Mercury MerCruiser MCM 454 Mag MPI Service Manual page 591

FUEL INJECTION SYSTEM TROUBLESHOOTING
Backfire Symptom (Continued)
12
13
14
15
Index
Page 5D-32
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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.
3. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check engine mechanical for the fol-
lowing conditions:
Low compression.
Sticking or leaking valves.
Worn camshaft lobe(s).
Incorrect valve timing.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check Intake and exhaust man-
ifold(s) for casting flash.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Review all diagnostic procedures
within this table.
2. If all procedures have been com-
pleted and no malfunctions have
been found, review/inspect the fol-
lowing:
Visual/physical inspection.
Scan tool data.
All electrical connections within a
suspected circuit and/or system.
3. If a problem is found, repair as nec-
essary.
Was a problem found?
SERVICE MANUAL NUMBER 23
Go to OBD
System
- Go to Step 13
Check
Go to OBD
System
- Go to Step 14
Check
Go to OBD
System
- Go to Step 15
Check
MerCruiser
Go to OBD
Customer
System
-
Check
90-861326--1 MARCH 1999
Contact
Service