Chart C-4F-1 C(3)I Misfire At Idle (VIN 7)

CHART C-4F-1

C(3)I MISFIRE AT IDLE

1986-1987 3.8L TURBO (VIN 7) (PORT)
Circuit Description:
The C(3)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.

CHART C-4F-1C(3)I MISFIRE AT IDLE 1986-1987 3.8L TURBO (VIN 7) (PORT):

Test Description: Numbers below refer to circled numbers on the diagnostic chart.
1. If the "misfire" complaint exists under load only, diagnostic CHART C-4F-2 must be used. Engine rpm should drop approximately equally on all plug leads.
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.). Secondary voltage of at least (25,000 volts) must be present to jump the gap of a ST-125.
3. If ignition coils are carbon tracked, the coil tower spark plug wire nipples may be damaged.
4. By checking the secondary resistance, a coil with an open secondary may be located.
5. 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 C(3)I module.