Bad Scope Pattern

Figure 12 - Secondary Side (Parade):

Ignition voltage too high/burn time shorter (arrows).

Test condition: can occur at any engine rpm with or without load.

Cause:
- Spark plug electrode gap too large,
- Additional spark paths on secondary side,
- Fuel/air mixture too lean.

Figure 13 - Secondary Side (Parade):

Ignition voltage too low/combustion time longer.

Test condition: can occur at any engine rpm with or without load.

Cause:
- Spark plug gap too small,
- Fuel/air mixture too rich,
- Loss of compression.

Figure 14 - Secondary Side (Parade):

Decay process too high.

Test condition: Accelerate engine repeatedly up to approx. 3000 rpm or operate engine under load on dynamometer.

Cause: Fuel/air mixture too lean at one cylinder (arrows).

NOTE: If engine is not running smoothly (not running on all cylinders) after start up, the engine should be turned off at normal operating temperature and started again after a cool off period (approx. 15 min.) to allow a better diagnosis. When re-starting, note test condition.

Malfunction may only occur momentarily.

Figure 15 - Secondary Side (Parade):

Test condition: can occur at any engine rpm with or without load.

Cause: Spark plug fouled by carbon, oil (arrow), excessive resistance at secondary side.

Figure 16 - Secondary Side (Parade):

Test condition: can occur at any engine rpm with or without load.

Cause: Excessive resistance at secondary side (ignition cable 4, distributor rotor, ignition coil, or high voltage output).

Figure 17 - Secondary Side (Single Display):

Test condition: starting rpm.

Cause: Ignition coil, voltage terminal 15, terminal 1.

NOTE: Engine does not start (engine not running).

Figure 18 - Secondary Side (Single Display):

No decay process.

Test condition: cranking rpm.

Cause: Ignition coil or DI module.

NOTE: Engine does not start (engine not running).

Figure 19 - Secondary Side (Single Display):

Test condition: can occur at any engine RPM with or without load.

Engine running.

Cause: Ignition coil or DI module.

Figure 20 - Secondary Side (Parade):

Too few oscillations.

Test condition: can occur at any engine rpm with or without load.

Cause: Ignition coil or control module.

Figure 21 - Secondary Side (Parade):

Test condition: cranking rpm.

Cause: Ignition coil.

NOTE: Engine does not start (engine not running).

Figure 22 - Secondary Side (Parade):

Decay process too high.

Test condition: Accelerate engine repeatedly up to approximately 3000 rpm or operate engine under load on dynamometer.

Cause: Fuel/air mixture too lean at all cylinders.

Figure 23 - Secondary Side (Parade), 12 Cylinder:

Test condition: Can occur at any engine rpm.

Cause: Spark plug connector, ignition wire defective.

NOTE: Engine does not run smoothly.

Figure 24 - Secondary Side (Parade), 12 Cylinder:

Retarded ignition angle of cylinders 1-6.

Test condition: Can occur at any engine rpm.

Cause:
Vacuum line on DI control module for cylinders 1-6 defective or not connected.
DI control module defective.

Figure 25 - Secondary Side (Single Display), 12 Cylinder:

Test condition: Can occur at any engine rpm.

Engine runs rough at idle

Cause: Spark plug connector, ignition wire defective.