FUEL INJECTION SYSTEM TROUBLESHOOTING
SERVICE MANUAL NUMBER 24
Page 5F-24
90-861327--1 OCTOBER 1999
Backfire Symptom (Continued)
Step
Action
Yes
No
PROCEED TO
10
1. Check for proper ignition voltage input to
the ECM.
2. Check for intermittent open or short to
ground on the ignition voltage input circuit
to the ECM.
Was a problem found?
Step 11
11
1. Remove spark plugs, check for wet plugs,
cracks, wear, improper gap, burned elec-
trodes or heavy deposits.
•
Refer to Distributor Ignition System in
“Description and System Operation” sec-
tion.
NOTE: If park plugs are gas or oil fouled, the
cause of the fouling must be determined before
replacing the spark plugs
Were spark plugs damaged?
Step 12
12
1. Check for intermittent opens or short to
grounds in the MAP sensor and TP sensor
circuits. Also check for throttle linkage
sticking, binding or worn.
2. An intermittent failure may not store a DTC.
Was a problem found?
Step 13
13
1. Check engine mechanical for the following
conditions:
•
Low compression.
•
Sticking or leaking valves.
•
Worn camshaft lobe(s).
•
Incorrect valve timing.
Was a problem found?
Step 14
14
1. Check Intake and exhaust manifold(s) for
casting flash.
Was a problem found?
Step 15
15
1. Review all diagnostic procedures within
this table.
2. If all procedures have been completed and
no malfunctions have been found, review/
inspect the following:
•
Visual/physical inspection.
•
Scan tool data.
•
All electrical connections within a sus-
pected circuit and/or system.
Was a problem found?
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