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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 does not exist, go to next step. If problem exists, repair as necessary and perform TEST DRIVE CONFIRMATION .
  2. Check ignition system by performing spark test. See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. If ignition system operates properly and spark exist, go to next step. If ignition does not operate properly and spark does not exist, repair ignition system as necessary.
  3. Access ECM behind glove box. See Figure. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and fuel injector terminals at specified ECM harness connector. See IDENTIFYING FUEL INJECTOR TERMINALS  table. See Figure. If voltage is not 9-14 volts at each terminal, go to next step. If voltage is 9-14 volts at each terminal, go to step  6.
    IDENTIFYING FUEL INJECTOR TERMINALS

    Fuel Injector No. Terminal No. Wire Color
    1 5 (1) Yellow
    2 6 (1) Black
    3 1 (2) Blue
    4 2 (2) Red
    5 3 (2) Green
    6 4 (2) Red/Blue
    7 5 (2) White
    8 6 (2) Black/White
    (1) Terminal are located in ECM harness connector E6. See Figure.
    (2) Terminals are located in ECM harness connector E5. 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 fuel injector power source circuit. See WIRING DIAGRAMS article.
  6. Check fuel pressure. See FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Fuel pressure should be 38-44 psi (2.7-3.1 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 as specified, go to next step. If fuel pressure is not as specified, repair as necessary.
  7. Check opeation of fuel injector on misfiring cylinder. See FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. Fuel injector volume should be 3.4-4.2 Cu. In. (56-69 cc) every 15 seconds and difference in volume between each fuel injector should be less than .8 Cu. In. (13 cc). Fuel 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 - V6 & V8 article. If problem exists, replace appropriate component. If problem does not exist, go to next step.
  9. Check engine compression on misfiring cylinder. See BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Check valve clearance on misfiring cylinder. See ON-VEHICLE ADJUSTMENTS - V6 & V8 article. Check valve timing. See appropriate article in ENGINES. Repair as necessary.
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