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Home >> Lexus >> 2021 >> RC F Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Symptom Tests (2 Of 2) >> SFI System >> Engine Stalls [09/2014 - 11/2017] >> Description
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Engine Stalls [09/2014 - 11/2017]: 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 (for port injection)
  • Fuel injector assembly (for direct injection)
  • Fuel pump (for low pressure side)
  • Fuel pump (for high pressure side)
  • 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 control motor
  • 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
  • Engine mount
High load from another system
  • Air conditioning system
  • Power steering system
  • Electrical load signal system
  • A/T system

HINT: 

  1. SYMPTOM AND CAUSE OF SYSTEM MALFUNCTION 

    HINT: 

    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
      Data List Cylinder Misfire Count
      HINT: 
      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
      Data List Cylinder Misfire Count
    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 #1 (#2)
      • Long FT #1 (#2)
      • Fuel System Status #1 (#2)
      • Target Air-Fuel Ratio
      • AF Lambda B1S1 (B2S1)
      • A/F Learn Value Idle #1 (#2)
      • A/F Learn Value Low #1 (#2)
      • A/F Learn Value Mid1 #1 (#2)
      • A/F Learn Value Mid2 #1 (#2)
      • A/F Learn Value High #1 (#2)
      • A/F Learn Val Low #1 (Dual) (#2 (Dual))
      • A/F Learn Val Mid1 #1 (Dual) (#2 (Dual))
      • A/F Learn Val Mid2 #1 (Dual) (#2 (Dual))
      • A/F Learn Val High #1 (Dual) (#2 (Dual))
      • Total FT #1 (#2)
      HINT: 
      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.
      PURGE VSV

      Main cause of malfunction Purge VSV stuck open
      Symptom Engine speed fluctuation due to abnormal combustion
      Data List
      • EVAP (Purge) VSV
      • Evap Purge Flow
      • Purge Density Learn Value
      • EVAP Purge VSV
      • Purge Cut VSV Duty
      FUEL SYSTEM

      HINT: 
      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
      HINT: 
      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 B1S1 (B2S1)
      • O2S B1S2 (B2S2)
      • Fuel System Status #1 (#2)
    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
      HINT: 
      • 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.
      VVT

      Main cause of malfunction Camshaft timing control motor stuck to advance side or camshaft timing oil control valve assembly stuck open
      Symptom Abnormal combustion due to excessive valve overlap
      Data List
      • VVT Advance Fail
      • VVT Change Angle #1 (#2)
      • VVT-iE Duty #1 (#2)
      • VVT-iE Mot Direction #1 (#2)
      • VVT Target Angle #1 (#2)
      • VVT Ex Hold Lrn Val #1 (#2)
      • VVT Ex Chg Angle #1 (#2)
      • VVT Ex OCV Duty #1 (#2)
  2. Data List Items Related to Engine Stalls 

    HINT: 

    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.

    • ISC Learning Value
    • ISC Flow
    • ISC Feedback Value
    • Electric Load Feedback Val
    • Air Conditioner FB Val
    • Eng Stall Control FB Flow
    • Short FT #1 (#2)
    • Long FT #1 (#2)
    • Fuel System Status #1 (#2)
    • Target Air-Fuel Ratio
    • AF Lambda B1S1 (B2S1)
    • A/F Learn Value Idle #1 (#2)
    • A/F Learn Value Low #1 (#2)
    • A/F Learn Value Mid1 #1 (#2)
    • A/F Learn Value Mid2 #1 (#2)
    • A/F Learn Value High #1 (#2)
    • A/F Learn Val Low #1 (Dual) (#2 (Dual))
    • A/F Learn Val Mid1 #1 (Dual) (#2 (Dual))
    • A/F Learn Val Mid2 #1 (Dual) (#2 (Dual))
    • A/F Learn Val High #1 (Dual) (#2 (Dual))
    • Total FT #1 (#2)
    • Fuel Press
    • Fuel Pressure Target Value
    • Fuel Pump Duty (D4)
    • Fuel Pump2 Duty (D4)
    • MAF
    • Cylinder Misfire Count #1 (to #8)
    • AFS Voltage B1S1 (B2S1)
    • O2S B1S2 (B2S2)
    • Engine Speed
    • Shift SW Status (D Range)
    • SPD (NT)
    • SPD (NO)
    • VVT-iE Duty #1 (#2)
    • VVT-iE Mot Direction #1 (#2)
    • VVT Target Angle #1 (#2)
    • VVT Advance Fail
    • VVT Change Angle #1 (#2)
    • VVT OCV Duty #1 (#2)
    • VVT Ex Hold Lrn Val #1 (#2)
    • VVT Ex Chg Angle #1 (#2)
    • VVT Ex OCV Duty #1 (#2)