPPED SLIGHTLY.
DID IT?
I
@ FUEL PRESSURE
WITHIN SPECIFICATION,
BUT NOT HOLDING.
• IGNITION "OFF".
.---'---$YES
-$r---'--NO -
@ • DISCONNECT VACUUM NO TROUBLE •
CONNECT FUSED
JUMPER FROM BATTERY POSITIVE
VOLTAGE TO FUEL PUMP
RELAY CONNECTOR BETWEEN THE BLK/RED WIRE AND RED/WHT WIRE IN ENGINE
COMPARTMENT.
HOSE FROM
FUEL FOUND. REFER PRESSURE CONTROL TO "DIAGNOSTIC
VALVE. AIDS" ON
• WITH ENGINE IDLING. FACING P.A@f. APPLY 12-14"
HYDRAGYRUM OF VACUUM TO FUEL PRESSURE CONTROL
VALVE
•
FUEL PRESSURE SHOULD DROP SLIGHTLY.
DID IT?
I
• GRADUALLY BLOCK FUEL PRESSURE LINE BY PINCHING FLEX HOSE.
• REMOVE JUMPER FROM
TEST CONNECTOR WHILE
CONTINUING TO BLOCK
PRESSURE LINE.
• PRESSURE SHOULD HOLD.
DID
IT?
I PRESSURE
OUT OF SPECIFICATION.
I USE,.eAef 2 OF THIS CHART.
I
INO I PRESSURE
I
I USE CHART I A-5
~~NLO------------------~ $~YELS---------------------, LOCATE AND CORRECT
CAUSE OF INTERRUPTED
MANIFOLD ABSOLUTE
PRESSURE SUPPLY TO
REGULATOR. FUEL PRESSURE
CONTROL VALVE ASSEMBLY
IS FAULTY.
• REPEAT ABOVE PROCEDURE CHECK FOR WHILE BLOCKING FUEL -LEAKING PUMP COUPLING HOSE. RETURN LINE INSTEAD OF -FAUL TV IN-TANK PUMP PRESSURE LINE BY PINCHING FLEX HOSE.
• PRESSURE SHOULD HOLD.
DID
IT?
LOCATE AND REPLACE LEAKING INJECTOR AND DRY SPARK PLUGS
FROM FLOODED
CYLINDERS.
FUEL PRESSURE
CONTROL VALVE
ASSEMBLY
IS FAULTY.

6E2-90 DRIVEABILITY AND EMISSIONS
INTERMITTENTS
Definition: Problem may or may not turn "ON" the
"Check Engine" malfunction indicator lamp or store
Diagnostic
Trouble Code (DTC).
DO NOT use the DTC charts in "Engine Components/
Wiring Diagrams/Diagnostic
Charts," Section "6E2-A"
for intermittent problem. The fault must be present to
locate the problem. If a fault is intermittent, use of DTC
charts may result in replacement of good parts.
•
• Most intermittent problems are caused by faulty
electrical
connections or wiring. Perform careful
visual/physical
check as described at start of
"Symptoms," Section "6E2-B." Check for:
Poor mating
of the connector halves. or
terminal not fully seated in the connector body
(backed out).
Improperly formed or damaged terminal. All
connector
terminals in the problem circuit
should be carefully reformed or replaced to
insure proper contact tension.
Poor
terminal to wire connection. This
requires removing the
terminal from the
connector body to check. Refer to
SECTION 8
"Wiring Harness Service,"
If a visual/physical check does not find the cause
of the problem, the car can be driven with a
voltmeter connected to a suspected circuit. A
"Scan tool" can also be used to help detect
intermittent conditions. An abnormal
voltage, or
"Scan" tool reading, when the problem occurs,
indicates the
problem may be in that circuit. If the wiring
and connectors check
OK, and a DTC was
stored
for a circuit having a sensor, except for
DTC(s) 44 and 45, substitute a known good sensor
and recheck.
• Loss of DTC memory. To check, disconnect
throttle position (TP) sensor and idle engine until
"Check
Engine" malfunction indicator lamp comes
"ON". DTC 21 should be stored, and kept in
memory when ignition is turned "OFF". If not, the
Engine
Control Module (ECM) is faulty.
