Mitsubishi Montero (2004+). Manual — part 395
IGNITION SYSTEM
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ENGINE ELECTRICAL
16-35
.
WAVEFORM OBSERVATION POINTS
Point A:
The height, length and slope of the spark line (refer to
abnormal waveform examples 1, 2, 3 and 4) show the fol-
lowing trends.
Point B:
SPARK LINE
PLUG
GAP
STATUS OF
ELECT-
RODES
COMPRES-
SION
FORCE
CONCENT-
RATION OF
AIR MIXTURE
IGNITION
TIMING
SPARK PLUG
CABLE
Length
Long
Small
Normal
Low
Rich
Advanced
Leak
Length
Short
Large
Large wear
High
Lean
Retarded
High
resistance
Height
High
Large
Large wear
High
Lean
Retarded
High
resistance
Height
Low
Small
Normal
Low
Rich
Advanced
Leak
Slope
Large
Plug is
fouled
−
−
−
−
AKX00279
kV
0
SECONDARY
IGNITION
VOLTAGE
WAVE PATTERN
TIME
NO.1 CYLINDER
NO.3 CYLINDER
IGNITION NOISE
NO.6 CYLINDER
IGNITION NOISE
NEUTRAL
SECTION
NO.4 CYLINDER
(WAVE PATTERN
IS DISTURBED)
NO.2 CYLINDER
IGNITION NOISE
NO.5 CYLINDER
IGNITION NOISE
AB
IGNITION SYSTEM
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ENGINE ELECTRICAL
16-36
Number of vibrations in reduction vibration section (Refer to
Abnormal Waveform Example 5)
Point C:
Number of vibrations at beginning of dwell section (Refer to
Abnormal Waveform Example 5)
Point D:
Ignition voltage height (distribution per each cylinder) shows
the following trends.
.
ABNORMAL WAVEFORMS EXAMPLES
Example 1
• Wave characteristics
Spark line is high and short.
• Cause of problem
Spark plug gap is too large.
Example 2
• Wave characteristics
Spark line is low and long, and is sloping.
Also, the second half of the spark line is distorted. This
could be a result of misfiring.
• Cause of problem
Spark plug gap is too small.
NUMBER OF VIBRATIONS
COIL AND CAPACITOR
Three or more
Normal
Except above
Abnormal
NUMBER OF VIBRATIONS
COIL
5
− 6 or higher
Normal
Except above
Abnormal
IGNITION
VOLTAGE
PLUG
GAP
CONDITION
OF ELECT-
RODE
COMPRESSION
FORCE
CONCENT-
RATION OF AIR
MIXTURE
IGNITION TIMING
SPARK PLUG
CABLE
High
Large
Large wear High
Lean
Retarded
High resistance
Low
Small
Normal
Low
Rich
Advanced
Leak
AKX00280
AKX00281
IGNITION SYSTEM
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ENGINE ELECTRICAL
16-37
Example 3
• Wave characteristics
Spark line is low and long, and is sloping. However,
there is almost no spark line distortion.
• Cause of problem
Spark plug gap is fouled.
Example 4
• Wave characteristics
Spark line is high and short.
Difficult to distinguish between this and abnormal wave
pattern example 1.
• Cause of problem
Spark plug cable is not properly connected. (Causing a
dual ignition)
Example 5
• Wave characteristics
No waves in wave damping section
• Cause of problem
Layer short in ignition coil.
AKX00282
AKX00283
AKX00284
IGNITION SYSTEM
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ENGINE ELECTRICAL
16-38
IGNITION PRIMARY VOLTAGE WAVE PATTERN
CHECK USING AN OSCILLOSCOPE
M1163004600086
.
MEASUREMENT METHOD
Required Special Tool:
MB991348: Test Harness Set
1. Disconnect the ignition power transistor connector and
connect the test harness set of the special tool (MB991348)
in between. All terminals should be connected.
2. When observing the number 1
− 4 cylinder group, connect
the primary pickup of the oscilloscope probe to ignition
power transistor side connector terminal (13).
For the number 2
− 5 cylinder group, connect to terminal
(12) and for the number 3
− 6 cylinder group, connect to
terminal (11).
3. Ground the primary pickup ground terminal.
4. Clamp the spark plug cable with the trigger pickup.
NOTE: Clamp the spark plug cable of cylinder number 1, 3
or 5 which belongs to the same group as the cylinder to
which the primary pickup is connected.
NOTE: The wave pattern of any cylinder in the same group
appears from the left side of the screen.
.
STANDARD WAVE PATTERN
Observation conditions
FUNCTION
SECONDARY
Pattern height
High (or low)
Pattern selector
Raster
Engine speed
Curb idle speed
AKX00285
11 12 13
PRIMARY
PICKUP
OSCILLOSCOPE
AB
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