Home ReviewsRefund
Home/Lexus/ES/Lexus ES V20 (1989-1991)/Repair manual/Testing & Diagnostics/Engine Controls - Tests W/o Codes
Contents Section: Testing & Diagnostics All sections

Engine Controls - Tests W/o Codes Lexus ES V20

Testing & Diagnostics ~2032 words

INTRODUCTION

Before diagnosing symptoms or intermittent faults, perform steps in BASIC TESTING and TESTS W/CODES articles. Use this article to diagnose driveability problems existing when a hard fault code is not present or vehicle is not equipped with a self-diagnostic system.

Note. Some driveability problems may have been corrected by manufacturer with a revised computer calibration chip or computer control unit. Check with manufacturer for latest chip or computer application.

Symptom checks can direct the technician to malfunctioning component(s) for further diagnosis. A symptom should lead to a specific component, system test or an adjustment.

Use intermittent test procedures to locate driveability problems that DO NOT occur when the vehicle is being tested. These test procedures should also be used if a soft (intermittent) trouble code was present, but no problem was found during self-diagnostic testing.

Note. For specific testing procedures, see SYSTEM/COMP TESTS article. For specifications, see ADJUSTMENTS or SPECIFICATIONS articles.

DIAGNOSIS BY SYMPTOM

When a diagnostic code cannot be confirmed or problem cannot be confirmed in BASIC TESTING , find basic symptom. For example, vehicle engine will not start. The appropriate heading matching vehicle symptom is DOES NOT START. Listed under DOES NOT START are more specific conditions. Find the specific condition which best fits your vehicle malfunction. Perform checks in order given. DO NOT skip sequence.

Note. Symptom diagnosis will refer to testing using a diagnostic code chart, even if a diagnostic code was not set.

ENGINE DOES NOT CRANK

  1. Check starter relay. See SYSTEM/COMP TESTS article.
  2. Check starter for proper operation.
  3. Check neutral start switch or clutch start switch. See SYSTEM/COMP TESTS article.
  4. Check theft deterrent ECU. See SYSTEM/COMP TESTS article.

STARTER RUNS, ENGINE DOES NOT CRANK

  1. Check starter for proper operation.
  2. Check flywheel or drive plate for damage.

NO INITIAL COMBUSTION

  1. Check distributor.
  2. Check ignition circuit. See CODE 14 in TESTS W/CODES article.
  3. Check EFI main relay. See SYSTEM/COMP TESTS article.
  4. Check circuit opening relay. See SYSTEM/COMP TESTS article.
  5. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  6. Check fuel pump. See SYSTEM/COMP TESTS article.
  7. Check fuel quality.
  8. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  9. Check engine compression, valve timing and timing belt.
  10. Check RPM signal circuit. See CODE 12 in TESTS W/CODES article.
  11. Check ECU. See SYSTEM/COMP TESTS article.

NO COMPLETE COMBUSTION

  1. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  2. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  3. Check fuel pump and fuel pressure regulator. See SYSTEM/COMP TESTS article.
  4. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  5. Check engine compression, piston rings, valve timing and timing belt.
  6. Check fuel injectors. See SYSTEM/COMP TESTS article.
  7. Check cold start system. See SYSTEM/COMP TESTS article.
  8. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE CRANKS SLOWLY

  1. Check starter for proper operation.
  2. Check A/C signal circuit. See CODE 51 in TESTS W/CODES article.
  3. Check connecting rod bearings and crankshaft bearings.

DIFFICULT TO START ORDINARILY

  1. Check fuel quality.
  2. Check spark plugs.
  3. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  4. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  5. Check EGR system. See SYSTEM/COMP TESTS article.
  6. Check fuel pump and fuel pressure regulator. See SYSTEM/COMP TESTS article.
  7. Check fuel lines for damage.
  8. Check RPM signal circuit. See CODE 12 in TESTS W/CODES article.
  9. Check ignition circuit. See CODE 14 in TESTS W/CODES article.
  10. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  11. Check distributor.
  12. Check fuel injectors. See SYSTEM/COMP TESTS article.
  13. Check cold start system. See SYSTEM/COMP TESTS article.
  14. Check ECU. See SYSTEM/COMP TESTS article.

