Mercury MERCRUISER, Service Manual, Page: 84 / 566

Step Action Yes No
15
Using an engine cleaner, remove excessive carbon buildup
from the combustion chambers.
NOTE: Refer to the instructions on the engine cleaner.
Retest the system.
Is detonation still present?
Go to step 16. Done.
16
Review all of the procedures in this table. If all procedures have been completed and no problem found, inspect the
following:
• CDS G3 scan tool data
NOTE: If there is an active fault
Engine_Misfire
, refer to the
PCM 112 Service Manual
or to
MerCruiser Service Bulletin
2011
‑
11R2
.
• All of the electrical connections within a suspect circuit or system
Chart S4: Hesitation, Sag, or Stumble
Definition: Momentary lack of response as the throttle lever is advanced. Can occur at all engine speeds, but usually more
severe when first starting out. May cause engine to stall in severe cases.
Step Action Yes No
1 Was the
Visual/Physical Check
completed? Go to step 2.
Go to the
Visual/
Physical Check
.
2 Did the onboard diagnostic (OBD) system check complete? Go to step 3.
Connect the CDS G3
service tool and scan for
faults.
3
Inspect the flame arrestor for restrictions, dirt, or damage.
Was a problem found?
Clean or replace the flame
arrestor.
Retest system.
Go to step 4.
4
Check for intermittent opens or shorts to ground in the MAP
sensor circuit.
Was a problem found?
Locate and repair the problem
in the harness.
Retest system.
Go to step 5.
5
• Using the scan tool, check for proper operation of the
TPS.
• Check throttle linkage for sticking, binding, or wear.
Was a problem found?
Locate and repair the problem
with the TPS or the throttle
linkage.
Retest system.
Go to step 6.
6
• Check for contaminated fuel.
• Check fuel filters and the water‑separating fuel filter.
• Check for poor fuel quality and improper octane rating.
Was a problem found?
Use known good fuel.
Replace fuel filters.
Go to step 7.
7
Check for proper fuel pressure while the condition exists.
Was a problem found?
Go to
Chart T3
. Go to step 8.
8
Check the fuel injectors.
Was a problem found?
Repair or replace the faulty
injector.
Go to step 9.
9
Remove the spark plugs and check them for moisture, cracks,
wear, improper gap, burned electrodes, or heavy deposits.
NOTE: If the spark plugs are fouled with gas or oil, determine
the cause of the fouling before replacing the spark plugs.
Was a problem found?
Replace the spark plugs. Go to step 10.
10 Check the alternator voltage output.
Is the output 13.9–14.7 V?
Go to step 11.
Refer to
Section 4C
‑
Charging System
.
11
Check for obvious overheating issues:
• Loose serpentine belt
• Faulty or incorrect seawater pump
• Restriction in the cooling system
• Faulty or incorrect thermostat
Was a problem found?
Repair or replace.
Retest system.
Go to step 12.
Troubleshooting
Page 1D-14 © 2016 Mercury Marine 90-8M0099748 eng DECEMBER 2015