SERVICE MANUAL NUMBER 23
FUEL INJECTION SYSTEM TROUBLESHOOTING
Page 5D-27
90-861326--1 MARCH 1999
Poor Fuel Economy Symptom
Step
Action
Value(s)
Yes
No
Definition: Fuel economy is noticeably lower than expected. Also, economy is noticeably
lower than it was on this engine at one time.
1
Was the “On-Board Diagnostic” (OBD)
System Check performed?
-
Go to Step 2
Go to OBD
System Check
2
Was visual/physical check performed?
-
Go to Step 3
Go to Visual/
Physical
Check
3
1. Check operators driving habits. Are
excessively heavy loads being car-
ried? Is operator accelerating too
much, too often?
2. If a problem is found, repair as nec-
essary.
Was a problem found?
-
System nor-
mal
Go to Step 4
4
1. Check flame arrestor for dirt or being
plugged.
2. Check for fuel leaks.
3. If a problem is found, repair as nec-
essary.
Was a problem found?
-
Go to OBD
System
Check
Go to Step 5
5
1. Check for proper fuel pressure.
•
Refer to Table A-4 in “General Sys-
tem Diagnostics” section.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
-
Go to OBD
System
Check
Go to Step 6
6
1. Check for proper operation of Igni-
tion Control (IC) circuit and the
Knock Sensor (KS) circuit.
2. If a problem is found, repair as nec-
essary.
Was a problem found?
-
Go to OBD
System
Check
Go to Step 7
7
1. Remove spark plugs, check for wet
plugs, cracks, wear, improper gap,
burned electrodes or heavy depos-
its.
•
Refer to Distributor Ignition System.
NOTE: 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 nec-
essary.
Was a problem found?
-
Go to OBD
System
Check
Go to Step 8
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