[16] ENGINE ELECTRICAL - - IGNITION SYSTEM - ON-VEHICLE SERVICE - IGNITION SECONDARY VOLTAGE WAVEFORM CHECK USING AN OSCILLOSCOPE <4G6-SOHC, 4G6-DOHC> | PRINT PAGE / INDEX / PRIOR / NEXT

| IGNITION SECONDARY VOLTAGE WAVEFORM CHECK USING AN OSCILLOSCOPE <4G6-SOHC, 4G6-DOHC>
| MEASUREMENT METHOD Clamp the secondary pickup around the spark plug cable. NOTE: The peak ignition voltage will be reversed when the spark plug cables No. 2 and No. 4, or No. 1 and No. 3 cylinders are clamped. Because of the two-cylinder simultaneous ignition system, the waveforms for two cylinders in each group appear during waveform observation (No. 1 cylinder - No. 4 cylinder, No. 2 cylinder - No. 3 cylinder). However, waveform observation is only applicable for the cylinder with the spark plug cable clamped by the secondary pickup. Identifying which cylinder waveform is displayed can be difficult. For reference, remember that the waveform of the cylinder attached to the secondary pickup will be displayed as stable. Clamp the spark plug cable with the trigger pickup. NOTE: Clamp the trigger pickup to the same spark plug cable clamped by the secondary pickup.
STANDARD WAVEFORM
Observation Conditions
Function | Secondary
--- | ---
Pattern height | High (or Low)
Pattern selector | Raster
Engine revolutions | Curb idle speed
Observation Conditions (The only change from above condition is the pattern selector.)
Pattern selector | Display
WAVEFORM OBSERVATION POINTS
Point A: The height, length and slope of the spark line show the following trends (Refer to abnormal waveform examples, 1, 2, 3 and 4).
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
Short | Large | Large wear | High | Lean | Retarded | High resistance
Height | High | Large | Large wear | High | Lean | Retarded | High resistance
Low | Small | Normal | Low | Rich | Advanced | Leak
Slope | Large | Plug is fouled | - | - | - | -
Point B: Number of vibration in reduction vibration section (Refer to abnormal waveform example 5)
Number of vibrations | Coil and condenser
--- | ---
3 or more | Normal
Except above | Abnormal
Point C: Number of vibrations at beginning of dwell section (Refer to abnormal waveform example 5)
Number of vibrations | Coil
--- | ---
5 - 6 or higher | Normal
Except above | Abnormal
Point D: Ignition voltage height (distribution per each cylinder) shows the following trends.
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
| EXAMPLES OF ABNORMAL WAVEFORMS
| 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. Difficult to distinguish between this and abnormal waveform example 1. Cause of problem Spark plug cable is nearly falling off (Causing a dual ignition).
| Example 5 Wave characteristics No waves in wave damping section. Cause of problem Layer short in ignition coil.

[16] ENGINE ELECTRICAL - - IGNITION SYSTEM - ON-VEHICLE SERVICE - IGNITION SECONDARY VOLTAGE WAVEFORM CHECK USING AN OSCILLOSCOPE <4G6-SOHC, 4G6-DOHC> | PRINT PAGE / INDEX / PRIOR / NEXT

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