compression ratio ISUZU TROOPER 1995 User Guide

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.

6E2-138 DRIVEABILITY AND EMISSIONS
SECTION C4
ELECTRONIC IGNITION (EI) SYSTEM/IGNITION CONTROL (IC)
CONTENTS
General Description . . . . . . . . . . . . . . . . . . . . . 6E2-138
Purpose
............................ 6E2-138
Operation
........................... 6E2-138
Results of Incorrect Operation . . . . . . . . . . . 6E2-139
How diagnostic trouble code (DTC) 42 is
Determined ........................ 6E2-139
Diagnosis. . . . . . . . . . . . . . . ............. 6E2-139
Diagnostic
trouble code (DTC) 12 . . . . . . . . . 6E2-139
On-Vechicle Service . .

. . . . . . . . . . . . . . . . . . . 6E2-139
Electronic Ignition (EI) Assembly .......... 6E2-139
Crankshaft Position (CKP) Sensor ......... 6E2-140
Ignition Coil
.......................... 6E2-140
Ignition Control
Module (ICM) ............ 6E2-140
Ignition
Timing ....................... 6E2-140
Chart
C-4D-1 Electronic Ignition (EI) misfire
at
Idle .............................. 6E2-142
Chart C-4D-2 Electronic Ignition (EI) misfire
Under Load .......................... 6E2-144
GENERAL DESCRIPTION
PURPOSE
The Electronic Ignition (EI) system controls fuel
combustion by providing a spark to ignite the
compressed
air/fuel mixture at the correct time. To
provide improved engine performance,
fuel economy,
and
control of exhaust emissions, the Engine Control
Module
(ECM) controls spark advance timing with the
Ignition Control (IC) system.
OPERATION
The "EI" is a "waste spark" system in which 2 plugs are
fired
simultaneously from one coil. The spark plugs are
paired
to a coil, so that when both fire, one cylinder is
on the compression stroke and the other is on exhaust.
There is
Iitie resistance across the plug gap on the
exhaust stroke, so the
plug requires very little voltage
to fire, thereby providing the other plug (compression)
with maximum available voltage.
The system uses a magnetic Crankshaft Position (CKP)
sensor which protrudes into the block, within
approximately .050" of the crankshaft reluctor. The
reluctor is a special wheel cast on the crankshaft that
has seven machined
slots, six of which are equally
spaced 60° apart). The seventh slot is spaced 1 oo from
one
of the other slots. As the reluctor rotates with the
crankshaft, the
slots change the magnetic field of the
sensor, causing
an induced voltage pulse.
By counting the time between pulses, the Ignition
Control Module (ICM)
can recognize the pulse of the
seventh
slot (sync pulse). Based on this sync pulse, the
module sends the reference signal to the ECM to
calculate CKP (used to fire coils in correct sequence)
and engine speed.
To
properly control timing, the ECM relies on the
following information:
• Engine load (manifold absolute pressure or
vacuum).
• Atmospheric (barometric) pressure.
• Engine temperature.
• Intake air temperature.
• CKP
• Engine speed (revolution per minute).
The ignition
control system consisits of the "EI"
assembly (coils, module,
and CKP sensor), ECM and
connecting wires. These circuits
perform the following
functions:
• "EI" reference
The CKP sensor sends a signal to the ICM which
generates a reference
pulse which is sent to the
ECM. The ECM uses this signal to calculate CKP
and engine speed (also used to trigger the
injector).
• Reference ground (GND)
This wire is GNd through the module and makes
sure the GNd circuit has no
voltage drop between
the
ICM and the ECM, which if open, could affect
performance.
• Bypass
At about 400 revolution per minute, the ECM
applies 5 volts to this circuit to switch spark timing
control from the ICM to the ECM. An open or
grounded bypass circuit
will set a diagnostic
trouble code 42 and the engine will run at base
timing,
plus a small amount of advance built into
the
ICM.
• IGNITION CONTROL (IC)
The ECM uses this circuit (when bypass voltage is
applied) to trigger the "EI" module. The ECM uses
the
CKP to base its calculation of the amount of
spark advance needed under present engine
conditions.
•