•
An intermittent "Check Engine" malfunction
indicator
lamp with no stored DTC may be caused
by:
Ignition coil shorted to ground and arcing at
spark
plug wires or plugs.
"Check
Engine" malfunction indicator lamp
wire to ECM shorted to ground.
Diagnostic
"test" terminal wire to ECM,
shorted to ground.
ECM grounds, refer to ECM wiring diagrams.
• Check for an electrical system interference caused
by a defective
relay, ECM driven solenoid, or
switch. They can cause a sharp electrical surge.
Normally, the problem will occur when the faulty
component is operated.
• Check for improper installation of electrical
options such as lights, 2 way radios, etc.
• Ignition control wires should be routed away from
spark plug wires, electronic ignition (EI) wires, El
housing, coil and generator. Ground wire from
ECM to El should have a good connection.
• If problem has not been found, refer to "ECM
Connector Symptom" charts at the end of
"Symptoms," Section "6E2-B."
HARD START
Definition: Engine cranks OK, but does not start for a
long time. Does eventually run, or may
start
but immediately dies.
PRELIMINARY CHECKS
• Perform the careful visual/physical checks as
described at start of "Symptoms," Section "6E2-
B".
•
Make sure the driver is using the correct starting
procedure.
SENSORS
• CHECK: Engine coolant temperature sensor using
a
"Scan tool", compare engine coolant
temperature with ambient temperature
on
cold engine. -
If engine coolant temperature
readings
is 5 degrees greater than or less than
ambient air temperature on a
cold
engine, check resistance in engine
coolant temperature sensor circuit
or
sensor itself. Compare engine coolant
temperature sensor resistance value
to the "Diagnostic Aids" chart on
DTC
14 chart.
• CHECK: Manifold absolute pressure sensor.
Check for flooding and/or correct sensor
for vehicle.
• CHECK: TP sensor for binding or a high TP sensor
voltage with the throttle closed (should
read between 0.54 volt and 1.25 volts.)

FUEL SYSTEM
• CHECK:
• CHECK:
• CHECK:
• CHECK:
• CHECK:
• CHECK:
Fuel pump relay operation-pump should
turn "ON" for 2 seconds when ignition is
turned
"ON". Use CHART A-5.
Fuel injectors are correct for the vehicle.
Fuel
pressure, use CHART A-7.
Contaminated
fuel.
Engine fuse (visual inspect).
A
faulty in-tank fuel pump check valve will
allow
the fuel in the lines to drain back to
the tank after engine is stopped. To check
for this condition, perform fuel system
diagnosis CHART A-7.
IGNITION SYSTEM
• CHECK: For proper ignition voltage output with
spark tester J26792 or equivalent (ST-
125).
DRIVEABILITY AND EMISSIONS 6E2-91
• CHECK: Spark plugs. Remove spark plugs, check
for wet plugs, cracks, wear, improper
gap, burned electrodes, or heavy
deposits. Repair
or replace as necessary.
• CHECK: Bare or shorted wires.
• CHECK: Loose ignition coil ground.
ADDITIONAL CHECKS
• CHECK: Idle air control operation-use CHART C-
2C.
• CHECK: Basic engine problem. Refer to ENGINE
MECHANICAL DIAGNOSIS (SECTION
6A).
• CHECK: Service Bulletins for calibration updates.
SURGES AND/OR CHUGGLES
Definition: Engine power variation under steady
throttle or cruise. Feels like the car speeds
up and
slows down with no change in the
acceleration pedal.
PRELIMINARY CHECKS
• Perform the careful visual checks as described at
start
of "Symptoms," Section "6E2-B."
•
Be sure driver understands transmission
operation, and air conditioning compressor
operation
as explained in the owner's manual.
SENSORS
• CHECK: Heated oxygen sensor (H02S). The
H02S should respond quickly to different
throttle position, if it does not, check the
H02S for silicon or other contaminations
from fuel, or use of improper RTV sealant.
