Mitsubishi Eclipse / Eclipse Spyder (2000-2002). Service and repair manual - part 367

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-45

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.

IGNITION PRIMARY VOLTAGE WAVE PATTERN 
CHECK

M1163004600020

<3.0L ENGINE>

MEASUREMENT METHOD
1. Disconnect the distributor connector and connect special 

tool (Test harness: MB991348) in between. (All of the 
terminals should be connected.)

2. Connect the analyzer primary pickup to the distributor 

connector terminal 2.

3. Connect the primary pickup ground terminal.

4. Clamp the spark plug cable with the trigger pickup.

NOTE: The wave pattern of the cylinder clamped to the 
trigger pickup will appear at the left edge of the screen.

AKX00282

AKX00283

AKX00284

AKX01282

OSCILLOSCOPE

PRIMARY
PICKUP

GROUND

1 2 3 4 5 6 7

AB

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-46

STANDARD WAVE PATTERN

OBSERVATION CONDITIONS 

FUNCTION

SECONDARY

Pattern height

High (or low)

Pattern selector

Raster

Engine speed

Curb idle speed

OBSERVATION CONDITIONS 

Pattern selector

Display

Pattern height

High (or low)

Engine speed

Curb idle speed

AKX00286

PRIMARY
VOLTAGE
WAVE PATTERN

(V)

100

0

ZENER
VOLTAGE
(POINT C)

(APPROXIMATELY
40

~

10V)

DWELL SECTION

SPARK LINE
(POINT A)

WAVE DAMEPING REDUCTION
SECTION(POINT B)

TIME

AB

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-47

WAVEFORM OBSERVATION POINTS

NOTE:  Abnormal waveform examples are shown 
subsequently.
Point A: 

The height, length and slope of the spark line (refer to 
abnormal waveform examples 1, 2, 3 and 4) show the 
following trends.

Point B: 

Number of vibrations in reduction vibration section (Refer to 
Abnormal Waveform Example 5)

Point C: 

Height of Zener voltage

AKX01284

(V)

10

0

IGNITION PRIMARY
VOLTAGE 
WAVE PATTERN

CENTER 
SECTION

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

-

-

-

-

NUMBER OF VIBRATIONS

COIL, CAPACITOR

Three or higher

Except above

Normal

Abnormal

IGNITION SYSTEM

TSB Revision

ENGINE ELECTRICAL

16-48

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.

Example 4

•

Wave characteristics
Spark line is high and short

•

Cause of problem
Spark plug cable is not properly connected. (Causing a 
dual ignition)

HEIGHT OF ZENER 
VOLTAGE

PROBABLE CAUSE

High

Problem in zener diode

Low

Abnormal resistance in 
primary coil circuit

AKX00288

AKX00289

AKX00290

AKX00291