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Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Toyota MR2. However, it is still accessible from the selected car via links, so may be relevant.
  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 for spark as misfiring cylinder by performing spark test. See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER 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 on driver's side of firewall behind driver's seat, luggage compartment lids and partition board. See Figure. Turn ignition on. Using DVOM, backprobe ECM connector and measure voltage between ground and fuel injector terminals at ECM harness connector E5. See IDENTIFYING ECM 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 ECM FUEL INJECTOR TERMINALS

    Fuel Injector No. (1) Terminal No. Wire Color
    1 1 Black/White
    2 2 Black
    3 3 Blue
    4 4 White
    (1) Terminals are located at 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 fuel injector on misfiring cylinder and ECM. 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 - 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 as specified, go to next step. If fuel pressure is not as specified, repair as necessary.
  7. Check operation of fuel injector on misfiring cylinder. See FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Fuel injector volume should be .16-.20 oz. (47-58 cc) every 15 seconds and difference in volume between each fuel injector should be less than .03 oz. (10 cc). Fuel injector should not leak more than one drop every 12 minutes. If problem does not exist, go to next step. If problem exists, repair as necessary.
  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 does not exist, go to next step. If problem exists, replace appropriate component.
  9. Check engine compression on misfiring cylinder. See BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Check valve clearance on misfiring cylinder. See ON-VEHICLE ADJUSTMENTS - 4-CYLINDER article. Check valve timing. See appropriate article in ENGINES. Repair as necessary.
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