The sensor may have a white, powdery
coating and result in a high but false
signal voltage
(rich heated H02S signal
indication). The engine control module
will
then reduce the amount of fuel
delivered
to the engine, causing a severe
driveability problem. Also, watch for
green glycol contamination or cracking.
FUEL SYSTEM
• NOTICE: To determine ifthe condition is caused by
a rich
or lean system, the car should be
driven at the speed of the complaint.
Monitoring block learn will help identify a
problem.
Lean -Block learn above 142. Refer to
"Diagnostic Aids" on facing page of
diagnostic trouble code 44.
Rich -L.T. Fuel Trim above 118. Refer to
"Diagnostic Aids" on facing page of
diagnostic trouble code 45.
• CHECK: Fuel pressure while condition exists. Use
CHART A-7.
• CHECK: In-line fuel filter. Replace if dirty or
plugged.
IGNITION SYSTEM
• CHECK: For proper ignition voltage output using
spark tester (ST-125) J26792
or
equivalent .
• CHECK: Spark plugs. Remove spark plugs, check
for wet plugs, cracks, wear, improper
gap, burned electrodes, or heavy
deposits. Repair
or replace as necessary.
Also, check condition of electronic
ignition and spark plug wires.
• CHECK: Ignition timing. Using "Scan tool".
ADDITIONAL CHECKS
• CHECK: Engine control module grounds for being
clean, tight and in their proper location.
• CHECK: Vacuum lines for kinks or leaks.
• CHECK: Exhaust gas recirculation -There should
be no exhaust gas recirculation at idle.
Refer to CHART C-7.
• CHECK: Generator output voltage. Repair if less
than 9 or more than 16 volts.

IGNITION SYSTEM
• CHECK: Ignition timing, using a "Scan tool".
• CHECK: Ignition system; wires, plugs, electronic
ignition, etc.
ENGINE MECHANICAL
• CHECK: Perform a cylinder compression check.
See ENGINE MECHANICAL DIAGNOSIS
(SECTION 6).
• CHECK: For correct camshaft or weak valve
springs.
ADDITIONAL CHECKS
• CHECK: Manifold absolute pressure sensor.
Refer to
CHART C-10.
• CHECK: Throttle linkage for sticking or binding.
• CHECK: Park/neutral position switch circuit. See
CHART C-1A,
or use "Scan tool" and be
sure
tool indicates vehicle is in drive with
gear selector in drive or overdrive.
DRIVEABILITY AND EMISSIONS 6E2-95
• CHECK:
• CHECK:
• CHECK:
• CHECK:
• CHECK:
• CHECK:
Idle air control operation, use CHART C-
2C.
Exhaust gas recirculation valve. There
should be no exhaust gas recirculation at
idle. Refer to CHART C-7A.
Air conditioning (A/C) signal to engine
control module, "Scan tool" should
indicate A/C is being requested when
ever
A/C is selected. If problem exists
with A/C "ON," check A/C system
operation
CHART C-10.
Positive crankcase ventilation valve for
proper operation. Refer to "Positive
Crankcase Ventilation (PCV),"
Section
"6E2-C13."
For broken motor mounts.
Generator output
voltage. Repair if less
than 9 or more than 16 volts.
POOR FUEL ECONOMY
Definition: Fuel economy, as measured by an actual
road test, is noticeably lower than
expected.
Also, fuel economy is
noticeably lower than it was on this car at
one time,
as previously shown by an actual
road test.
PRELIMINARY CHECKS
• Perform the careful visual checks as described at
start
of "Symptoms," Section "6E2-B."
• Visually (physically)
check: Vacuum hoses for
splits, kinks, and proper connections as shown on
"Vehicle Emission Control Information" label.
• Check
owner's driving habits.
Is A/C "ON" full time (Defroster mode "ON")?
Are tires at correct pressure?
Are
excessively heavy loads being carried?
Is acceleration too much, too often?
• Check air cleaner filter for dirty or being plugged.
IGNITION SYSTEM
• CHECK: Ignition timing. Refer to "Vehicle
Emission Control Information" label.
• CHECK: Spark plugs. Remove spark plugs, check
for wet plugs, cracks, wear, improper
gap, burned electrodes, or heavy
deposits. Repair or
replace as necessary.