DIFFICULT TO START WHEN COLD

  1. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  2. Check starter signal circuit. See CODE 43 in TESTS W/CODES article.
  3. Check fuel quality.
  4. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  5. Check cold start system. See SYSTEM/COMP TESTS article.
  6. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  7. Check fuel pump and fuel pressure regulator. See SYSTEM/COMP TESTS article.
  8. Check fuel lines for damage.
  9. Check fuel injectors. See SYSTEM/COMP TESTS article.
  10. Check ECU. See SYSTEM/COMP TESTS article.

DIFFICULT TO START WHEN HOT

  1. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  2. Check fuel quality.
  3. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  4. Check fuel pressure control system.
  5. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  6. Check cold start system. See SYSTEM/COMP TESTS article.
  7. Check fuel pump and fuel pressure regulator. See SYSTEM/COMP TESTS article.
  8. Check fuel lines for damage.
  9. Check fuel injectors. See SYSTEM/COMP TESTS article.
  10. Check ECU. See SYSTEM/COMP TESTS article.

INCORRECT FIRST IDLE

  1. Check accelerator pedal linkage.
  2. Check dashpot. See SYSTEM/COMP TESTS article.
  3. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  4. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  5. Check ECU. See SYSTEM/COMP TESTS article.

HIGH IDLE SPEED

  1. Check accelerator pedal linkage.
  2. Check dashpot. See SYSTEM/COMP TESTS article.
  3. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  4. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  5. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  6. Check throttle position sensor circuit. See CODE 41 in TESTS W/CODES article.
  7. Check A/C signal circuit. See CODE 51 in TESTS W/CODES article.
  8. Check switch condition signal. See CODE 51 in TESTS W/CODES article.
  9. Check fuel injectors. See SYSTEM/COMP TESTS article.
  10. Check cold start system. See SYSTEM/COMP TESTS article.
  11. Check ECU. See SYSTEM/COMP TESTS article.

LOW IDLE SPEED

  1. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  2. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  3. Check EGR system. See SYSTEM/COMP TESTS article.
  4. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  5. Check fuel injectors. See SYSTEM/COMP TESTS article.
  6. Check ECU. See SYSTEM/COMP TESTS article.

ROUGH IDLE

  1. Check fuel quality.
  2. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  3. Check EGR system. See SYSTEM/COMP TESTS article.
  4. Check spark plugs.
  5. Check distributor.
  6. Check fuel pump and fuel pressure regulator. See SYSTEM/COMP TESTS article.
  7. Check fuel lines for damage.
  8. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  9. Check engine compression and piston rings.
  10. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  11. Check valve clearance, valve timing and timing belt.
  12. Check fuel injectors. See SYSTEM/COMP TESTS article.
  13. Check cold start system. See SYSTEM/COMP TESTS article.
  14. Check ignition circuit. See CODE 14 in TESTS W/CODES article.
  15. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE MISFIRE

  1. Check fuel quality.
  2. Check EGR system. See SYSTEM/COMP TESTS article.
  3. Check spark plugs.
  4. Check ignition circuit. See CODE 14 in TESTS W/CODES article.
  5. Check distributor.
  6. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  7. Check engine compression.
  8. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  9. Check fuel injectors. See SYSTEM/COMP TESTS article.
  10. Check cold start system. See SYSTEM/COMP TESTS article.
  11. Check ECU. See SYSTEM/COMP TESTS article.

HESITATION, POOR ACCELERATION

  1. Ensure clutch operates properly.
  2. Ensure brakes do not drag.
  3. Check fuel quality.
  4. Check EGR system. See SYSTEM/COMP TESTS article.
  5. Check spark plugs.
  6. Check distributor.
  7. Check engine compression.
  8. Check throttle position sensor circuit. See CODE 41 in TESTS W/CODES article.
  9. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  10. Water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  11. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  12. Check main oxygen sensor circuit. See CODE 25 and CODE 26 in TESTS W/CODES article.
  13. Check fuel pump and fuel pressure regulator. See SYSTEM/COMP TESTS article.
  14. Check fuel lines for damage.
  15. Check valve clearance and valve timing.
  16. Check fuel injectors. See SYSTEM/COMP TESTS article.
  17. Check cold start system. See SYSTEM/COMP TESTS article.
  18. Check ECU. See SYSTEM/COMP TESTS article.

BACKFIRE

  1. Check EGR system.
  2. Check valve timing.
  3. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  4. Check throttle position sensor circuit. See CODE 41 in TESTS W/CODES article.
  5. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  6. Check main oxygen sensor circuit. See CODE 25 and CODE 26 in TESTS W/CODES article.
  7. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  8. Check fuel pump and fuel pressure regulator. See SYSTEM/COMP TESTS article.
  9. Check fuel lines for damage.
  10. Check fuel injectors. See SYSTEM/COMP TESTS article.
  11. Check ECU. See SYSTEM/COMP TESTS article.

