Chart C-4C-2 Misfire Under Load

Chart C-4C-2 Ignition System Check:

Wiring Diagram for Chart C-4C-1 Ignition System Check:

CHART C-4C-2 C3-I MISFIRE UNDER LOAD


Circuit Description:
The C3-I 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. If the "misfire" complaint exists at idle only, diagnostic CHART C-4C-1 must be used.

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). Spark should jump the tester gap on all 6 leads. This simulates a "load" condition.


3. If ignition coils are carbon tracked, the coil tower spark plug wire nipples may be damaged.

4. By switching a normally operating coil into the position of the malfunctioning one, a determination can be made as to fault being the coil or C3-I module.