Rough Idling [11/2016 - ]: Description

HINT: 

• 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 Techstream, 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 

   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 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 A/F Learn Val Low (Dual) A/F Learn Val Mid1 (Dual) A/F Learn Val Mid2 (Dual) A/F Learn Val High (Dual) Total FT
      HINT:  If the engine malfunction disappears when the fuel injection volume is increased or decreased by performing the Active Test "Control the Injection Volume" or "Control the Injection Volume for A/F Sensor", the respective cylinder may be malfunctioning.

      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
      EGR SYSTEM
      
      

      Main cause of malfunction	EGR valve movement problems or stuck
      Problem symptom	Engine speed fluctuation due to abnormal combustion Idle speed too low or high Startability malfunction, lack of power or engine stalls
      Data List	EGR Step Position Target EGR Position Normally, Actual EGR Position = Target EGR Position +/-5% (fully closed: 0%, fully open: 100%) When the power switch is turned on (IG), the EGR valve fully closes.

      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 Deposit Loss 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
      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.

2. Data List Items Related to Rough Idling 

   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
   • Deposit Loss Flow
   • Fuel Press
   • Fuel Pressure Target Value
   • Fuel Pump Duty (D4)
   • HP FP Discharge Rate
   • 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
   • A/F Learn Val Low (Dual)
   • A/F Learn Val Mid2 (Dual)
   • A/F Learn Val Mid1 (Dual)
   • A/F Learn Val High (Dual)
   • Total FT
   • MAF
   • Target EGR Position
   • EGR Step Position
   • Cylinder Misfire Count
   • AFS Voltage
   • O2S