Poor Fuel Economy Symptom - Isuzu C22NE Workshop Manual

Step
DEFINITION: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, economy
is noticeably lower than it was on this vehicle at one time, as previously shown by an actual road test.
Was the On-Board Diagnostic (OBD) System Check
1 performed?
1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found,
2
correct the condition as instructed in the bulletin.
Was a bulletin found that addresses the symptom?
Was a visual/physical check performed?
3
Check owner's driving habits.
• Is the A/C On full time (defroster mode ON)?
• Are tires at the correct pressure?
4
• Are excessively heavy loads being carried?
• Is acceleration too much, too often?
Review the items in Step 4 with the customer and advise
5 as necessary.
Is the action complete?
1. Visually/Physically check: Vacuum hoses for splits,
kinks, and improper connections and routing as shown
6
on the "Emission Control System schematics".
Was a problem found?
Remove and check the air filter element for dirt or for
7 restrictions.
Was a problem found?
1. Remove the spark plugs and check for gas or oil
fouling cracks, wear, improper gap, burned electrodes
of heavy deposits.
8
2. Is spark plugs are fouled, the cause of fouling must be
determined before replacing the spark plugs.
Was a problem found?
Check for low engine coolant level.
9
Was a problem found?
Check for an incorrect or faulty engine thermostat.
10 Refer to Engine Cooling.
Was a problem found?
Check for low engine compression. Refer to Engine
11 Mechanical.
Was a problem found?

Poor Fuel Economy Symptom

Action
DRIVEABILITY AND EMISSIONS 6E1-95
Value(s) Yes
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Go to Step 2
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Verify Repair
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Go to Step 4
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Go to Step 5
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System OK
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Verify repair
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Verify repair
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Verify repair
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Verify repair
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Verify repair
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Verify repair
No
Go to OBD
System
Check
Go to Step 3
Go to
Visual/Physic
al Check
Go to Step 6
-
Go to Step 7
Go to Step 8
Go to Step 9
Go to Step 10
Go to Step 11
Go to Step 12