2018 Ford Explorer V6 3.5L – Low/Slow Idle

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The 2018 Ford Explorer V6 3.5L has also been reported to experience a "Slow Idle" or "Low Idle" issue, where the engine idle speed drops below the expected range, particularly when stopped or at low speeds. This condition can lead to noticeable vibrations, difficulty maintaining a steady idle, and stalling, especially when accessories such as air conditioning are in use.

Common causes of a low idle include a dirty throttle body, malfunctioning idle air control valve, clogged PCV system, or insufficient airflow due to intake air leaks. Addressing these potential causes through systematic troubleshooting can help restore proper idle speed and ensure smoother engine operation.

Procedure

A. Automatic Transmission

1. Perform the torque converter operation test for any concerns.

B. Fuel Delivery System

1. Verify the Fuel System Integrity

• Perform a visual inspection of all components in the fuel system, including:
  a. Fuel lines and connections
  b. Relays
  c. Fuel tank
  d. Fuel pump
  e. Fuel pressure regulator
  f. Fuel rail
  g. Connector pins for any signs of damage
  h. Electrical connectors to ensure they are securely connected
  
• Confirm that the vehicle adheres to its maintenance schedule, particularly replacing the fuel filter every 30,000 miles (48,280 km).
  
• Check the functionality of the Inertia Fuel Shutoff (IFS) switch.
  
• Inspect the fuses to ensure they are in good condition.
  
• Ensure the battery is fully charged.
  
• Use clean and high-quality fuel to maintain optimal performance.
  

2. Turn the ignition ON and measure the fuel pressure using a mechanical fuel pressure gauge.
Note: Relieve fuel system pressure and turn the ignition OFF before testing.

3. Inspect for open-circuit issues in both the ground and power circuits of the fuel pump.

4. Examine the ethanol/water separation and gasoline mixture, calculating the ethanol percentage in the fuel.

5. Use a Scan Tool to monitor the FF_INF Parameter ID (PID) and compare it to the calculated ethanol percentage.

6. Reset the ethanol percentage parameter in the Powertrain Control Module (PCM) using a Scan Tool. Verify the FF_LRND (MODE) PID after driving approximately 7 miles (11.3 km).

• Expectation: PID indicates Yes.

7. Reassess the FF_INF Parameter ID (PID) with the Scan Tool and compare it to the calculated ethanol percentage.

• Expectation: within 20%.

8. Inspect for fuel pressure leak-down issues.

• Expectation: MRFS PID stays within 5 psi (34 kPa) or ERFS exceeds 40 psi (275 kPa) after 1 minute.

9. Conduct the Power Balance Test using the Scan Tool.

• Expectation: The test passes.

10. Compare the PCM Live Data FRP (PRESS) PID value to the mechanical fuel pressure gauge indication. Note: Relieve pressure, turn off the ignition, and pressurize the system before comparison.

• Expectation: FRP (PRESS) is within 22 psi (153 kPa) of the gauge reading.

11. Observe fuel pressure during a road test

• Expectation: greater than 51 psi (352 kPa)

12. Inspect for any obstructions in the fuel supply line.

13. Ensure the repair resolves the issue.

14. Confirm proper operation of the PCM.

C. Intake Air System

1. Retrieve the Diagnostic Trouble Codes (DTCs) from the Powertrain Control Module (PCM).

2. Check the idle speed.

3. Check for vacuum leaks in the intake air system from the Mass Airflow (MAF) sensor to the intake manifold such as:

• Damaged or torn intake air ducting.
• Loose fittings where the intake air duct attaches to the air filter housing or throttle body.
• EGR valve gasket leaking into the intake manifold.
• Issues with the intake manifold assembly or gasket.
• Defects in the EGR valve diaphragm or control solenoid.
• Faulty connections or hoses in the vacuum supply.

4. Check for restrictions between the intake air ducting and the throttle body.

5. Check the harness and connection of the Intake Manifold Tuning Valve (IMTV) for any damage.

6. Check the voltage between Pin 1 of the IMTV Actuator connector harness and the negative terminal of the battery.

• Expectation: greater than 10.5V.

