PleasureCraft Engine Group 5.0L, Diagnostic Manual

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5.0/5.7/6.0L/8.1L Symptoms 7 - 19
MEFI 4 - PCM
Poor Fuel Economy Symptom
Step Action Value Yes No
Defi nition: Fuel economy, as measured at selected intervals, is noticeably lower than expected. Also, economy
is noticeably lower than it was on this vehicle at one time, as previously shown by documentation.
1
Was the “On-Board Diagnostic (OBD) System Check” Go to OBD
performed? — Go to Step 2 System Check
2
Was visual/physical check performed? Go to Visual/
— Go to Step 3 Physical check
1. Check owner’s driving habits.
Are excessively heavy loads being carried?
3
Is accelerating too much, too often?
2. If a problem is found, repair as necessary.
Was a problem found? — System normal
Go to Step 4
1. Check for correct base ignition timing.
4
•
Refer to “Ignition Timing Set Procedure” in the
Distributor Ignition section.
2. If a problem is found, repair as necessary. Go to OBD
Was a problem found? — System Check Go to Step 5
1. Check fl ame arrestor for dirt or being plugged.
5
2. Check for fuel leaks.
3. If a problem is found, repair as necessary. Go to OBD
Was a problem found? — System Check Go to Step 6
1. Check for proper fuel pressure.
6
•
Refer to Table A-4.
2. If a problem is found, repair as necessary. Go to OBD
Was a problem found? — System Check Go to Step 7
1. Check for proper operation of Ignition Control (IC)
7
circuit and the Knock Sensor (KS) circuit(s).
2. If a problem is found, repair as necessary. Go to OBD
Was a problem found? — System Check Go to Step 8
1. Remove spark plugs, check for wet plugs, cracks, wear,
improper gap, burned electrodes or heavy deposits.
•
Refer to Table A-6
8
Notice: If spark plugs are gas or oil fouled, the cause of
the fouling must be determined before replacing the
spark plugs.
2. If a problem is found, repair as necessary. Go to OBD
Was a problem found? — System Check Go to Step 9
1. Visually (physically) check vacuum hoses for splits,
9
kinks and improper connections and routing.
2. If a problem is found, repair as necessary. Go to OBD
Was a repair required? — System Check Go to Step 10
1. Check engine compression for being low.
10
2. If a problem is found, repair as necessary. Go to OBD
Was a problem found? — System Check Go to Step 11