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Diagnosis & Repair

  1. Check vacuum hoses for leaks, restrictions and proper routing. See VACUUM DIAGRAMS article for proper vacuum hose routing. Also, check engine wiring harness and electrical connectors for damage or poor connections. If no problems exist, go to next step. If problem exists, repair as necessary and perform TEST DRIVE CONFIRMATION .
  2. Remove spark plug for misfiring cylinder. Ensure no carbon deposits exist, spark plug is not fouled and spark plug gap is .039-.047" (1.00-1.20 mm). Check ignition system 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 system does not operate properly and spark does not exist, repair ignition system as necessary.
  3. Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. See Figure. Turn ignition on. Using voltmeter, check voltage between body ground and fuel injector driver terminal for misfiring cylinder at appropriate ECM electrical connector. See IDENTIFYING ECM FUEL INJECTOR DRIVER TERMINALS  table. For ECM electrical connector terminal identification, see Figure. If voltage is not 9-14 volts at fuel injector driver terminal, go to next step. If voltage is 9-14 volts at fuel injector driver terminal, go to step  6.
    IDENTIFYING ECM FUEL INJECTOR DRIVER TERMINALS

    Fuel Injector No. (1) ECM Electrical Connector & Terminal (2) Wire Color
    1 E4 Terminal No. 1 Black/Red
    2 E4 Terminal No. 2 Black
    3 E4 Terminal No. 3 White
    4 E4 Terminal No. 4 Red
    (1) Fuel injector No. 1 is at timing chain end of engine and fuel injector No. 4 is at flywheel end of engine.
    (2) For ECM electrical connector terminal identification, see Figure.
    Fig 1: Identifying Fuel Injector Signal Waveform Pattern & Fuel Injector Duration Signal Waveform Pattern
    G00032716Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  4. Disconnect electrical connector at fuel injector on misfiring cylinder. Using ohmmeter, check resistance between electrical terminals on fuel injector. Resistance should be 13.40-14.20 ohms at 68°F (20°C). If resistance is within specification, go to next step. If resistance is not within specification, replace fuel injector. See FUEL RAILS & FUEL INJECTORS under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
  5. Check for open and short in wiring harness and electrical connectors between fuel injector on misfiring cylinder and ECM. See WIRING DIAGRAMS article. If wiring harness or electrical connector is defective, repair as necessary. If wiring harness and electrical connectors are okay, it may be necessary to check for open and short in wiring harness and electrical connectors in fuel injector power supply circuit. See WIRING DIAGRAMS article.
  6. Check fuel pressure. See FUEL PRESSURE under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm2 ) with engine idling and should remain at least 21 psi (1.5 kg/cm2 ) for a minimum of 5 minutes after engine is shut off. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, repair fuel system as necessary.
  7. Check operation of fuel injector on misfiring cylinder. See FUEL CONTROL under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Fuel injector volume should be 53-65 cc (.18-.22 oz.) within 15 seconds and difference in volume between each fuel injector should be less than 6 cc (.02 oz.). Fuel injectors should not leak more than one drop every 12 minutes. If fuel injectors are okay, go to next step. If fuel injectors are defective, replace fuel injectors as necessary.
  8. Check Mass Airflow (MAF) meter and Engine Coolant Temperature (ECT) sensor. MAF meter may also be referred to as airflow meter. See AIRFLOW METER and ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If MAF meter and ECT sensor are okay, go to next step. If MAF meter or ECT sensor is defective, replace components as necessary. See AIRFLOW METER or ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
  9. Check engine compression on misfiring cylinder. See MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. Check valve clearance on misfiring cylinder. See VALVE CLEARANCE under ENGINE MECHANICAL in ON-VEHICLE ADJUSTMENTS - 4-CYLINDER article. Check valve timing. See appropriate article in ENGINES. Repair engine as necessary.
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