COOLING SYSTEM
• CHECK: Engine coolant level.
• CHECK: Engine thermostat for faulty part (always
open) or for wrong heat range. Refer to
ENGINE COOLING (SECTION 68).
ENGINE MECHANICAL
• CHECK: Compression. See ENGINE MECHANICAL
DIAGNOSIS
(SECTION 6A).
ADDITION CHECKS
• CHECK:
• CHECK:
• CHECK:
• CHECK:
• CHECK:
TCC operation (A/T). Use CHART C-8. A
"Scan tool" should indicate a revolution
per minute drop, when the TCC is
commanded
"ON".
For exhaust system restriction.
For proper
calibration of speedometer.
Induction system and crankcase for air
leaks.
Fuel
injectors are correct for the vehicle.

6E2-96 DRIVEABILITY AND EMISSIONS
EXCESSIVE EXHAUST EMISSIONS OR ODORS
Definition: Vehicle fails an emission test. Vehicle has
excessive
"rotten egg" smell. Excessive
odors
do not necessarily indicate
excessive emissions.
PRELIMINARY CHECKS
• Perform on-board diagnostic system check.
• IF EMISSION TEST shows excessive CO and
hydrocarbon check items which cause car to run
RICH (Long Term Fuel Trim less than 118), refer to
"Diagnostic Aids" on facing page of diagnostic
trouble code (DTC) 45.
• If EMISSION TEST shows excessive NOx, check
items which cause car
to run lean or too hot.
COOLING SYSTEM
• If the "Scan tool" indicates a very high engine
coolant temperature and the system is running
lean:
CHECK: Engine coolant level
CHECK: Engine thermostat for faulty part
(always open) or for wrong heat range. Refer
to
ENGINE COOLING (SECTION 68).
CHECK: Cooling fan operation.
FUEL SYSTEM
• NOTICE: If the system is running rich (L.T. Fuel
Trim near 118), refer to "Diagnostic Aids"
on facing page
of DTC 45.
-
If the system is running lean (L.T. Fuel
Trim near 142) refer to "Diagnostic
Aids" on facing page of DTC 44.
• CHECK: For properly installed fuel cap.
• CHECK: Fuel pressure. Use CHART A-7.
• CHECK: Canister for fuel loading. Refer to
"Evaporative Emission Control System,"
Section
"6E2-C3."
IGNITION SYSTEM
• CHECK: Ignition timing. Refer to "Vehicle
Emission Control Information" label.
• CHECK: Spark plugs, plug wires, and ignition
components. Refer to
ENGINE
ELECTRICAL (SECTION 6D).
ADDITIONAL CHECKS
• CHECK: For vacuum leaks.
• CHECK: Exhaust gas recirculation valve for not
opening. Use CHART C-7.
• CHECK: For lead contamination of three way
catalytic converter (look for the removal
of fuel filler neck restrictor).
• CHECK: Carbon build-up. Remove carbon with
top engine cleaner. Follow instructions
on can.
• CHECK: PCV valve for being plugged, stuck or
blocked PCV hose or fuel in the
crankcase.
BACKFIRE
Definition: Fuel ignites in intake manifold, or in
exhaust system, making
loud popping
noise.
PRELIMINARY CHECKS
• Perform the careful visual/physical checks as
described at start of "Symptoms," Section "6E2-
B."
IGNITION SYSTEM
• CHECK: Proper ignition coil output voltage with
spark tester J26792 or equivalent (ST-
125).
• CHECK: Spark plugs. Remove spark plugs, check
for
wet plugs, cracks, wear, improper
gap, burned
electrodes, or heavy
deposits. Repair
or replace as necessary.
• CHECK: Spark plug wires for crossfire, also
inspect electronic ignition, spark plug
wires, and proper routing of plug wires.
• CHECK: Ignition timing. Refer to "Vehicle
Emission Control Information" label.
• CHECK: If an intermittent condition exists in the
ignition system, see
"Ignition System/
IGNITION CONTROL," Section "6E2-C4"
or ENGINE ELECTRICAL (SECTION 6D).
ENGINE MECHANICAL
• CHECK: Compression- Look for sticking or leaking
valves.