7. Check for open-circuit issues between Pin 3 of the IMTV Actuator connector harness and the PCM connector harness.

8. Check for short-to-ground issues between the PCM connector harness and the ground.

9. Check for short-to-voltage issues between Pin 3 of the IMTV Actuator connector harness and the ground.

10. Check the lamp illumination in the Key ON Engine OFF (KOEO) and Key ON Engine Running (KEOR) condition between Pin 1 and Pin 3 of the IMTV Actuator connector harness.

11. Check the operation of the IMTV Actuator manually.

12. Check the functionality of the IMTV Actuator.

13. Check the Intake Manifold Runner Control (IMRC) condition as below:

• Disconnected or damaged linkages.
• Correct connection, damage or leaks between the IMRC solenoid and vacuum line.
• Restricted linkage.
• Proper operation of spring tension.
• Proper operation of IMRC manually.

14. Check for IMRC functionality.

15. Check for open-circuit issues between:

• Pin 2 and Pin 1 of the IMRC Solenoid Bank 1/Bank 2 component.
• Pin 1 of the IMRC Solenoid Bank 1/Bank 2 connector harness and the ground.
• Pin 2 of the IMRC Solenoid Bank 1/Bank 2 connector harness and the PCM.
• Pin 3 and Pin 1 of the IMRC Sensor Bank 1/Bank 2 connector harness.

16. Check for short-to-ground issues between Pin 2 of the IMRC Sensor Bank 1/Bank 2 connector harness and the ground.

17. Check for short-to-voltage issues between Pin 3 of the IMRC Sensor Bank 1/Bank 2 connector harness and the ground.

18. Perform preliminary diagnostics for idle air concerns.

19. Monitor the Intake Air System Parameter IDs (PIDs) such as:

• ECT TEMP and ECT1 TEMP
• ETC_TRIM (ANGL)
• IACTRIM (NUM) and IACKAM2 (NUM)

20. Check PCM operation.

D. Exhaust System

1. Retrieve the Diagnostic Trouble Codes (DTCs) from the Powertrain Control Module (PCM).

2. Check the PCM connector harness condition.

3. Check the Fuel Pressure value.

4. Check Fuel Pressure Sensor operation. NOTE: Testing is performed with the ignition in the KOEO condition, and the Fuel Pump disconnected.

5. Check the exhaust system for leaks or restrictions.

6. Check for excessive exhaust back pressure with anexhaust back pressure tool or manifold vacuum.

7. Perform the catalyst monitor cycle.

E. Charging system

1. Inspect the following charging system items:

• Battery and generator for loose, damaged, corroded connections.
• Engine and battery ground for loose, damaged, corroded connections.
• Battery junction box for loose or corroded connections.
• Verify the fuses and fusible links.
• Inspect wiring, terminals and connectors for any damaged and corroded.

2. Inspect the Front End Accessory Drive (FEAD) system.

3. Check the battery condition and state of charge.

4. Check for abnormal battery drain when ignition OFF.

F. Universal Heated Oxygen Sensor (HO2S)

1. Retrieve the Diagnostic Trouble Codes (DTCs) from the Powertrain Control Module (PCM).

2. Ensure the sensor connectors are connected to the correct bank.

3. Visually inspect the harness condition.

4. Check for misfire event concerns.

5. Check for aftermarket equipment operation concerns.

6. Check for short-circuit issues between Pin 2 of the Universal HO2S harness connector and the ground.

7. Check for open-circuit issues between:

• Pin 4 of the Universal HO2S harness connector and the E50 for HO2S bank 1 (E51 for HO2S bank 2) of the PCM harness connector.
• Pin 5 of the Universal HO2S harness connector and the E20 for HO2S bank 1 (E21 for HO2S bank 2) of the PCM harness connector.
• Pin 2 of the Universal HO2S harness connector and the E79 for HO2S bank 1 (E84 for HO2S bank 2) of the PCM harness connector.

8. Check the voltage between the Pin 1 of the Universal HO2S harness connector and the ground. Note: Connect the PCM connector before testing and turn the ignition ON.

• Expectation: greater than 10.5V.

9. Turn the ignition OFF, and check for open-circuit issues between Pin 2 of the Universal HO2S harness connector and the E79 for HO2S bank 1 (E84 for HO2S bank 2) of the PCM harness connector.

