SFI SYSTEM Rough Idling

DESCRIPTION

Problem Symptom Suspected Area Trouble Area

  • Engine speed fluctuation due to abnormal combustion

  • Idle speed too low or high

Strong engine vibration due to above symptoms


  • Ignition malfunction

  • Deviation in air fuel ratio (Excessive or insufficient intake air volume or fuel supply)

  • Insufficient compression

  • Changes in load from another system

Ignition system
  • Spark plug

  • Ignition coil assembly

Fuel system
  • Fuel injector assembly

  • Fuel pump

  • Fuel pump control circuit

  • Fuel line

  • Purge VSV system

  • Fuel quality (existence of foreign matter, degradation)

Intake and exhaust systems
  • Mass air flow meter sub-assembly

  • Intake system

    (Air leaks or deposit accumulation)

  • Throttle body with motor assembly

  • Air fuel ratio sensor

  • Heated oxygen sensor

  • Camshaft timing oil control assembly

  • Variable Valve Timing system (VVT system)

  • Brake booster assembly

Other control systems
  • ECM

  • Wire harness or connector

  • Knock control sensor

  • Engine coolant temperature sensor

Engine
  • Thermostat

  • Engine assembly

High load from another system
  • Air conditioning system

  • Power steering system

  • Electrical load signal system

Tech Tips


  • If any other DTCs are output, perform troubleshooting for those DTCs first.

  • Make sure to reproduce the conditions present when the malfunction occurred.

  • Using the GTS, read the Data List to confirm the engine operating conditions. This information can be useful when troubleshooting.

  • If the problem symptoms do not recur, attempt to reproduce the symptoms and conditions when the malfunction occurred based on the result of the customer problem analysis. Place the priority on confirming the symptoms.


  1. SYMPTOM AND CAUSE OF SYSTEM MALFUNCTION

    Tech Tips

    The following are descriptions of the characteristics of each system malfunction. After understanding the link between the causes and symptoms, perform the inspection of each component. Even if the problem symptom does not recur, signs of the malfunction may be found in the Data List.


    1. Ignition system

      Spark plug
      Main cause of malfunction Performance degradation (wear, existence of foreign matter, etc.)
      Symptom Engine speed fluctuation due to abnormal combustion

      Tech Tips

      If the spark plug of the malfunctioning cylinder is abnormally wet with fuel, a leaking fuel injector assembly is suspected.

      Ignition coil assembly
      Main cause of malfunction Internal malfunction
      Problem symptom Engine speed fluctuation due to abnormal combustion
    2. Fuel system

      Fuel injector assembly
      Main cause of malfunction Blockage
      Problem symptom
      • Engine speed fluctuation due to abnormal combustion

      • Idle speed too low or high

      Data List
      • Short FT

      • Long FT

      • Fuel System Status

      • Target Air-Fuel Ratio

      • AF Lambda

      • A/F Learn Value Idle

      • A/F Learn Value Low

      • A/F Learn Value Mid1

      • A/F Learn Value Mid2

      • A/F Learn Value High

      Tech Tips

      If the engine malfunction disappears when the fuel injection volume is increased or decreased using the Control the Injection Volume, the respective cylinder may be malfunctioning.

      Fuel system

      Tech Tips

      If the air fuel ratio becomes lean only when the engine is running under a high load and at a high engine speed, clogging of the fuel pump or fuel filter is suspected.

      Fuel quality
      Main cause of malfunction
      • Fuel degradation due to age or water contamination

      • Low fuel quality

      • Addition of fuel additive

      Problem symptom
      • Engine speed fluctuation due to abnormal combustion

      • Idle speed too low or high

      • Engine is difficult to start

    3. Intake and exhaust systems

      Mass air flow meter sub-assembly
      Main cause of malfunction Performance degradation (existence of foreign matter, etc.)
      Problem symptom Lack of power
      Data List MAF

      Tech Tips

      If the value of the Data List item "MAF" is abnormal, a malfunction of the mass air flow meter sub-assembly is suspected.

