Mitsubishi Eclipse. Manual - part 675

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-43

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.

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.

NUMBER OF VIBRATIONS

COIL

5 

− 6 or higher

Normal

Except above

Abnormal

IGNITION 
VOLTAGE

PLUG 
GAP

CONDITION 
OF 
ELECTRODE

COMPRESSION 
FORCE

CONCENTRATION 
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

AKX00282

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-44

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.

<3.0L ENGINE>

.

MEASUREMENT METHOD
1. Clamp the spark plug cable of the number 1 cylinder with the 

secondary pickup and check the wave patterns for each 
cylinder.

2. Connect the secondary pickup to the other cylinder in turn 

and check the wave patterns for each cylinder.

.

STANDARD WAVE PATTERN

AKX00283

AKX00284

Observation Conditions 

FUNCTION

SECONDARY

Pattern height

High (or low)

Pattern selector

Raster

Engine speed

Curb idle speed

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-45

.

WAVEFORM OBSERVATION POINTS
NOTE:  Abnormal waveform examples are shown subse-
quently.
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.

AKX00278

kV

0

SECONDARY

IGNITION

VOLTAGE

WAVE PATTERN

IGNITION VOLTAGE
(POINT D)

SPARK LINE (POINT A)

DWELL SECTION

WAVE DAMPING REDUCTION SECTION (POINT B)

POINT C

TIME

AB

SPARK LINE

PLUG 
GAP

CONDITION 
OF 
ELECTRODE

COMPRESSION 
FORCE

CONCENTRATION 
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 −

−

−

−

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-46

Point B: 

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 
ELECTRODE

COMPRESSION 
FORCE

CONCENTRATION 
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