Pontiac Fiero 1988 Service Manual page 555

6E2-C4-8 DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI)
POWER / GROUND
CONNECTOR
-MB
6-WAY IGN.
MODULE
CONNECTOR
11-21-86
0
O
MODULE / COIL
ASSEMBLY
COIL
ASSEMBLIES
SECONDARY
ECM FUSE
•NJP
PNK/BLK 439
BLK/RED 453
PPL/WHT 430
TAN/BLK 424
— WHT 423
-IGN
PRIMARY
WINDING
WHT 121
—I
DIRECT IGNITION
SYSTEM MODULE
TO I.P. OR v
TACH
f
W 1 6
— IGN
B16
B9
W19
W6
E C M
GROUND
REFERENCE
BY-PASS
EST
* 7 S 3 3 3 2 - 6 E
11-10-86
CHART C-4D-2
DIS" MISFIRE UNDERLOAD
2.5L "P" SERIES (TBI)
Circuit Description:
The "Direct Ignition System" (DIS) uses a waste spark method of distribution. In this type of 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 remainder of the high voltage to be used to fire #1 spark plug.
On this application, the crank sensor is mounted to the bottom of the coil/module assembly and protrudes through
the block to within approximately .050" of the crankshaft reluctor. Since the reluctor is a machined portion of the
crankshaft and the crank sensor is mounted in a fixed position on the block, timing adjustments are not possible
or necessary.
Test Description:
Numbers below refer to circled
numbers on the diagnostic chart.
1. If the "Misfire" complaint exists at idle only, the
diagnostic chart on page 1 must be used. 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 test gap on all 4 leads. This
simulates a "load" condition.
2. If the spark jumps the tester gap after grounding
the opposite plug wire, it indicates excessive
resistance in the plug which was bypassed. A
faulty or poor connection at that plug could also
result in the miss condition. Also check for carbon
deposits inside the spark plug boot.
3. If carbon tracing is evident replace coil and be sure
plug wires relating to that coil are clean and tight.
Excessive wire resistance or faulty connections
could have caused the coil to be damaged.
4. If the no spark condition follows the suspected coil,
that coil is faulty. Otherwise, the ignition module
is the cause of no spark. This test could also be
performed by substituting a known good coil for
the one causing the no spark condition.