      Throttle system
      Main cause of malfunction Inappropriate trim volume adjustment due to accumulation of deposits
      Problem symptom
      • Engine speed fluctuation due to abnormal combustion

      • Idle speed too low or high

      Data List
      • ISC Learning Value

      • ISC Flow

      • ISC Feedback Value

      • Electric Load Feedback Val

      • Air Conditioner FB Val

      • Eng Stall Control FB Flow

      Air fuel ratio sensor, Heated oxygen sensor
      Main cause of malfunction Deviation in sensor characteristics
      Problem symptom Abnormal combustion due to deviation of actual air fuel ratio from calculated ratio
      Data List
      • AFS Voltage

      • O2S

      • Fuel System Status

    4. Engine

      Engine assembly
      Main cause of malfunction
      • Compression loss

      • Accumulation of deposits

        (Combustion chamber, intake valve or intake manifold)

      Problem symptom
      • Engine speed fluctuation due to abnormal combustion

      • Idle speed too low or high

      • Hesitation during acceleration or stalling

      Data List
      • Compression Leakage Count

      • Rough Idle Status

      • Plural Cylinders Rough Idle

      • Rough Idle #1

      • Rough Idle #2

      • Rough Idle #3

      • Rough Idle #4

      Tech Tips


      • If deposits have accumulated in the combustion chamber or on an intake valve, the engine may stall when deposits are caught on an intake valve.

      • When performing the Active Test "Check the Cylinder Compression", if the speed of one cylinder is higher than the others, the cylinder may have a compression loss.

      • If deposits accumulate on the intake valves, the supply of fuel may be delayed due to adherence of the fuel to the deposits, causing a rough idle.

  2. Data List Items Related to Rough Idling

    Tech Tips

    Depending on the vehicle model, the applicable Data List items may vary. Data List items other than the ones used in the diagnostic procedure are for reference only.


    • Compression Leakage Count

    • Rough Idle Status

    • Plural Cylinders Rough Idle

    • Rough Idle #1

    • Rough Idle #2

    • Rough Idle #3

    • Rough Idle #4

    • ISC Learning Value

    • ISC Flow

    • ISC Feedback Value

    • Electric Load Feedback Val

    • Air Conditioner FB Val

    • Eng Stall Control FB Flow

    • Short FT #1

    • Long FT #1

    • Fuel System Status #1, #2

    • Target Air-Fuel Ratio

    • AF Lambda B1S1

    • A/F Learn Value Idle #1

    • A/F Learn Value Low #1

    • A/F Learn Value Mid1 #1

    • A/F Learn Value Mid2 #1

    • A/F Learn Value High #1

    • MAF

    • AFS Voltage B1S1

    • O2S B1S1

    • Engine Speed

PROCEDURE


  1. INTERVIEW THE CUSTOMER


    1. Interview the customer for details about the conditions when the rough idle occurred.

      Tech Tips

      Depending on the conditions when the rough idle occurred, a malfunction in one of the following areas is suspected.

      Problem Symptom Suspected Area
      Hesitation or lack of power occurs during acceleration, regardless of whether engine is cold or warm
      • For low mileage vehicles (ODO reading of less than approximately 20000 km or yearly mileage of less than 2000 km): Fuel quality (degradation, water contamination, etc.)

      • For high mileage vehicles (ODO reading of more than approximately 150000 km): Excessively lean air fuel ratio during acceleration due to deposits in intake system or combustion chamber caught temporarily on intake or exhaust valve or adherence of fuel to the deposits

      • Abnormal mass air flow meter sub-assembly output due to existence of foreign matter

      • Decrease in fuel injector assembly injection volume due to low quality fuel

      Engine stalls or is difficult to start immediately after engine stalled, regardless of whether engine is cold or warm Deposits in intake system or combustion chamber caught temporarily on intake or exhaust valve

      • When decelerating vehicle to a stop, engine speed drops momentarily and vehicle shudders

      • When moving shift lever from N to D or R, or operating air conditioning system or any electrical components, engine speed fluctuates and vehicle shudders

      Temporary deviation in the electrical throttle system idle speed control due to external factors (fuel quality, air conditioning system (environmental causes or low refrigerant pressure), charging system (battery deterioration or low power generation by the alternator) or brake booster system)
      Result
      Proceed to
      NEXT

    NEXT
  2. CHECK DTC OUTPUT


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Perform a road test.

