Lexus ES: Rough Idling

HINT:

• If any DTCs are output, perform troubleshooting for the DTCs first.
• Try 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.

• Mass Air Flow Sensor
• Engine Stall Control F/B Flow
• Target Fuel Pressure (High)
• Target Fuel Pressure (Low) / Target Fuel Pressure 2
• Fuel Pressure (High)
• Fuel Pressure (Low) / Fuel Pressure 2
• Fuel Pump Control Duty Ratio
• High Pressure Fuel Pump Duty Ratio (D4)
• High Pressure Fuel Pump Discharge Rate
• Target Air-Fuel Ratio
• A/F (O2) Sensor Current B1S1
• A/F (O2) Sensor Current B1S2
• Short FT B1S1
• Long FT B1S1
• Total FT Bank 1
• Fuel System Status Bank 1
• A/F Learn Value Idle (Port) Bank 1
• A/F Learn Value Low (Port) Bank 1
• A/F Learn Value Mid No.1 (Port) Bank 1
• A/F Learn Value Mid No.2 (Port) Bank 1
• A/F Learn Value High (Port) Bank 1
• 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
• Target EGR Valve Position No.1
• EGR Step Position
• Misfire Count Cylinder #1 to #4
• ISC Learning Value

HINT:

• "Total FT Bank 1" is used to detect an abnormal air fuel ratio. As the value of "Total FT Bank 1" 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 B1S1" and "Long FT B1S1".
• An abnormally lean or rich tendency can be checked by reading the following Data List items: A/F Learn Value Idle (Port) Bank 1, A/F Learn Value Low (Port) Bank 1, A/F Learn Value Mid (Port) No.1 Bank 1, A/F Learn Value Mid (Port) No.2 Bank 1, A/F Learn Value High (Port) Bank 1, 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 and A/F Learn Value High Bank 1. (For vehicles equipped with a V type engine, check that both banks have the same correction tendency. If the correction of either bank is -20% or less or +20% or more, the air fuel ratio sensor (sensor 1) or air fuel ratio sensor (sensor 2) 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 +20% 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, fuel main valve assembly or fuel suction plate sub-assembly)
• On vehicles which the learning value for each operating range can be checked, if the value of "A/F Learn Value High (Port) Bank 1" or "A/F Learn Value High Bank 1" 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 (Port) Bank 1", "A/F Learn Value Low (Port) Bank 1", "A/F Learn Value Idle Bank 1"or "A/F Learn Value Low Bank 1" only is corrected to the positive side, an air leak after the mass air flow meter sub-assembly is suspected.
• 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 filter is suspected.
• The following may cause a rich air fuel ratio (an operating range in which the air fuel ratio learned value correction is -20% or less):
  1. Increase in the fuel injector assembly injection volume
  2. Purge VSV system

HINT:

• 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 items "Misfire Count Cylinder #1 to #4" increases may be malfunctioning.

NOTICE:

• If the Check the Cylinder Compression Active Test needs to be performed after it is changed to "Start" and performed once, press the Exit button to return to the Active Test menu screen. Then perform the Check the Cylinder Compression Active Test again.
• As soon as the measurements are obtained, stop the Active Test.

HINT:

• At first, the Techstream display will show each cylinder's engine speed measurement to be extremely high. After the engine has started, each cylinder's engine speed measurement will change to the actual engine speed.
• If the cylinder engine speed values (Engine Speed Cylinder #1 to #4) displayed in the Data List do not change from an extremely high value, return to the Active Test menu screen, change "Check the Cylinder Compression" to "Start" and crank the engine again within 1 second.

NOTICE:

• When performing the Active Test, DTC may be stored.
• After performing the Active Test, make sure to check and clear the DTCs.

HINT:

• If the value of Data List item "Engine Speed Cylinder" of a cylinder is higher than other cylinders, the cylinder may be malfunctioning.
• If the value of Data List item "Engine Speed Cylinder" is high for only one cylinder, compression loss is suspected.

HINT:

• Increase and decrease the fuel injection volume of the port injection and direct injection simultaneously and check the vehicle condition.
• Change the fuel injection volume between the minimum and maximum range of correction (e.g. -12.5% to 24.8%).

HINT:

• 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.

HINT:

• 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.
• If the symptoms tend to improve by decreasing the fuel injection amount, the engine misfire may be due to blockage of an EGR port leading to EGR becoming excessive to the cylinders with little EGR port blockage.
• Perform "Inspection After Repair" after replacing the fuel injector assembly.

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NOTICE:

• Make sure that the value of Data List item Engine Independent is "Operate" while performing the Active Test.
• Do not leave the EGR valve open for 10 seconds or more during the Active Test.
• Be sure to return the EGR valve to step 0 when the Active Test is completed.
• Do not open the EGR valve 30 steps or more during the Active Test.

HINT:

• If the value of Data List item Engine Independent is "Not Opr" when the engine is idling, charge control is being performed. Perform the Active Test after charge control is complete ("Operate" is displayed).
• While performing the Active Test, if the increase in the value of Intake Manifold Absolute Pressure is small, the EGR valve assembly may be malfunctioning.
• Even if the EGR valve assembly is malfunctioning, rough idling or an increase in the value of Intake Manifold Absolute Pressure may occur while performing the Active Test. However, the amount that the value of Intake Manifold Absolute Pressure increases will be smaller than normal.

NOTICE:

• The air fuel ratio sensor (sensor 1) has an output delay of a few seconds and the air fuel ratio sensor (sensor 2) has a maximum output delay of approximately 20 seconds.
• Read the output value immediately after warming up the air fuel ratio sensor (sensor 1) and air fuel ratio sensor (sensor 2) to avoid an inaccurate reading due to a sensor cooling.

HINT:

• Increase and decrease the fuel injection volume of the port injection and direct injection simultaneously and check the vehicle condition.
• The Active Test "Control the Injection Volume for A/F Sensor" can be used to lower the fuel injection volume by 12.5% or increase the injection volume by 12.5%.

NOTICE:

• 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. Non-residue 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 throttle valve, be careful not to remove it.

• Engine mount deterioration
• Deposits in the intake manifold or on an intake valve
• EGR distribution is poor due to EGR port blockage
• Delay in fuel supply due to adherence of the fuel to the deposits

HINT:

• 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.

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