Engine Difficult to Start [12/2021 - ]: Description

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	Misfire Count Cylinder #1 to #6
   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	Misfire Count Cylinder #1 to #6

2. Fuel system
   FUEL INJECTOR ASSEMBLY
   
   

   Main cause of malfunction	Blockage, leak
   Problem symptom	Engine speed fluctuation due to abnormal combustion Idle speed too low or high Engine is difficult to start due to high concentration of HC
   Data List	Target Air-Fuel Ratio Short FT B1S1, B2S1 Long FT B1S1, B2S1 Total FT Bank 1, Bank 2 Fuel System Status Bank 1, Bank 2 A/F Learn Value Idle Bank 1, Bank 2 A/F Learn Value Low Bank 1, Bank 2 A/F Learn Value Mid No. 1 Bank 1, Bank 2 A/F Learn Value Mid No. 2 Bank 1, Bank 2 A/F Learn Value High Bank 1, Bank 2 A/F Learn Value Idle (Port) Bank 1, Bank 2 A/F Learn Value Low (Port) Bank 1, Bank 2 A/F Learn Value Mid No. 1 (Port) Bank 1, Bank 2 A/F Learn Value Mid No. 2 (Port) Bank 1, Bank 2 A/F Learn Value High (Port) Bank 1, Bank 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. If the engine is difficult to start only when the vehicle has been left as is for a long time, a leaking fuel injector assembly is suspected.

   FUEL SYSTEM
   
   

   Main cause of malfunction	Fuel suction plate sub-assembly or fuel main valve assembly malfunction
   Problem symptom	Engine is difficult to start due to insufficient fuel supply
   HINT:  If the fuel suction plate sub-assembly or fuel main valve assembly cannot maintain residual pressure, fuel vaporization or air intrusion may occur, causing starting difficulty. 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 assembly 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 Lack of power

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 Sensor Bank1, Bank 2
   HINT:  If the value of the Data List item "MAF Sensor Bank1, Bank 2" 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 Lack of power
   Data List	Engine Stall Control F/B Flow ISC F/B Learn Torque ISC Total AUXS Torque ISC F/B Torque Sum of ISC F/B Torque (Recent) ISC AUXS Torque (Alternator) ISC AUXS Torque (Air Conditioner) Throttle Air Flow F/B Value

   AIR FUEL RATIO SENSOR (SENSOR 1), AIR FUEL RATIO SENSOR (SENSOR 2)
   
   

   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	A/F (O2) Sensor Current B1S1, B2S1 A/F (O2) Sensor Current B1S2, B2S2 Fuel System Status Bank 1, Bank 2

4. Engine
   ENGINE ASSEMBLY
   
   

   Main cause of malfunction	Compression loss Accumulation of deposits (Combustion chamber, intake valve, exhaust 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 or exhaust valve, the engine may stall when deposits are caught on an intake or exhaust 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 or exhaust valves, the supply of fuel may be delayed due to adherence of the fuel to the deposits, causing a rough idle.

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.

• MAF Sensor Bank1, Bank 2
• Engine Stall Control F/B Flow
• ISC F/B Learn Torque
• ISC Total AUXS Torque
• ISC F/B Torque
• Sum of ISC F/B Torque (Recent)
• ISC AUXS Torque (Alternator)
• ISC AUXS Torque (Air Conditioner)
• Throttle Air Flow F/B Value
• Target Fuel Pressure (High)
• Target Fuel Pressure (Low) / Target Fuel Pressure 2
• Fuel Pressure (High)
• Fuel Pressure (Low) / Fuel Pressure 2
• High Pressure Fuel Pump Duty Ratio (D4)
• High Pressure Fuel Pump Discharge Rate
• Target Air-Fuel Ratio
• A/F (O2) Sensor Current B1S1, B2S1
• A/F (O2) Sensor Current B1S2, B2S2
• Short FT B1S1, B2S1
• Long FT B1S1, B2S1
• Total FT Bank 1, Bank 2
• Fuel System Status Bank 1, Bank 2
• A/F Learn Value Idle Bank 1, Bank 2
• A/F Learn Value Low Bank 1, Bank 2
• A/F Learn Value Mid No. 1 Bank 1, Bank 2
• A/F Learn Value Mid No. 2 Bank 1, Bank 2
• A/F Learn Value High Bank 1, Bank 2
• A/F Learn Value Idle (Port) Bank 1, Bank 2
• A/F Learn Value Low (Port) Bank 1, Bank 2
• A/F Learn Value Mid No. 1 (Port) Bank 1, Bank 2
• A/F Learn Value Mid No. 2 (Port) Bank 1, Bank 2
• A/F Learn Value High (Port) Bank 1, Bank 2
• Misfire Count Cylinder #1 to #6

HINT: 

The frequency of the malfunction can be determined by confirming the number of times the symptom occurred.

• Engine Difficult to Start Count (Engine Starting Time Long)
• Engine Difficult to Start Count (Immobiliser)
• Engine Difficult to Start Count (Engine Stall Immediately After Starting)