• CHECK: Valve timing, refer to ENGINE
MECHANICAL DIAGNOSIS (SECTION
6A).
• CHECK: Intake and exhaust manifold passages for
casting
flash.
FUEL SYSTEM
• CHECK: Perform fuel system diagnosis check, see
CHART A-7.

6E2-142 DRIVEABILITY AND EMISSIONS
CHART C-40-1
ELECTRONIC IGNITION (EI) MISFIRE AT IDLE
Circuit Description:
The electronic ignition system uses a waste spark method of distribution. For example, in this type of system the
ignition
control module triggers the #1 /4 coil pair resulting in both #1 and #4 spark plugs firing at the same time
# 1
cylinder is on the compression stroke at the same time #4 is on the exhaust stroke, resulting in a lower energy
requirement
to fire #4 spark plug. This leaves the remainder of the high voltage to be used to fire # 1 spark plug.
On this vehicle, the crankshaft position sensor is mounted to the engine block and protrudes through the block to
within approximately .05" ofthe crankshaft reluctor. Since the reluctor is a machined portion ofthe crankshaft and
the crankshaft position sensor is mounted in a fixed position on the
block, timing adjustments are not possible or
necessary.
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
CD If the "Misfire" complaint exists under load only, the diagnostic chart on page 2 must be used. Engine speed
should drop approximately equally on all plug leads.
® A spark test such as a ST-125 must be used because it is essential to verify adequate available secondary
voltage at the spark plug. (25,000 volts).
@ If the spark jumps the test gap after grounding the opposite plug wire, it indicates excessive resistance in the
plug which was Bypassed. A faulty or poor connection at that plug could also result in the miss condition.
Also, check for carbon deposits inside the spark plug boot.
@ If carbon tracking is evident, replace coil and be sure plug wires relating to that coil are clean and tight.
Excessive
wire resistance or faulty connections could have caused the coil to be damaged.
@ If the no spark condition follows the suspected coil, that coil is faulty; otherwise, the ignition control module is
the cause
of no spark. This test could also be performed by substituting a known good coil for the one causing
the no spark condition.
ENGINE HARNESS
COIL ASSEMBLIES IGNITION CONTROL MODULE CONNECTOR
1-- - - -(GREEN)
~ '--1-1 -+---,
I
:TI
:D
r---------~~----------YE~GRN
~--------~~-------------VEL ' BLKJORN -----4---+-TO TACHOMETER & •
TCM (C91-D12) OPEN ! ' r---------~~----------YE~RED
r-----------<1~----------YEL!BLK ' BLKJRED ___..,TO IGN COIL FUSE
IAsiAsl;rJIA21A 1!
6-WAY ICM
CONNECTOR
Fig. 6E2-89
CRANKSHAFT
POSITION
SENSOR
lc0§,1
2-WAY ICM
CONNECTOR ENGINE
CONTROL
MODULE
(ECM)
BYPASS IGNITION CONTROL
SIGNAL
REF HIGH
REF LOW
IB!IB2I~1I
3-WAY ICM CONNECTOR

DRIVEABILITV AND EMISSIONS 6E2-143
CHART C-40
ELECTRONIC IGNITION (EI) MISFIRE AT IDLE
CD • IF ENGINE MISFIRES UNDER LOAD ONLY, SEE CHART C-4D-2. • ENGINE IDLING AT NORMAL OPERATING TEMPERATURE, DISCONNECT IDLE AIR CONTROL. • MOMENTARILY DISCONNECT EACH SPARK PLUG LEAD, USING INSULATED PLIERS,
WHILE OBSERVING ENGINE SPEED. SEE CAUTION*. • ALL PLUG LEAD(S) SHOULD RESULT IN A REVOLUTION PER MINUTE DROP. DID THEY?
$ $
•
WITH IGNITION "OFF", INSTALL SPARK TESTER (ST-125) J-26792 OR I SEE "ROUGH, UNSTABLE OR INCORRECT IDLE
EQUIVALENT ON PLUG LEAD(S) WHOSE REMOVAL DID NOT RESULT IN OR STALLING" IN SYMPTOMS Si€'FISN "B". REVOLUTION PER MINUTE DROP. • SPARK SHOULD JUMP TESTER GAP WHILE CRANKING ENGINE. DOES IT?
