Pontiac Fiero 1988 Service Manual page 554

DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI) 6E2-C4-7
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® IF ENGINE MSFIRES UNDER LOAD ONLY, SEE CHART C-4D-2.
• ENGINE IDLING AT NORMAL OPERATING TEMP., DISCONNECT I A C
• MOMENTARILY DISCONNECT EACH SPARK PLUG LEAD, USING
INSULATED PLIERS, WHILE OBSERVING ENGINE RPM. SEE C A U T I O N ^
• ALL PLUG LEAD(S) SHOULD RESULT IN AN RPM DROP. DID T H E Y ?
CHART C-4D-1
"DIS" MISFIRE AT IDLE
2.5L "P" SERIES (TBI)
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["NO"]
YES
• IGNTION OFF, INSTALL SPARK TESTER (ST-125) J-26792 OR EQUIVALENT
ON PLUG LEAD(S) WHICH DID NOT RESULT IN RPM DROP.
• SPARK SHOULD JUMP TESTER GAP WHILE CRANKING ENGINE. DOES IT?
I
SEE "ROUGH, UNSTABLE OR INCORRECT IDLE
OR STALLING" IN SYMPTOMS SECTION B.
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• IGNITION OFF, GROUND THE OPPOSITE PLUG
LEAD OF THE AFFECTED COIL AT SPARK PLUG.
• SPARK SHOULD JUMP TESTER GAP WHILE
CRANKING ENGINE. DOES IT?
• CHECK THE RESISTANCE OF EACH PLUG WIRE OF THE COIL
WHICH DID NOT FIRE THE SPARK TESTER.
• WIRE RESISTANCE SHOULD BE LESS THAN 30,000 OHMS EACH
AND WIRES SHOULD NOT BE GROUNDED. ARE WIRES OK?
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YES
HZ
• REMOVE COIL RETAINING NUTS AND REMOVE COILS.
COILS SHOULD BE FREE OF CARBON TRACKING. ARE T H E Y ?
YES
x :
• SWITCH A NORMALLY OPERATING COIL WITH THE
COIL FROM PROBLEM CYLINDER.
SPARK SHOULD JUMP TESTER GAP AT PROBLEM
CYLINDER WHILE CRANKING ENGINE. DID IT?
YES
ORIGINAL IGNITION
COIL IS FAULTY
YES
JL
CHECK FOR;
- FAULTY, WORN OR CRACKED SPARK PLUG(S)
- PLUG FOULING DUE TO ENGINE MECHANICAL FAULT.
IF SPARK PLUGS CHECK OUT OK, SEE "CUTS OUT,
MISSES" IN SYMPTOMS SECTION B.
YES
H Z
REPLACE THE SPARK PLUG FOR THE LEAD WHICH W A S
JUMPERED TO GROUND. IF MISFIRE IS STILL PRESENT,
START MISFIRE TEST AGAIN AT STEP #1.
NO
REPLACE
FAULTY WIRE(S)
NO
I
FAULTY IGNITION COIL. ALSO CHECK FOR
FAULTY PLUG WIRE CONNECTION(S) AND
WIRE NIPPLE(S) FOR CARBON TRACKING.
X
NO
FAULTY DIS
MODULE
^ C A U T I O N : W h e n h a n d l i n g secondary spark plug leads w i t h engine r u n n i n g ,
insulated pliers must be used and care exercised t o prevent a possible electrical shock.
CLEAR CODES AND CONFIRM " C L O S E D LOOP' OPERATION AND NO "SERVICE ENGINE S O O N " LIGHT.
6-10-86
7S 3573-6E