Service Manual — page 126 of 715

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3-36 FUEL SYSTEM (DFI)
DFI System Troubleshooting Guide

       Symptoms or Possible Causes                            Actions (chapter)
Fuel pressure regulator trouble               Inspect fuel pressure and replace fuel pump (see
                                              chapter 3).
Fuel line clogged                             Inspect and repair (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).
Main throttle sensor trouble                  Inspect (see chapter 3).
Subthrottle sensor trouble                    Inspect (see chapter 3).
Subthrottle valve actuator trouble            Inspect (see chapter 3).
Unstable (rough) idling:
Fuel pressure too low or too high             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).
Engine vacuum not synchronizing               Inspect and adjust (see chapter 2).
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).
Engine stalls easily:
Spark plug dirty, broken or gap maladjusted   Inspect and replace (see chapter 16).
Stick coil trouble                            Inspect (see chapter 16).
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).
Fuel pump trouble                             Inspect (see chapter 3).
Fuel injector trouble                         Inspect (see chapter 3).
Fuel pressure too low or too high             Inspect (see chapter 3).
Fuel pressure regulator trouble               Inspect fuel pressure and replace fuel pump (see
                                              chapter 3).
Fuel line clogged                             Inspect and repair (see chapter 3).
Poor acceleration:
Fuel pressure too low                         Inspect (see chapter 3).
Water or foreign matter in fuel               Change fuel. Inspect and clean fuel system (see
                                              chapter 3).
Fuel filter or pump screen clogged            Inspect and replace fuel pump (see chapter 3).
Fuel pump trouble                             Inspect (see chapter 3).
Fuel injector trouble                         Inspect (see chapter 3).
Main throttle sensor trouble                  Inspect (see chapter 3).