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Engine Controls - Trouble Shooting - No Codes: Other Kia Optima I

Testing & Diagnostics ~1188 words

CRANKS NORMALLY BUT WILL NOT START

  1. Check for spark.
  2. Check for fuel pump operation.
  3. Check fuel system pressure.
  4. Check fuel injector operation.
  5. Check engine compression.
  6. Check Crankcase Position (CKP) sensor.
  7. Check voltages of Mass Airflow (MAF) sensor, Throttle Position (TP) sensor, ignition coils and Engine Coolant Temperature (ECT) sensor at Engine Control Module (ECM).
  8. Check for contaminated MAF sensor.
  9. Check for intake air leak.
  10. Check spark plug condition.
  11. Check Engine Control Module (ECM) power and grounds.
  12. If no start after engine is warmed up, disconnect ECT and check if engine starts.

CRANKS NORMALLY BUT DIFFICULT TO START

  1. Check for strong spark.
  2. Check Engine Control Module (ECM) ground and power circuits.
  3. Check intake manifold vacuum. Vacuum should be more than 18.9 in. Hg (1.8L), or 17.7 in. Hg (2.0L), at idle.
  4. Check air filter element.
  5. Check if engine starts with throttle 1/4 open. If engine starts, check for carbon deposit on throttle valve.
  6. Check that engine starts while fuel pump is running.
  7. Check fuel pressure while engine is idling.
  8. Check for fuel injector operation while cranking engine.
  9. Check fuel system holding pressure.
  10. Check terminal voltages of Mass Airflow (MAF) sensor, Throttle Position (TP) sensor, ignition coils and Engine Coolant Temperature (ECT) sensor at Engine Control Module (ECM).
  11. Check for contaminated MAF sensor element.
  12. Check spark plug condition.
  13. Check Idle Air Control (IAC) valve.
  14. Check if engine starts with ECT disconnected.

ROUGH OR UNSTABLE IDLE

  1. Check terminal voltages of Mass Airflow (MAF) sensor, Throttle Position (TP) sensor, ignition coils and Engine Coolant Temperature (ECT) sensor at Engine Control Module (ECM).
  2. Use stethoscope to verify fuel injector operating noise.
  3. Check for battery voltage to injectors when ignition is on.
  4. Check resistance of injectors.
  5. Check TP sensor.
  6. Check for contaminated MAF sensor element.
  7. Check engine compression.
  8. Check air filter element.
  9. Check for air intake system leaks.
  10. Check intake manifold vacuum. Vacuum should be more than 18.9 in. Hg (1.8L), or 17.7 in. Hg (2.0L), at idle.
  11. Disconnect ECT sensor and check if engine condition improves.
  12. Check ECT sensor resistances.
  13. Check EGR system, check EGR valve stuck open and EGR solenoid for proper operation.
  14. Disconnect Oxygen sensor and check if engine condition improves.
  15. Check fuel pressure.
  16. If A/C is on, turn off A/C and observe if condition improves.

HIGH IDLE AFTER WARM-UP

  1. Check that throttle valve closes completely when accelerator pedal is released.
  2. Check throttle cable adjustment.
  3. Check PCV valve operation.
  4. Disconnect Engine Coolant Temperature (ECT) sensor and see if engine idle improves.
  5. Check ECT sensor resistances.
  6. Check Throttle Position (TP) sensor.
  7. Ensure Engine Control Module (ECM) terminal voltages are okay.
  8. Check for vacuum leaks.

ENGINE STALLS ON DECELERATION

  1. Check idle condition. If vehicle does not idle properly, see «ROUGH OR UNSTABLE IDLE»(ref-12020-S21755231382000120400000) .
  2. Check Throttle Position (TP) sensor.
  3. Check Idle Air Control (IAC) valve.
  4. Ensure Engine Control Module (ECM) terminal voltages are okay.
  5. Check EGR system, check EGR valve for sticking open and EGR solenoid for proper operation.
  6. Disconnect Oxygen sensor and check if engine condition improves.
  7. Check for poor connections at ignition coil, ignitor, distributor, high tension leads, TP sensor, Mass Airflow (MAF) sensor, Crankshaft Position (CKP) sensor, Camshaft Position (CMP) sensor, injectors, fuel pump relay and ECM.

ENGINE STALLS INTERMITTENTLY

  1. Check idle condition. If vehicle does not idle properly, see «ROUGH OR UNSTABLE IDLE»(ref-12020-S21755231382000120400000) .
  2. Ensure Engine Control Module (ECM) terminal voltages are okay.
  3. Check for poor connections at ignition coils, Throttle Position (TP) sensor, Mass Airflow (MAF) sensor, Crankshaft Position (CKP) sensor, fuel injector, fuel pump relay and ECM.
  4. Check that MAF sensor and CKP sensor output signals are normal.
  5. Check EGR system, check EGR valve for sticking open and EGR solenoid for proper operation.
  6. Disconnect Oxygen sensor and check if engine condition improves.
  7. Perform «INTERMITTENT PROBLEM DIAGNOSIS»(ref-12020-S20311513832000120400000) under INTERMITTENTS.