    5. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

    6. Read the DTCs.


      Powertrain > Engine > Trouble Codes
      Result
      Result Proceed to
      DTCs are not output A

      DTC is output

      (DTCs other than P1603, P1604 or P1605 are output)

      B

    B
    A
  3. SYMPTOM CONFIRMATION


    1. Check if the problem symptoms reported in the customer problem analysis recur.

      Tech Tips

      If the problem symptoms do not recur, attempt to reproduce the conditions when the malfunction occurred based on the result of the customer problem analysis.

      Result
      Result Proceed to
      The problem symptom recurs A
      The problem symptom does not recur (occurred in the past) B

    B
    A
  4. READ VALUE USING GTS (ISC LEARNING VALUE)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / ISC Learning Value.


      Powertrain > Engine > Data List
      Tester Display
      ISC Learning Value
    5. Read the value displayed on the GTS.

      Result
      Result Proceed to
      Less than 5.6 L/s A
      Other than above B

    B
    A
  5. READ VALUE USING GTS (SHORT FT AND LONG FT)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Short FT and Long FT.

    5. Read the value displayed on the GTS.

      Result
      Data List Result Proceed to
      Short FT + Long FT -15% or higher, or less than 15% A
      Other than above B

      Tech Tips


      • "Total FT" is used to detect an abnormal air fuel ratio. As the value of "Total FT" is corrected by the ECM before it is displayed in the Data List, the displayed value may not be equal to the sum of the measured "Short FT" and "Long FT".

      • An abnormally lean or rich tendency can be checked by reading the following Data List items: A/F Learn Value Idle, A/F Learn Value Low, A/F Learn Value Mid1, A/F Learn Value Mid2 and A/F Learn Value High. (For vehicles equipped with a V type engine, check that both banks have the same correction tendency.) If the correction of either bank is -15% or less or +15% or more, the air fuel ratio sensor or heated oxygen sensor of that bank may be malfunctioning.

      • The following may cause a lean air fuel ratio (an operating range in which the air fuel ratio learned value correction is +15% or more):


        1. Decrease in fuel injector assembly injection volume

        2. Decrease in mass air flow meter sub-assembly output (due to existence of foreign matter)

        3. Air leaks in intake system after mass air flow meter sub-assembly

        4. Decrease in fuel pressure (at fuel filter, fuel pump or fuel pressure regulator assembly)

      • On vehicles which the learning value for each operating range can be checked, if the value of "A/F Learn Value High" only is corrected to the positive side, a malfunction in the fuel system (clogging of the fuel pump or fuel filter) is suspected.

      • On vehicles which the learning value for each operating range can be checked, if the value of "A/F Learn Value Idle" or "A/F Learn Value Low" only is corrected to the positive side, an air leak after the mass air flow meter sub-assembly is suspected.

      • The following may cause a rich air fuel ratio (an operating range in which the air fuel ratio learned value correction is -15% or less):


        1. Increase in the fuel injector assembly injection volume

        2. Purge VSV system


    B
    A
  6. PERFORM ACTIVE TEST USING GTS (CONTROL THE CYLINDER FUEL CUT)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Start the engine.

      Tech Tips

      Reproduce the vehicle conditions when the malfunction occurred (such as after the engine is warmed up or after a cold start).

    5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Cylinder Fuel Cut / All Data / Engine Speed.


