Hesitation, Sag, Stumble Symptom - Mercury MerCruiser MCM 454 Mag MPI Service Manual

SERVICE MANUAL NUMBER 23

Hesitation, Sag, Stumble Symptom

Step
Definition: Momentary lack of response as the throttle lever is advanced. Can occur at
all engine speeds. Usually most severe when first starting out. May cause engine to stall
if severe enough.
Index
90-861326--1 MARCH 1999
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Action
Was the "On-Board Diagnostic" (OBD)
1
System Check performed?
Was visual/physical check performed?
2
1. Check for contaminated fuel.
2. Check water separating fuel filter.
3
3. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check or proper fuel pressure while
the condition exists.
Refer to Table A-4 in "General Sys-
4 tem Diagnostics" section.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check fuel injectors.
Refer to Injector Balance Test in
"Test General System Diagnostics"
5
section.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check for proper operation of Igni-
tion Control (IC) circuit and the
Knock Sensor (KS) circuit.
6
2. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check integrity of the primary and
secondary wiring.
2. Check routing of the wiring.
3. Check condition of IC module,
7
pick-up coil, distributor cap, rotor
and spark plug wires.
4. If a problem is found, repair as nec-
essary.
Was a problem found?
FUEL INJECTION SYSTEM TROUBLESHOOTING
Value(s) Yes
Go to Step 2
-
- Go to Step 3
Go to OBD
System
-
Check
Go to OBD
System
-
Check
Go to OBD
System
-
Check
Go to OBD
System
-
Check
Go to OBD
System
-
Check
No
Go to OBD
System Check
Go to Visual/
Physical
Check
Go to Step 4
Go to Step 5
Go to Step 6
Go to Step 7
Go to Step 8
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