ENGINE HESITATES OR STUMBLES ON ACCELERATION

  1. Check intake manifold vacuum. Vacuum should be more than 18.9 in. Hg (1.8L), or 17.7 in. Hg (2.0L), at idle.
  2. Check air filter element.
  3. Check Mass Airflow (MAF) sensor.
  4. Check MAF sensor element for contamination.
  5. Check Engine Coolant Temperature (ECT) sensor.
  6. Check Throttle Position (TP) sensor.
  7. Disconnect injectors in turn and check for equal RPM drop between cylinders.
  8. Check throttle linkage operation.
  9. Check fuel pressure.
  10. Check air passage and vacuum hose installation.
  11. Check for restricted exhaust system.

ENGINE SURGES WHILE CRUISING

  1. Check intake manifold vacuum. Vacuum should be more than 18.9 in. Hg (1.8L), or 17.7 in. Hg (2.0L), at idle.
  2. Check Throttle Position (TP) sensor.
  3. Check oxygen sensor.
  4. Check for normal Vehicle Speed Sensor (VSS) signal to Engine Control Module (ECM).
  5. Ensure Engine Control Module (ECM) terminal voltages are okay.
  6. Check throttle linkage operation.
  7. Check air filter element.
  8. Check fuel system pressure.
  9. Check for restricted exhaust system.

LACK OF POWER

  1. On M/T models, ensure clutch is not slipping.
  2. On A/T models, ensure transmission is not slipping.
  3. Ensure brakes do not drag.
  4. Ensure tire size and air pressure are to specification.
  5. Check throttle linkage installation and operation.
  6. Check operation of throttle body.
  7. Check Camshaft Position (CMP) sensor.
  8. Check Throttle Position (TP) sensor.
  9. Check intake manifold vacuum. Vacuum should be more than 18.9 in. Hg (1.8L), or 17.7 in. Hg (2.0L), at idle.
  10. Disconnect injectors in turn and check for equal RPM drop between cylinders.
  11. Check air filter element.
  12. Check fuel system holding pressure.
  13. Check that fuel pressure increases when abruptly accelerating.
  14. Check Mass Airflow (MAF) sensor.
  15. Check MAF sensor element for contamination.
  16. Check spark plug condition.
  17. Check spark plug wires.
  18. Check ignition coil resistance.
  19. Check engine compression.
  20. Check for restricted exhaust system.
  21. Check fuel filter.
  22. Check for contaminated fuel.

ENGINE RUNS ROUGH ON DECELERATION

  1. Check intake manifold vacuum. Vacuum should be more than 18.9 in. Hg (1.8L), or 17.7 in. Hg (2.0L), at idle.
  2. Check air filter element.
  3. Ensure Engine Control Module (ECM) terminal voltages are okay.
  4. Check fuel injection system.
  5. Check Mass Airflow (MAF) sensor.
  6. Check MAF sensor element for contamination.
  7. Check Throttle Position (TP) sensor.
  8. Check throttle body for contamination.
  9. Check for leaking fuel injectors.
  10. Check EGR system, check EGR valve for sticking open and EGR solenoid for proper operation.

FUEL ODOR

  1. Check fuel evaporative control system.
  2. Check fuel system for leaks or damage.

EXCESSIVE OIL CONSUMPTION

  1. Check for restricted PCV system.
  2. Check for leaks.
  3. Check for worn engine parts.
  4. Check for fuel dilution of oil.

POOR FUEL MILEAGE

  1. On M/T models, ensure clutch is not slipping.
  2. On A/T models, ensure transmission is not slipping.
  3. Ensure brakes do not drag.
  4. Ensure tire size and air pressure are to specification.
  5. Check alignment.
  6. Check for restricted exhaust system.
  7. Ensure all vacuum hoses are connected correctly.
  8. Check intake manifold vacuum. Vacuum should be more than 17.7 in. Hg at idle.
  9. Check air filter element.
  10. Check spark plugs.
  11. Check compression.
  12. Ensure Engine Control Module (ECM) terminal voltages are okay.
  13. Ensure fuel system pressure is correct.

Intermittent Simulation

To reproduce conditions creating an intermittent fault, use the following methods

  1. Lightly vibrate component.
  2. Heat component.
  3. Wiggle or bend wiring harness.
  4. Spray component with water.
  5. Remove/apply vacuum source.

Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for Diagnostic Trouble Codes (DTCs) or pending codes. Use test results to identify a faulty component or circuit.

More articles — Engine Controls - Trouble Shooting - No Codes