      Powertrain > Engine > Active Test
      Active Test Display
      Control the Cylinder Fuel Cut
      Data List Display
      Engine Speed
    6. According to the display on the GTS, perform the Active Test and check for a malfunctioning cylinder.

      Tech Tips


      • Perform fuel-cut for each cylinder and check the change in the engine speed.

      • If the engine speed of a cylinder does not change while performing the Active Test, it can be determined that the cylinder is malfunctioning.

      • If the engine speed of all cylinders change while performing the Active Test, it can be determined that multiple cylinders are malfunctioning.

      • A cylinder for which the Data List item "Cylinder Misfire Count" increases may be malfunctioning.

      • If "Compression Leakage Count" in the Data List increases, misfiring due to insufficient compression may be occurring.

      Result
      Result Proceed to
      One cylinder is malfunctioning A
      Multiple or all cylinders are malfunctioning, or the malfunctioning cylinder cannot be determined. B

    B
    A
  7. PERFORM ACTIVE TEST USING GTS (CHECK THE CYLINDER COMPRESSION)

    Tech Tips

    If the vehicle does not support the Active Test "Check the Cylinder Compression", measure the compression pressure. If the compression pressure is normal, go to step 8.


    1. Warm up the engine.

    2. Turn the ignition switch off.

    3. Connect the GTS to the DLC3.

    4. Turn the ignition switch to ON.

    5. Turn the GTS on.

    6. Enter the following menus: Powertrain / Engine and ECT / Active Test / Check the Cylinder Compression.


      Powertrain > Engine and ECT > Active Test
      Tester Display
      Check the Cylinder Compression

      Tech Tips

      To display the entire Data List, press the pull down menu button next to Primary. Then select Compression.

    7. While the engine is not running, press the RIGHT or LEFT button to change Check the Cylinder Compression to ON.

      Tech Tips

      After performing the above procedure, Check the Cylinder Compression will start. Fuel injection for all cylinders is prohibited and each cylinder engine speed measurement enters standby mode.

    8. Crank the engine for about 10 seconds.

    9. Monitor the engine speed (Engine Speed of Cyl and Av Engine Speed of All Cyl) displayed on the GTS.

      Tech Tips

      At first, the GTS displays extremely high cylinder engine speed values. After approximately 10 seconds of engine cranking, each cylinder engine speed measurement will change to the actual engine speed.

      Note


      • Do not crank the engine continuously for 20 seconds or more.

      • If it is necessary to crank the engine again after Check the Cylinder Compression has been changed to ON and the engine has been cranked once, press Exit to return to the Active Test menu screen. Then change Check the Cylinder Compression to ON and crank the engine.

      • Use a fully-charged battery.

    10. Stop cranking the engine, and then change "Check the Cylinder Compression" to OFF after the engine stops.

      Note


      • If the Active Test is changed to OFF while the engine is being cranked, the engine will start.

      • When performing the Active Test, DTC P1604 (Startability Malfunction) may be stored.

      • After performing the Active Test, make sure to check and clear DTCs.

    11. Read the value.

      Tech Tips


      • If the value of Data List item "Engine Speed of Cyl" of a cylinder is higher than other cylinders, the cylinder may be malfunctioning.

      • If the value of Data List item "Engine Speed of Cyl" is high for only one cylinder, compression loss is suspected.

      Result
      Result Proceed to

      There is no variation in "Engine Speed of Cyl"

      (All cylinders display approximately the same value for "Engine Speed of Cyl")

      A

      There is variation in "Engine Speed of Cyl"

      (Only one cylinder displays a value for "Engine Speed of Cyl" that differs considerably)

      B

    B
    A
  8. PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Start the engine and warm it up until the engine coolant temperature 75°C (167°F) or higher with all the accessories switched off.

    5. Idle the engine.

    6. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.


      Powertrain > Engine > Active Test
      Tester Display
      Control the Injection Volume
    7. According to the display on the GTS, perform the Active Test and check the vehicle conditions when increasing and decreasing the fuel injection volume.

