2018 Ford Explorer V6 3.5L – Backfires

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The 2018 Ford Explorer V6 3.5L has been reported to experience backfiring, a condition where unburned fuel ignites within the intake manifold or exhaust system. This issue may occur during acceleration, deceleration, or at idle, and can result in loud popping sounds, reduced engine performance, and potential damage to exhaust components. Common causes of backfiring include a misfiring ignition system, incorrect air-fuel mixture, a malfunctioning Exhaust Gas Recirculation (EGR) valve, or vacuum leaks in the intake system. Systematically troubleshooting and addressing these underlying issues can restore proper combustion, enhance engine efficiency, and prevent further damage to the vehicle's systems.

Procedure

A. Ignition System

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

2. Conduct a Power Balance Test using a Scan Tool.

• Expectation: The test passes.

3. Inspect the ignition system compartments for:

• All ignition coils are connected correctly and securely.
• Ignition coil boots for damage.
• Wiring harnesses and connectors for damage, burns, overheated insulation, and loose or broken conditions.
• The battery is in good condition and all of the accessories are turned OFF.

4. Turn the ignition ON and check the voltage between the Pin 3 of the Coil-On-Plug (COP) connector harness and ground.

• Expectation: greater than 10.5V.

5. If there are DTCs related to misfire, confirm the operation of the components for the misfiring cylinder, as follows:

• Remove the ignition coil, spark plug, and fuel injector related to the mifiring cylinder.
• Remove the ignition coil, spark plug, and fuel injector of the cylinder which is on the opposite bank of the misfiring cylinder.
• Swap the removed components between cylinders.
• Perform a test drive until the misfire occurs.
• Carry out the PCM self-test.

6. Check the spark presentation of the cylinder related to the retrieved DTC.

7. Check the spark presentation of all cylinders.

8. Check the resistance of the spark plugs.

• Expectation: in the 2,000 – 12,000 Ohms range at 25⁰C (77⁰F).

9. Check the resistance between the Pin 3 component side and the ignition coil spring located inside the ignition coil boot.

• Expectation: in the 5,000 – 6,000 Ohms range at 25⁰C (77⁰F).

B. Fuel Delivery System

1. Verify the Fuel System Integrity

Perform a visual inspection of all components in the fuel system, including:

• Fuel lines and connections
• Relays
• Fuel tank
• Fuel pump
• Fuel pressure regulator
• Fuel rail
• Connector pins for any signs of damage
• 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 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 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 the proper operation of the PCM.

C. Base Engine

Check for air leaks on the intake air system; or components and vacuum lines connected to the system (such as Positive Crankcase Ventilation (PCV), EGR valve).

D. 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 any 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

• Key ON Engine OFF (KOEO) input test for PCM sensors
• Key ON Engine Running (KOER) input test for PCM sensors
• KOEO water soak test for PCM sensors (excluding high-voltage circuits)
• KOER water soak test for PCM sensors (excluding high-voltage circuits)

Output circuit testing:

• KOER wiggle test for PCM sensors
• KOER output test for PCM actuators
• KOEO water soak test for PCM actuators (excluding high-voltage circuits)
• KOER water soak test for PCM actuators

7. Inspect for any intermittent mechanical concerns.

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