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Tests W/o Codes Mitsubishi Sigma pre-I

Testing & Diagnostics ~1598 words

INTRODUCTION

Use this section to diagnose driveability problems that exist when a hard fault code is not present or vehicle is not equipped with a self-diagnostic system. Symptom checks are intended to direct the technician to malfunctioning component(s) so that further diagnosis may be performed. A "symptom" should lead to further testing of specific components or systems, or verification of adjustment specifications.

Note. For specific component or system tests, see to

  1. Carbureted: «SYSTEM/COMPONENT TESTS - CARBURETED»(ref-18793)
  2. Fuel Injected: «SYSTEM/COMPONENT TESTS - EFI»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#systemcomponent-tests-efi)

For specifications, refer to

  1. Mitsubishi, see: «SPECIFICATIONS»(/mitsubishi/sigma/pre-i-1988-1989/remont/specifications/#specifications)

For adjustment procedures, refer to

  1. Mitsubishi, see: «ADJUSTMENTS»(/mitsubishi/sigma/pre-i-1988-1989/remont/adjustments/#adjustments) .

SYMPTOM DIAGNOSIS

Symptom checks cannot be used properly unless the problem is actually happening while the vehicle is being tested. To reduce diagnostic time, ensure steps in BASIC TESTING and TESTS W/CODES articles (if applicable) have been performed before attempting to diagnose a symptom. Refer to the following menu. For symptoms available for diagnosis see appropriate SYMPTOM-TO-DIAGNOSIS MENU under the appropriate Trouble Shooting (Carbureted), Trouble Shooting (PFI), or Trouble Shooting (TBI) Trouble Shooting heading below.

Basic Diagnosis

  1. Mitsubishi, see: «BASIC TESTING»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing)

Code Testing

  1. Mitsubishi, see: «TESTS W/CODES»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#tests-wcodes)

SYMPTOM-TO-DIAGNOSIS MENU (CARBURETED)

SymptomGo To
Difficult to startDIFFICULT TO START - CARBURETED
Rough or unstable idleROUGH/UNSTABLE IDLE - CARBURETED
Engine hesitates or missesHESITATES OR MISSES - CARBURETED
Poor fuel mileagePOOR FUEL MILEAGE - CARBURETED

SYMPTOM-TO-DIAGNOSIS MENU (CARBURETED)

DIFFICULT TO START - CARBURETED

  1. Ensure vacuum hoses are not disconnected or damaged.
  2. Ensure choke breaker operation and adjustment.
  3. Ensure electric choke operation and adjustment.
  4. Ensure needle valve not sticking or plugged.
  5. Ensure electrical harness, connectors and wires are not broken or loose.
  6. Check engine coolant temperature sensor operation.
  7. Check that ECU is mounted securely and functions properly.
  8. Check feedback solenoid operation.
  9. Check slow-cut solenoid valve operation.
  10. Check vacuum switch operation (cold engine).

ROUGH/UNSTABLE IDLE - CARBURETED

  1. Ensure dashpot operation and adjustment.
  2. Ensure electric choke operation and adjustment.
  3. Ensure fast idle operation (cold engine).
  4. Ensure proper idle adjustment (warm engine).
  5. Check primary pilot jet operation.
  6. Ensure vacuum hoses are not disconnected or damaged.
  7. Ensure electrical harness, connectors and wires are not broken or loose.
  8. Check engine coolant temperature sensor operation.
  9. Check engine speed sensor operation.
  10. Check slow-cut solenoid valve operation.
  11. Check throttle opener control system operation.
  12. Check throttle position sensor operation.

HESITATES OR MISSES - CARBURETED

  1. Check acceleration pump discharge rate.
  2. Check auxiliary acceleration pump discharge rate (cold engine).
  3. Check that enrichment jet passage is clear.
  4. Check enrichment valve operation.
  5. Check idle adjustment (warm engine).
  6. Check that main jet passage is clear.
  7. Check secondary valve operation.
  8. Ensure vacuum hoses are not disconnected or damaged.
  9. Ensure electrical harness, connectors and wires are not broken or loose.
  10. Check feedback solenoid operation.
  11. Check engine coolant temperature sensor operation.
  12. Check engine speed sensor operation.
  13. Check throttle position sensor operation.
  14. Check vacuum switch operation.