$ $
•
WITH IGNITION "OFF", GROUND THE OPPOSITE PLUG CHECK FOR: @
LEAD OF THE AFFECTED COIL AT SPARK PLUG. -
FAUL TV, WORN OR CRACKED SPARK PLUG(S). • SPARK SHOULD JUMP TESTER GAP WHILE CRANKING -PLUG FOULING DUE TO ENGINE MECHANICAL FAULT. ENGINE. DOES IT? IF SPARK PLUGS CHECK OUT OK, REFER TO "CUTS
OUT, MISSES" IN SYMPTOMS SiC'flet~ "B".
~ $
• CHECK THE RESISTANCE OF EACH PLUG WIRE OF THE REPLACE
THE SPARK PLUG FOR THE LEAD WHICH WAS COIL WHICH DID NOT FIRE THE SPARK TESTER. JUMPERED TO GROUND. IF MISFIRE
IS STILL PRESENT, • WIRE RESISTANCE SHOULD BE LESS THAN 30,000 START MISFIRE TEST AGAIN AT STEP 1. OHMS EACH AND WIRES SHOULD NOT BE GROUNDED.
ARE WIRES OK?
$ $
• REMOVE COIL RETAINING NUTS AND REMOVE COILS.
I
REPLACE FAUL TV WIRE(S).I
• COILS SHOULD BE FREE OF CARBON TRACKING. ARE THEY?
$ $
•
SWITCH A NORMALLY OPERATING COIL WITH THE REPLACE IGNITION
COIL. ALSO CHECK FOR COIL FROM PROBLEM CYLINDER. FAULTY PLUG WIRE CONNECTION(S) AND • SPARK SHOULD JUMP TESTER GAP AT PROBLEM WIRE NIPPLE(S) FOR CARBON TRACKING.
CYLINDER WHILE CRANKING ENGINE. DID IT?
$ $
ORIGINAL IGNITION
I
REPLACE ELECTRONIC IGNITION MODULE. COIL IS FAUL TV.
*CAUTION: When handling secondary spark plug leads with engine running, insulated pliers must be used and care exercised to
prevent a possible electrical shock.
CLEAR DIAGNOSTIC TROUBLE CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NORMAL "CHECK ENGINE" MALFUNCTION
INDICATOR LAMP OPERATION.

6E2-144 DRIVEABILITY AND EMISSIONS
CHART C-40-2
ELECTRONIC IGNITION (EI) MISFIRE UNDER LOAD
Circuit Description:
The electronic ignition system uses a waste spark method of distribution. For example, in this type of system the
ignition
control module triggers the # 1/4 coil pair resulting in both # 1 and #4 spark plugs firing at the same time
# 1 cylinder is on the compression stroke at the same time #4 is on the exhaust stroke, resulting in a lower energy
requirement
to fire #4 spark plug. This leaves the remainder of the high voltage to be used to fire #1 spark plug.
On this application, the crankshaft position sensor is mounted to the engine block and protrudes through the block
to within approximately 050" of the crankshaft reluctor. Since the reluctor is a machined portion of the crankshaft
and the crankshaft position sensor is mounted in a fixed position on the
block, timing adjustments are not possible
or necessary.
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
CD If the "Misfire" complaint exists at idle only, the diagnostic chart on page 1 must be used. A spark tester such
as a ST-125 must be used because it is essential to verify adequate available secondary voltage at the spark
plug. (25,000 volts). Spark should jump the test gap on all 4 leads. This simulates a "load" condition.
® If the spark jumps the test gap after grounding the opposite plug wire, it indicates excessive resistance in the
plug which was Bypassed. A faulty or poor connection at that plug could also result in the miss condition.
Also, check for carbon deposits inside the spark plug boot.
® If carbon tracking is evident, replace coil and be sure plug wires relating to that coil are clean and tight.
Excessive
wire resistance or faulty connections could have caused the coil to be damaged.
