Chart C-4-1 Misfire at Idle

Ignition System Circuit Diagram (Type II):

Chart C-4-1, Misfire At Idle (Type II Ignition):

CIRCUIT DESCRIPTION:

The C3I uses a waste spark method of spark distribution. In this type of ignition system the ignition module triggers the #1/4 coil pair resulting in both #1 and #4 spark plugs firing at the same time. #1 cylinder is on the compression stroke at the same time #4 is on the exhaust stroke and vise/versa.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. If the "misfire" complaint exists under load only, Refer to Chart C-4-2, Misfire Under LoadChart C-4-2 Misfire Under Load.
2. A spark tester such as a ST-125 must be used because it is essential to verify adequate available secondary voltage at the spark plug (25,000 volts).
3. If ignition coils are carbon tracked, the coil towers, spark plug wires, or wire boots may be damaged.
4. By checking the secondary resistance, a coil with an open secondary may be located.
5. By installing a normally operating coil pack, a determination can be made as to fault being the coil or C3I module.