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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 below stereo, behind instrument panel, just in front of center console. See Figure. Turn ignition on. Using DVOM, backprobe ECM connector and measure voltage between ground and fuel injector terminals at appropriate ECM harness connector. See IDENTIFYING FUEL INJECTOR TERMINALS  table. See Figure or 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
    With 4A/T Transmission (1)
    1 1 Yellow
    2 2 Black/Red
    3 3 White
    4 4 Black
    Without 4A/T Transmission (2)
    1 12 Yellow
    2 11 Black/Red
    3 25 White
    4 24 Black
    (1) Terminals are located at ECM harness connector E7. See Figure.
    (2) Terminals are located at ECM harness connector E4. See Figure.
  4. Disconnect fuel injector harness connector at misfiring cylinder. Measure resistance between fuel injector terminals (component side). Resistance should be 13.4-14.2 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. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm2 ) at idle, and should be 21 psi (1.5 kg/cm2 ) or more for 5 minutes after engine has stopped. If fuel pressure is not as specified, repair as necessary. If fuel pressure is as specified, go to next step.
  7. Check fuel injectors. See FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Fuel injector volume should be 3.7-4.5 cu. in. (60-73 cc) every 15 seconds and difference in volume between each injector should be less than .8 cu. in. (13 cc). Injectors should not leak more than one drop every 12 minutes. If problem exists, repair as necessary. If problem does not exist, go to next step.
  8. Check Mass Airflow (MAF) meter 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.
  9. Check engine compression. See BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Check valve clearance. See ON-VEHICLE ADJUSTMENTS - 4-CYLINDER article. Check valve timing. See appropriate article in ENGINES. Repair as necessary.
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