POOR FUEL MILEAGE - CARBURETED

  1. Ensure choke valve operation.
  2. Ensure electric choke operation.
  3. Check that enrichment valve is closed.
  4. Check that auxiliary acceleration pump is not operating (warm engine).
  5. Check feedback solenoid operation.
  6. Ensure electrical harness, connectors and wires are not broken or loose.
  7. Check engine coolant temperature sensor operation.
  8. Check engine speed sensor operation.
  9. Check Oxygen (O2) sensor operation.
  10. Check slow-cut solenoid valve operation.
  11. Check throttle position sensor operation.

SYMPTOM-TO-DIAGNOSIS MENU (PFI)

SymptomGo To
Difficult to startDIFFICULT TO START - PFI
Rough or unstable idleROUGH OR UNSTABLE IDLE - PFI
Engine hesitates or missesHESITATES OR MISSES - PFI
Poor fuel mileagePOOR FUEL MILEAGE - PFI

SYMPTOM-TO-DIAGNOSIS MENU (PFI)

DIFFICULT TO START - PFI

  1. Ensure vacuum hoses are not disconnected or damaged.
  2. Ensure electrical harness, connectors and wires are not broken or loose.
  3. Check voltage to ECU
  4. Check ECU operation.
  5. Check control relay operation.
  6. Ensure there are no codes in memory.
  7. Check fuel pump control system operation.
  8. Check that fuel pressure meets specification.
  9. Ensure ignition timing is correct.
  10. Check injector operation.
  11. Check power transistor operation.

ROUGH OR UNSTABLE IDLE - PFI

  1. Ensure vacuum hoses are not disconnected or damaged.
  2. Ensure electrical harness, connectors and wires are not broken or loose.
  3. Ensure there are no codes in memory.
  4. Check ECU operation.
  5. Check that fuel pressure meets specification.
  6. Check vehicle speed reed switch operation.
  7. Check injector operation.
  8. Check air conditioner switch operation.
  9. Check idle position switch operation.
  10. Check ignition switch operation.
  11. Check inhibitor switch operation (automatic transmission).
  12. Check power steering oil pressure switch operation.
  13. Check ISC Servo drive signal and operation.
  14. Check airflow sensor voltage output.
  15. Check barometric pressure sensor voltage output.
  16. Check crank angle sensor operation.
  17. Check engine coolant temperature sensor operation.
  18. Check intake air temperature sensor operation.
  19. Check motor position sensor operation.
  20. Check Oxygen (O2) sensor voltage output.
  21. Check throttle position sensor operation.
  22. Check TDC sensor or No. 1 cylinder TDC sensor (if equipped) operation.

HESITATES OR MISSES - PFI

  1. Ensure vacuum hoses are not disconnected or damaged.
  2. Ensure electrical harness, connectors and wires are not broken or loose.
  3. Ensure there are no codes in memory.
  4. Check air conditioner switch operation.
  5. Check air conditioner power relay operation.
  6. Check airflow sensor voltage output.
  7. Check barometric pressure sensor voltage output.
  8. Check crank angle sensor operation.
  9. Check engine coolant temperature sensor operation.
  10. Check that fuel pressure meets specification.
  11. Check idle position switch operation.
  12. Check ignition switch operation.
  13. Check inhibitor switch operation (automatic transmission).
  14. Check injector operation.
  15. Check intake air temperature sensor operation.
  16. Check ISC Servo drive signal and operation.
  17. Check motor position sensor operation.
  18. Check Oxygen (O2) sensor voltage output.
  19. Check power steering oil pressure switch operation.
  20. Check throttle position sensor operation.
  21. Check TDC sensor or No. 1 cylinder TDC sensor (if equipped) operation.

POOR FUEL MILEAGE - PFI

  1. Ensure there are no codes in memory.
  2. Check air conditioner switch operation.
  3. Check airflow sensor voltage output.
  4. Check barometric pressure sensor voltage output.
  5. Check engine coolant temperature sensor operation.
  6. Check that fuel pressure meets specification.
  7. Check idle position switch operation.
  8. Check ignition switch operation.
  9. Check inhibitor switch operation (automatic transmission).
  10. Check injector operation.
  11. Check intake air temperature sensor operation.
  12. Check motor position sensor operation.
  13. Check Oxygen (O2) sensor operation.
  14. Check power steering oil pressure switch operation.
  15. Check throttle position sensor operation.
  16. Check TDC sensor or No. 1 cylinder TDC sensor (if equipped) operation.

