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Diagnosis & Repair

  1. Check vacuum hoses for leaks, blockage and proper routing. See appropriate illustration in VACUUM DIAGRAMS article. Also, check wiring and connectors for damage or poor connections. If problem exists, repair as necessary and perform TEST DRIVE CONFIRMATION . If problem does not exist, go to next step.
  2. Check spark and ignition system. See IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  3. Access ECM behind bottom center of instrument panel, in front of console. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and fuel injector terminals at ECM harness connector E4. See IDENTIFYING FUEL INJECTOR TERMINALS  table. See Figure. If voltage is 9-14 volts at each terminal, go to step  6. If voltage is not 9-14 volts at each terminal, go to next step.
    IDENTIFYING FUEL INJECTOR TERMINALS

    Fuel Injector No. Terminal No. Wire Color
    1 12 Black/Red
    2 11 Black
    3 25 Black/Yellow
    4 24 Black/Blue
  4. Disconnect fuel injector harness connector at misfiring cylinder. Measure resistance between fuel injector terminals (component side). Resistance should be approximately 13.8 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace fuel injector.
  5. Check for open or short in wiring between ECM and fuel injector. See WIRING DIAGRAMS article. If problem exists, repair as necessary. If problem does not exist, repair open or short in injector power source circuit. See WIRING DIAGRAMS article.
  6. Check fuel pressure. See FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If fuel pressure is not within specification, repair as necessary. If fuel pressure is within specification, go to next step.
  7. Check fuel injectors. See FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  8. Check EGR system components. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  9. Check Manifold Absolute Pressure (MAP) sensor and Engine Coolant Temperature (ECT) sensor. See ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace appropriate component. If problem does not exist, go to next step.
  10. Check engine compression. See BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If engine compression is okay, check valve clearance. See ON-VEHICLE ADJUSTMENTS - 4-CYLINDER article. If valve clearance is okay, it may be necessary to check valve timing. See appropriate article in ENGINES.
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