Service Manual — page 127 of 715

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FUEL SYSTEM (DFI) 3-37
DFI System Troubleshooting Guide

        Symptoms or Possible Causes                          Actions (chapter)
Subthrottle sensor trouble                    Inspect (see chapter 3).
Subthrottle valve actuator trouble            Inspect (see chapter 3).
Intake air pressure sensor #1 trouble         Inspect (see chapter 3).
Intake air pressure sensor #2 trouble         Inspect (see chapter 3).
Water temperature sensor trouble              Inspect (see chapter 3).
Intake air temperature sensor trouble         Inspect (see chapter 3).
Spark plug dirty, broken or gap maladjusted   Inspect and replace (see chapter 16).
Stick coil trouble                            Inspect (see chapter 16).
Stumble:
Fuel pressure too low                         Inspect (see chapter 3).
Fuel injector trouble                         Inspect (see chapter 3).
Main throttle sensor trouble                  Inspect (see chapter 3).
Subthrottle sensor trouble                    Inspect (see chapter 3).
Subthrottle valve actuator trouble            Inspect (see chapter 3).
Intake air pressure sensor #1 trouble         Inspect (see chapter 3).
Intake air pressure sensor #2 trouble         Inspect (see chapter 3).
Water temperature sensor trouble              Inspect (see chapter 3).
Intake air temperature sensor trouble         Inspect (see chapter 3).
Surge:
Unstable fuel pressure                        Fuel pressure regulator trouble (Inspect and
                                              replace fuel pump) or kinked fuel line (Inspect
                                              and replace fuel pump) (see chapter 3).
Fuel injector trouble                         Inspect (see chapter 3).
Water temperature sensor trouble              Inspect (see chapter 3).
Backfiring when deceleration:
Spark plug dirty, broken or gap maladjusted   Inspect and replace (see chapter 16).
Fuel pressure too low                         Inspect (see chapter 3).
Fuel pump trouble                             Inspect (see chapter 3).
Main throttle sensor trouble                  Inspect (see chapter 3).
Subthrottle sensor trouble                    Inspect (see chapter 3).
Subthrottle valve actuator trouble            Inspect (see chapter 3).
Intake air pressure sensor #1 trouble         Inspect (see chapter 3).
Intake air pressure sensor #2 trouble         Inspect (see chapter 3).
Water temperature sensor trouble              Inspect (see chapter 3).
Intake air temperature sensor trouble         Inspect (see chapter 3).
Air switching valve trouble                   Inspect and replace (see chapter 16).
Air suction valve trouble                     Inspect and replace (see chapter 5).
After fire:
Spark plug burned or gap maladjusted          Replace (see chapter 2).
Fuel injector trouble                         Inspect (see chapter 3).
Intake air pressure sensor #1 trouble         Inspect (see chapter 3).
Intake air pressure sensor #2 trouble         Inspect (see chapter 3).
Water temperature sensor trouble              Inspect (see chapter 3).
Intake air temperature sensor trouble         Inspect (see chapter 3).