SYMPTOM-TO-DIAGNOSIS MENU (TBI)

SymptomGo To
Difficult to startDIFFICULT TO START - TBI
Rough or unstable idleROUGH OR UNSTABLE IDLE - TBI
Engine hesitates or missesHESITATES OR MISSES - TBI
Poor fuel mileagePOOR FUEL MILEAGE - TBI

SYMPTOM-TO-DIAGNOSIS MENU (TBI)

DIFFICULT TO START - TBI

  1. Ensure vacuum hoses are not disconnected or damaged.
  2. Ensure electrical harness, connectors and wires are not broken or loose.
  3. Check that ECU is mounted securely and is not visibly damaged.
  4. Check voltage to ECU
  5. Ensure there are no codes in memory.
  6. Check fuel pump control system operation.
  7. Check that fuel pressure meets specification.
  8. Check that ignition pulse is present.
  9. Check control relay operation.
  10. Check idle switch operation.
  11. Check injector operation.
  12. Check injector resistor operation.

ROUGH OR UNSTABLE IDLE - TBI

  1. Ensure vacuum hoses are not disconnected or damaged.
  2. Ensure electrical harness, connectors and wires are not broken or loose.
  3. Ensure there are no codes in memory.
  4. Check that fuel pressure meets specification.
  5. Check injector operation.
  6. Check injector resistor operation.
  7. Check air conditioner switch operation (idle up).
  8. Check idle switch operation.
  9. Check inhibitor switch operation.
  10. Check ISC Servo drive signal and operation.
  11. Check airflow sensor voltage output.
  12. Check barometric pressure sensor voltage output.
  13. Check engine coolant temperature sensor operation.
  14. Check engine speed sensor operation.
  15. Check intake air temperature sensor operation.
  16. Check motor position sensor operation.
  17. Check vehicle speed sensor operation.

HESITATES OR MISSES - TBI

  1. Ensure vacuum hoses are not disconnected or damaged.
  2. Ensure electrical harness, connectors and wires are not broken or loose.
  3. Ensure there are no codes in memory.
  4. Check that fuel pressure meets specification.
  5. Check injector operation.
  6. Check airflow sensor voltage output.
  7. Check barometric pressure sensor voltage output.
  8. Check engine coolant temperature sensor operation.
  9. Check engine speed sensor operation.
  10. Check intake air temperature sensor operation.
  11. Check throttle position sensor operation. Adjust or replace if necessary.

POOR FUEL MILEAGE - TBI

  1. Ensure there are no codes in memory.
  2. Check that fuel pressure meets specification.
  3. Check injector operation.
  4. Check Oxygen (O2) sensor operation.

INTERMITTENT PROBLEM DIAGNOSIS

Use this procedure to locate intermittent driveability problems that do not occur when the vehicle is being tested. These problems may cause a noticeable driveability problem or cause the "malfunction" warning light to illuminate on some vehicles. Before attempting to diagnose an intermittent fault, make sure procedures in the BASIC TESTING and TESTS W/CODES articles (if applicable) have been performed. Refer to the following menu. Intermittent fault testing requires you to duplicate a circuit or component failure, in order to identify the fault. These procedures may lead to the computer recording a fault code (on some systems) which may help in diagnosis.

  1. Mitsubishi, see: «BASIC TESTING»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#basic-testing)
  1. Mitsubishi, see: «TESTS W/CODES»(/mitsubishi/sigma/pre-i-1988-1989/remont/testing-diagnostics/#tests-wcodes)

If problem vehicle does not produce fault codes, it will be necessary to monitor voltage or resistance values using a DVOM while attempting to produce conditions which will create an intermittent fault. A change in status on the DVOM will indicate a fault has been located.

Intermittent Simulation

To produce the conditions which create an intermittent fault so that it may be identified during testing, some of the following methods may be used

  1. Applying light vibration to components.
  2. Heating a component.
  3. Wiggling or bending a wiring harness.
  4. Applying humidity to a component.
  5. Remove or apply a vacuum supply source.

Monitor component voltage, or monitor for self-diagnostic codes while attempting to simulate intermittent. Use the results of these tests to identify a faulty component or an area which should be checked closely for the problem.

Note. Intermittent problems are often caused by poor harness connector. It is important to check harness connector contact.

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