® If the no spark condition follows the suspected coil, that coil is faulty, otherwise, the ignition control module is
the cause
of no spark. This test could also be performed by substituting a known good coil for the one causing
the no spark condition.
COIL ASSEMBLIES IGNITION CONTROL MODULE
ENGINE HARNESS
CONNECTOR
(GREEN) -----
:TI '--+I -l-----,
I
:TI
~
~--------~~-----------YE~GRN
~--------~~--------------VEL ' BLK/RED ------«--TO TACHOMETER &
OPEN ' TCM (C91-D12)
~--------~~-----------YE~RED
1------------((-----------YE~BLK ' BLK/ORN_.' TO IGN COIL FUSE
ENGINE SPEED
1 SENSOR
~SHIELD
IAsiAsii4ibiA21A11
6-WAY ICM
CONNECTOR
Fig. 6E2-90
lcik,l
2-WAY ICM
CONNECTOR ENGINE
CONTROL
MODULE(ECM)
BYPASS
IGNITION CONTROL
SIGNAL
REF HIGH
REF LOW
I
BJIB2I~1I
3-WAY ICM
CONNECTOR
•

DRIVEABILITV AND EMISSIONS 6E2-145
CHART C-40-2
ELECTRONIC IGNITION (EI) MISFIRE UNDER LOAD
CD • IF ENGINE MISFIRES AT IDLE ONLY, SEE CHART C-4D-1. • IGNITION "OFF"
• DISCONNECT ONE SPARK PLUG LEAD AT A TIME AND,
INSTALL SPARK TESTER (ST-125) J-26792 OR EQUIVALENT.
• OBSERVE SPARK TESTER WITH ENGINE IDLING. REPEAT THIS TEST FOR ALL PLUG LEADS. SEE CAUTION* • SPARK SHOULD JUMP TESTER GAP ON ALL LEADS, WITH
ENGINE IDLING, DID IT?
~ $
• WITH IGNITION "OFF", GROUND THE OPPOSITE PLUG CHECK FOR: LEAD OF THE AFFECTED COIL AT SPARK PLUG. -
FAUL TV, WORN OR CRACKED SPARK PLUG(S). • SPARK SHOULD JUMP TESTER GAP WHILE CRANKING -PLUG FOULING DUE TO ENGINE MECHANICAL FAULT. ENGINE. DOES IT? IF SPARK PLUGS CHECK OUT OK, SEE "CUTS OUT,
MISSES" IN SYMPTOMS SEe'l'tO'I'Q' "B".
~ $
• CHECK THE RESISTANCE OF EACH PLUG WIRE OF THE COIL REPLACE THE SPARK PLUG FOR THE LEAD WHICH
WHICH DID NOT FIRE THE SPARK TESTER. WAS JUMPERED TO GROUND. IF MISFIRE IS STILL
• WIRE RESISTANCE SHOULD BE LESS THAN 30,000 OHMS EACH PRESENT, START MISFIRE TEST AGAIN AT STEP 1. AND WIRES SHOULD NOT BE GROUNDED. ARE WIRES OK?
~ $
• REMOVE COIL RETAINING NUTS AND REMOVE COILS. REPLACE FAUL TV WIRE(S). I ® • COILS SHOULD BE FREE OF CARBON TRACKING. ARE THEY?
$ $
• SWITCH A NORMALLY OPERATING COIL WITH REPLACE IGNITION COIL. ALSO CHECK FOR THE COIL FROM PROBLEM CYLINDER. FAUL TV PLUG WIRE CONNECTION(S) AND • SPARK SHOULD JUMP TESTER GAP WITH WIRE
NIPPLE(S) FOR CARBON TRACKING.
ENGINE IDLING. DID IT?
:r ~ ORIGINAL IGNITION
I
REPLACE ELECTRONIC IGNITION MODULE. COIL IS FAUL TV.
*CAUTION: When handling secondary spark plug leads with engine running, insulated pliers must be used and care exercised to prevent a possible electrical shock.
CLEAR
DIAGNOSTIC TROUBLE CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NORMAL "CHECK ENGINE" MALFUNCTION
INDICATOR LAMP OPERATION.