10. Check for short-circuit issues between Pin 2 of the Universal HO2S connector harness and:

• The ground.
• Other Pins of the Universal HO2S connector harness.

11. Check the internal resistance between Pin 1 and Pin 2 of the Universal HO2S component harness.

• Expectation: Measured resistance is between 1.8 – 6 Ohms range.

12. Turn the ignition OFF and disconnect the Universal HO2S and PCM connector; check for short-to-ground and short-to-voltage issues between Pin 4, Pin 5, and Pin 6 of the Universal HO2S connector harness and the ground.

13. Reconnect the PCM connector, turn the ignition ON, and check the voltage between the Pin 5 of the Universal HO2S connector harness and the ground.

• Expectation: between 2.4 – 2.6 V.

14. Carry out the KOER seft-test.

15. Check for llooose connections and damaged or corroded pins of the upstream and downstream HO2S connector.

16. Check the exhaust system for leaks.

17. Check the Universal HO2S for contamination from any of the following items:

• Use the unapproved silicon sealers, and cleaning agents.
• Use the contaminated fuel with lead or silicon additives.
• Excessive oil consumption.
• Leak glycol internally.
• Short the drive cycle in cold.

18. Check the self-test Universal HO2S result using the Scan Tool.

• Expectation: the result is within the range

19. Check PCM operation.

G. Base Engine

1. Check for air leaks in the intake air system; or components and vacuum lines connect to the system (such as Positive Crankcase Ventilation (PCV), Exhaust Gas Recirculation (EGR) valve).

H. Additional Testing

NOTE: The following steps outline the necessary checks to ensure the vehicle operates normally with the ignition turned OFF.

1. Begin by inspecting the battery and charging system voltages.

2. Conduct a PCM Power Relay component test.

3. Turn the ignition ON and measure the voltage between Pin 3 of the PCM Power Relay connector harness and ground.

• Expected result: Above 10.5V.

4. Turn the ignition OFF, then inspect for an open circuit between Pin 1 of the PCM Power Relay connector harness and Pin B20 of the PCM connector. Turn the ignition ON and check for short-to-voltage issues between Pin B20 of the PCM connector and ground.

5. Measure the voltage between Pin B64 of the PCM connector and ground.

• Expected result: Above 10.5V.

6. Turn the ignition OFF and check for an open circuit between Pin 5 of the PCM Power Relay connector harness and Pins B99 and B97 of the PCM connector.

7. Inspect for short-to-ground issues between Pin B20 of the PCM connector and ground.

8. Check for short-to-voltage issues between Pin B64 of the PCM connector and ground.

9. Disconnect the injector and inspect for an open circuit between Pin E18 of the PCM connector and Pin 2 of the injector connector.

10. Use the Scan Tool to observe the INJPWR_M PID value when turning the ignition ON, then OFF.

• Expected result: Change from above 10.5V to 0V.

Additional Procedure for Other Scenarios:

1. Use the Scan Tool to check and clear DTCs from the PCM.

2. Use the Live Data function to select and monitor PIDs related to the suspected system issue.

3. Confirm if any concerns or symptoms appear based on the PID values recorded in Step 2; if so, proceed to Step 7.

4. Attempt to recreate the symptom based on Freeze Frame data; if successful, proceed to Step 7.

5. Recreate symptoms and monitor relevant PIDs during different road test conditions:

• Hot idle test
• 48 km/h (30 mph) test
• 88 km/h (55 mph) test

6.  Perform circuit testing related to the suspected system issue:

• Input circuit testing
  a. KOEO input test for PCM sensors
  b. KOER input test for PCM sensors
  c. KOEO water soak test for PCM sensors (excluding high-voltage circuits)
  d. KOER water soak test for PCM sensors (excluding high-voltage circuits) 
  
• Output circuit testing:
  a. KOER wiggle test for PCM sensors
  b. KOER output test for PCM actuators
  c. KOEO water soak test for PCM actuators (excluding high-voltage circuits)
  d. KOER water soak test for PCM actuators
  

7. Inspect for any intermittent mechanical concerns.

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