      Tech Tips

      Change the fuel injection volume between the minimum and maximum range of correction (e.g. -12.5% to 12.5%).

      Result
      Result Proceed to
      Malfunction is still present even if the fuel injection volume is changed A
      Malfunction disappears when the fuel injection volume is changed B

    B
    A
  9. CHECK IGNITION SYSTEM


    1. Check the ignition system.

      Tech Tips


      • Interchange the ignition coil assembly and spark plug of the malfunctioning cylinder with those of a known good cylinder and check if the malfunctioning cylinder returns to normal.

      • If the spark plug of the malfunctioning cylinder is abnormally wet with fuel even after the ignition coil assembly and spark plug are replaced, a leaking fuel injector assembly is suspected.

      Result
      Result Proceed to
      The malfunctioning cylinder does not return to normal A
      The malfunctioning cylinder returned to normal B

    B
    A
  10. INSPECT OTHER RELATED COMPONENTS


    1. Check the ignition coil assembly power source circuit, wire harness and connectors.

      Result
      Proceed to
      NEXT

    NEXT
  11. REMOVE FOREIGN OBJECT (CLEAN THROTTLE BODY WITH MOTOR ASSEMBLY)


    1. Clean off any deposits from the inside of the throttle body with motor assembly.

    2. Push open the throttle valve and wipe off any carbon from the valve and bore using a piece of cloth soaked in non-residue solvent.

      B0069DXC01
      *1 Throttle Body with Motor Assembly *2 Bore
      *3 Valve - -
      *a Reference *b Throttle Body with Motor Assembly Cross-section Diagram
      *c When valve fully opened *d Do not directly apply cleaner
      *e Deposits - -

      Note


      • Make sure that the cloth or your fingers do not get caught in the valve.

      • Make sure that foreign matter does not enter the throttle valve.

      • Do not directly apply non-residue solvent to the throttle body with motor assembly or wash the throttle body with motor assembly. Cleaning solvent may leak into the motor from the shaft and cause problems such as rust or valve movement problems.

      • If there is coating material on the edge of the valve, be careful not to remove it.

      Tech Tips

      The illustrations are for reference only. Actual parts may differ.

      Result
      Proceed to
      NEXT

    NEXT
  12. PERFORM CONFIRMATION DRIVING PATTERN


    1. Perform "Inspection After Repair" after cleaning the throttle body with motor assembly.

      Click here

    2. Connect the GTS to the DLC3.

    3. Turn the ignition switch to ON.

    4. Turn the GTS on.

    5. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

    6. Allow the engine to idle for 3 minutes or more and confirm that the engine speed is within the specified range.

      Tech Tips

      If the engine is operated without performing learning value reset and idle learning after cleaning the deposits from the throttle body with motor assembly, the idle speed may increase.

      Result
      Proceed to
      NEXT

    NEXT
  13. CHECK CYLINDER COMPRESSION PRESSURE


    1. Measure the cylinder compression pressure. If the compression pressure of a cylinder is low, inspect the engine assembly and repair or replace parts as necessary.

      Click here

      Result
      Proceed to
      NEXT

    NEXT
  14. REPLACE FUEL INJECTOR ASSEMBLY


    1. Replace the fuel injector assembly of the malfunctioning cylinder.

      Click here

      Tech Tips


      • If the air fuel ratio learned value is corrected to the positive side for all operating ranges due to low fuel injector assembly injection volume, replace the fuel injector assemblies of all cylinders.

      • Perform "Inspection After Repair" after replacing the fuel injector assembly.

        Click here

      Result
      Proceed to
      NEXT

    NEXT
  15. READ VALUE USING GTS (MAF)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Start the engine and warm it up until the engine coolant temperature 75°C (167°F) or higher with all the accessories switched off.

    5. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.


      Powertrain > Engine > Data List
      Tester Display
      MAF
    6. According to the display on the GTS, read the Data List when the engine is running.

