Mercury MerCruiser MCM 454 Mag MPI Service Manual page 579

FUEL INJECTION SYSTEM TROUBLESHOOTING
Hesitation, Sag, Stumble Symptom (Continued)
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9
10
11
12
13
Index
Page 5D-20
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1. Remove spark plugs and check for
wet plugs, cracks. wear, improper
gap, burned electrodes or heavy
deposits.
Refer to Distributor Ignition System.
NOTE: If park plugs are gas or oil fouled,
the cause of the fouling must be deter-
mined before replacing the spark plugs.
2. If a problem is found, repair as nec-
essary
Was a problem found?
1. Check for the ECT sensor shifted in
value.
2. Check for intermittent opens or short
to grounds in the ECT sensor, MAP
sensor and TP sensor circuits. Also
check or throttle linkage sticking,
binding or worn.
3. An intermittent failure may not store
a DTC.
4. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check for engine going into rpm
reduction mode.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check for proper alternator voltage
output.
2. The voltage should be between spe-
cified values.
3. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check for faulty or incorrect thermo-
stat.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
1. Check intake valves for valve
deposits.
2. If deposits are found, remove as
necessary.
Were deposits found on the intake
valves?
SERVICE MANUAL NUMBER 23
Go to OBD
System
-
Check
Go to OBD
System
-
Check
Not
Applicable
to MerCruis-
er
-
EFI or MPI
Go to OBD
11-16
System
Volts
Check
Go to OBD
System
-
Check
Go to OBD
System
-
Check
90-861326--1 MARCH 1999
Go to Step 9
Go to Step 10
Go to Step 11
Go to Step 12
Go to Step 13
Go to Step 14