Engine Difficult to Start [10/2014 - 09/2017]: 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 direct injection) Fuel injector assembly (for port injection) Fuel pump (for high pressure side) Fuel pump (for low pressure side) Fuel pump control circuit Fuel suction plate sub-assembly Fuel main valve assembly 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 with motor body assembly Air fuel ratio sensor Heated oxygen sensor Cam timing oil control solenoid assembly Camshaft timing oil control valve assembly Variable Valve Timing system (VVT-iW 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 Automatic transaxle system

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.

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.

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 #4
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 #4

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	Short FT Bank 1 Long FT Bank 1 Fuel System Status Bank 1 Target Air-Fuel Ratio A/F (O2) Lambda Sensor B1S1 A/F Learn Value Idle Bank 1 A/F Learn Value Low Bank 1 A/F Learn Value Mid No. 1 Bank 1 A/F Learn Value Mid No. 2 Bank 1 A/F Learn Value High Bank 1 A/F Learn Value Low (Dual) Bank 1 A/F Learn Value Mid (Dual) No. 1 Bank 1 A/F Learn Value Mid (Dual) No. 2 Bank 1 A/F Learn Value High (Dual) Bank 1 Total FT Bank 1
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 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

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	Mass Air Flow Sensor
HINT: If the value of the Data List item "Mass Air Flow Sensor" 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	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, 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	A/F (O2) Sensor Voltage B1S1 O2 Sensor Voltage B1S2 Fuel System Status Bank 1

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.

Data List Items Related to Engine Difficult to Start
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.
- 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
- Short FT Bank 1
- Long FT Bank 1
- Fuel System Status Bank 1
- Target Air-Fuel Ratio
- A/F (O2) Lambda Sensor B1S1
- A/F Learn Value Idle Bank 1
- A/F Learn Value Low Bank 1
- A/F Learn Value Mid No. 1 Bank 1
- A/F Learn Value Mid No. 2 Bank 1
- A/F Learn Value High Bank 1
- A/F Learn Value Low (Dual) Bank 1
- A/F Learn Value Mid (Dual) No. 1 Bank 1
- A/F Learn Value Mid (Dual) No. 2 Bank 1
- A/F Learn Value High (Dual) Bank 1
- Total FT Bank 1
- Fuel Pressure (High)
- High Pressure Fuel Pump Duty Ratio (D4)
- Target Fuel Pressure (High)
- High Pressure Fuel Pump Discharge Rate
- Mass Air Flow Sensor
- Misfire Count Cylinder #1 to #4
- A/F (O2) Sensor Voltage B1S1
- O2 Sensor Voltage B1S2