MUFFLER EXPLOSION (AFTER FIRE)

  1. Check fuel cut system. See SYSTEM/COMP TESTS article.
  2. Check valve timing.
  3. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  4. Check fuel pump and fuel pressure regulator. See SYSTEM/COMP TESTS article.
  5. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  6. Check air intake temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  7. Check main oxygen sensor circuit. See CODE 25 and CODE 26 in TESTS W/CODES article.
  8. Check fuel injectors. See SYSTEM/COMP TESTS article.
  9. Check cold start system. See SYSTEM/COMP TESTS article.
  10. Check ECU. See SYSTEM/COMP TESTS article.

SURGING

  1. Check fuel pump and fuel pressure regulator. See SYSTEM/COMP TESTS article.
  2. Check spark plugs and distributor.
  3. Check fuel injectors. See SYSTEM/COMP TESTS article.
  4. Check ECU. See SYSTEM/COMP TESTS article.

KNOCKING

  1. Check knock sensing circuit. See Code 52 in TESTS W/CODES article.
  2. Check fuel quality.
  3. Check spark plugs.
  4. Check EGR system. See SYSTEM/COMP TESTS article.
  5. Check valve timing, radiator, radiator cap, thermostat and water pump.
  6. Check cooling fans. See SYSTEM/COMP TESTS article.
  7. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE STALL AFTER START

  1. Check fuel quality.
  2. Check fuel pump and fuel pressure regulator. See SYSTEM/COMP TESTS article.
  3. Check fuel lines for damage.
  4. Check EGR system. See SYSTEM/COMP TESTS article.
  5. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  6. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  7. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  8. Check fuel injectors. See SYSTEM/COMP TESTS article.
  9. Check cold start system. See SYSTEM/COMP TESTS article.
  10. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE STALL AFTER ACCELERATION PEDAL DEPRESSED

  1. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  2. Check EGR system. See SYSTEM/COMP TESTS article.
  3. Check throttle position sensor circuit. See CODE 41 in TESTS W/CODES article.
  4. Check spark plugs.
  5. Check fuel pump and fuel pressure regulator. See SYSTEM/COMP TESTS article.
  6. Check fuel lines for damage.
  7. Check fuel injectors. See SYSTEM/COMP TESTS article.
  8. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE STALL AFTER ACCELERATION PEDAL RELEASED

  1. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  2. Check EGR system. See SYSTEM/COMP TESTS article.
  3. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  4. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE STALL DURING A/C OPERATION

  1. Check A/C signal circuit. See CODE 51 in TESTS W/CODES article.
  2. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  3. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE STALL WHEN SHIFTING FROM NEUTRAL TO DRIVE

  1. Check neutral start switch signal. See CODE 51 in TESTS W/CODES article.
  2. Check idle speed control valve. See SYSTEM/COMP TESTS article.
  3. Check ECU. See SYSTEM/COMP TESTS article.

POOR FUEL ECONOMY

  1. Check for fuel leakage.
  2. Check fuel quality.
  3. Check accelerator linkage.
  4. Check dashpot. See SYSTEM/COMP TESTS article.
  5. Ensure clutch is operating properly.
  6. Ensure brakes do not drag when released.
  7. Check EGR system. See SYSTEM/COMP TESTS article.
  8. Check fuel cut system. See SYSTEM/COMP TESTS article.
  9. Check spark plugs and distributor.
  10. Check engine compression and valve timing.
  11. Check fuel injectors. See SYSTEM/COMP TESTS article.
  12. Check cold start system. See SYSTEM/COMP TESTS article.
  13. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  14. Check throttle position sensor circuit. See CODE 41 in TESTS W/CODES article.
  15. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article.
  16. Check neutral start switch signal. See CODE 51 in TESTS W/CODES article.
  17. Check A/C signal circuit. See CODE 51 in TESTS W/CODES article.
  18. Check main oxygen sensor signal circuit. See CODE 25 and CODE 26 in TESTS W/CODES article.
  19. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  20. Check sub-oxygen sensor circuit. See CODE 27 in TESTS W/CODES article.
  21. Check ECU. See SYSTEM/COMP TESTS article.

More articles — Engine Performance