Chart C-4-1 Misfire at Idle

Chart C-4-1:

Ignition Control Wiring:

CIRCUIT DESCRIPTION
The ignition system 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, resulting in a lower energy requirement to fire #4 spark plug. This leaves the remaining high voltage to fire #1 spark plug.


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

1. Monitoring "current weak cylinder" with a proper scan tool should isolate the problem cylinder when the misfire is occuring.

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 tower spark plug 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 C3-I module.