      Result
      Result Proceed to

      Idling (warmed up engine, without load): 1.0 to 5.0 gm/sec

      Engine speed 2000 rpm (warmed up engine, without load): 5.0 to 9.0 gm/sec

      Engine speed 3000 rpm (warmed up engine, without load): 9.0 to 15.0 gm/sec

      A
      Other than below B

    B
    A
  16. PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Start the engine and warm it up until the engine coolant temperature 75°C (167°F) or higher with all the accessories switched off.

    5. Warm up the air fuel ratio sensor at an engine speed of 2500 rpm for 90 seconds.

    6. Idle the engine.

    7. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / All Data / AFS Voltage B1S1 and O2S B1S2.


      Powertrain > Engine > Active Test
      Active Test Display
      Control the Injection Volume for A/F Sensor
      Data List Display
      AFS Voltage B1S1
      O2S B1S2
    8. According to the display on the GTS, perform the Active Test and check the vehicle conditions when increasing and decreasing the fuel injection volume.

      Note


      • The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.

      • Read the output voltage immediately after warming up the air fuel ratio sensor and heated oxygen sensor to avoid an inaccurate reading due to a sensor cooling.

      Tech Tips

      The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 12.5%.

      Result

      GTS Display

      (Sensor)

      Injection Volume Voltage

      AFS Voltage B1S1

      (Air fuel ratio)

      12.5% Below 3.1 V
      -12.5% Higher than 3.4 V

      O2S B1S2

      (Heated oxygen)

      12.5% Higher than 0.55 V
      -12.5% Below 0.4 V
      Result
      Result Proceed to
      Output voltage values are abnormal A
      Malfunction disappears when fuel injection volume is increased B
      Malfunction is still present when fuel injection volume is increased, even if output voltage values are normal C

    B
    C
    A
  17. REPLACE AIR FUEL RATIO SENSOR AND HEATED OXYGEN SENSOR


    1. Replace the air fuel ratio sensor.

      Click here

      Tech Tips

      Perform "Inspection After Repair" after replacing the air fuel ratio sensor.

      Click here

    2. Replace the heated oxygen sensor.

      Click here

      Result
      Proceed to
      NEXT

    NEXT
  18. REPLACE FUEL INJECTOR ASSEMBLY


    1. Replace the fuel injector assemblies of all cylinders.

      Click here

      Tech Tips

      Perform "Inspection After Repair" after replacing the fuel injector assembly.

      Click here

      Result
      Proceed to
      NEXT

    NEXT
  19. CHECK INTAKE SYSTEM


    1. Check for air leaks or blockage in the intake system components. If a connection problem or foreign matter is found, repair the connection or remove the foreign matter.

      Tech Tips


      • If there is foreign matter in the intake system components, remove it before proceeding to the next step.

      • If there is no foreign matter in the intake system components, check for foreign matter in the mass air flow meter sub-assembly. If there is foreign matter in the mass air flow meter sub-assembly, remove it.

      Result
      Proceed to
      NEXT

    NEXT
  20. INSPECT OTHER RELATED COMPONENTS


    1. Inspect other related components.

      Tech Tips

      If the malfunctioning part could not be determined by performing the preceding inspections, one of the following malfunctions is suspected.


      • Engine mount deterioration

      • Deposits in the intake manifold or on an intake valve

      • Delay in fuel supply due to adherence of the fuel to the deposits

      Result
      Proceed to
      NEXT

    NEXT
  21. REPAIR OR REPLACE MALFUNCTIONING PARTS


    1. Repair or replace the malfunctioning part.

    2. Perform "Inspection After Repair" after repairing or replacing the malfunctioning part.

      Result
      Proceed to
      NEXT

    NEXT
  22. CONDUCT CONFIRMATION TEST


    1. Check that the idle has returned to normal.

      Result
      Proceed to
      NEXT

    NEXT