Why Are Your 2020 Ford Mustang Spark Plugs Fowling?

How to Fix Spark Plug Issues

This guide helps 2020 Ford Mustang owners troubleshoot and fix spark plug issues. Spark plug problems can lead to a variety of performance issues, from rough idling to reduced fuel efficiency. As one owner stated: "I mean they had it up in the air and pulled out the coils and spark plugs… not sure what other things they can do to diagnose this issue. I don’t know much about cars so I’d love to hear any solutions you may have." (source)

Symptoms

Owners experiencing spark plug issues with their vehicle have reported a few key symptoms. Keep an eye out for these warning signs.

One of the most noticeable symptoms is a clicking noise coming from the engine. This can indicate that the spark plugs are not firing correctly, or that there are issues in the ignition system. Identifying the source of the click can help you resolve the issue faster.

Spark plug fowling is another common symptom. This occurs when the spark plugs become coated with carbon, oil, or fuel, preventing them from firing properly. Fowling can lead to misfires, reduced power, and poor fuel economy.

Overheating is another symptom that can be linked to issues. This is often due to misfires placing unburned fuel into the exhaust system, which causes the catalytic converter to overheat.

A voltage drop can occur if the spark plugs are worn or damaged. This can affect the performance of other electrical components in the vehicle and may result in reduced power or stalling.

Most Likely Cause

Based on owner reports, the most likely cause of spark plug issues is related to the Mass Air Flow (MAF) sensor. A faulty MAF sensor can cause an improper air-fuel mixture, leading to spark plug fouling and misfires.

The MAF sensor measures the amount of air entering the engine. This information is crucial for the engine control unit (ECU) to calculate the correct amount of fuel to inject. If the MAF sensor is dirty or malfunctioning, it can send incorrect readings to the ECU, causing the engine to run too rich or too lean.

When the engine runs rich (too much fuel), the excess fuel can coat the spark plugs, leading to fowling. As one owner said: "Stock is best unless racecar/you are prepared to deal with the potential/realized problems from being non-stock. And with that, I agree on the MAF fouling." (source). Over time, this can significantly degrade their performance.

How to Diagnose

To diagnose spark plug issues potentially related to the MAF sensor on your vehicle, follow these steps:

1. Visual Inspection: Start by visually inspecting the spark plugs. Remove each spark plug and check for signs of fowling, such as carbon buildup, oil residue, or fuel deposits. Compare the condition of each spark plug to identify any that are significantly worse than the others.

2. MAF Sensor Inspection: Locate the MAF sensor, typically found in the intake air duct between the air filter and the throttle body. Inspect the sensor for any visible dirt or damage. Disconnect the electrical connector and check for corrosion or damaged pins.

3. MAF Sensor Cleaning: Use a specialized MAF sensor cleaner to clean the sensor. Do not use carburetor cleaner or other solvents, as they can damage the sensor. Spray the cleaner onto the sensor wires or filaments and allow it to air dry completely before reinstalling.

4. Check for Vacuum Leaks: Vacuum leaks can also cause the engine to run lean or rich, leading to spark plug issues. Inspect all vacuum hoses for cracks, leaks, or loose connections. Use a vacuum gauge to check the engine vacuum and identify any leaks.

5. Use an OBD-II Scanner: Connect an OBD-II scanner to the vehicle's diagnostic port to check for any trouble codes related to the MAF sensor, misfires, or fuel trim issues. Common codes include P0171 (System Too Lean, Bank 1), P0174 (System Too Lean, Bank 2), P0300 (Random Misfire Detected), and codes related to specific cylinder misfires (e.g., P0301, P0302).

6. Live Data Monitoring: Use the OBD-II scanner to monitor live data from the MAF sensor, oxygen sensors, and fuel trims. Check the MAF sensor readings at idle and under load to ensure they are within the specified range. Monitor the oxygen sensor readings to see if they are fluctuating properly, indicating a balanced air-fuel mixture.

Step-by-Step Fix

Follow these steps to address spark plug issues potentially linked to the MAF sensor:

1. Gather Tools and Parts: You'll need new spark plugs, a spark plug socket, a ratchet, an extension, a torque wrench, MAF sensor cleaner, and possibly a new MAF sensor (if cleaning doesn't resolve the issue). "Just buy a good torque wrench and get the right torque specs for your car. Max $50." (source)

2. Remove the Old Spark Plugs: Carefully remove the spark plug wires or coil packs from each spark plug. Use a spark plug socket and ratchet to loosen and remove the old spark plugs. Keep track of which spark plug came from which cylinder to help diagnose any specific cylinder issues.

3. Inspect the Spark Plugs: Examine the old spark plugs for signs of fouling, wear, or damage. Note the condition of each spark plug to help identify any underlying issues.

4. Clean or Replace the MAF Sensor: If the MAF sensor is dirty, spray it with MAF sensor cleaner and allow it to air dry completely. If the sensor is damaged or cleaning doesn't resolve the issue, replace it with a new MAF sensor.

5. Install the New Spark Plugs: Install the new spark plugs, making sure to gap them correctly according to the manufacturer's specifications. Use a torque wrench to tighten the spark plugs to the specified torque.

6. Reinstall the Spark Plug Wires or Coil Packs: Reconnect the spark plug wires or coil packs to the new spark plugs, making sure they are securely attached.

7. Clear Trouble Codes: Use an OBD-II scanner to clear any trouble codes that may have been triggered by the spark plug issues or MAF sensor problems.

8. Test Drive: Take the vehicle for a test drive to see if the spark plug issues have been resolved. Monitor the engine performance and check for any remaining symptoms, such as misfires or rough idling.

9. Monitor Fuel Trims: After completing the repair, use an OBD-II scanner to monitor the fuel trims. If the fuel trims are still outside the normal range, it may indicate that there are other underlying issues that need to be addressed, such as vacuum leaks or fuel system problems.

As one owner shared: "Unless you have need for that oiled filter setup, toss it directly in the trash. Find a stock one at a pull a part, they'll be like 20 bucks if that probably." ($20) (source) Consider replacing your air filter if it's an oiled aftermarket one to reduce MAF fouling.

Parts and Tools Needed

• New spark plugs (check your owner's manual for the correct type)
• Spark plug socket
• Ratchet
• Extension
• Torque wrench
• MAF sensor cleaner
• New MAF sensor (if needed)
• OBD-II scanner

Real Owner Costs

The cost of addressing spark plug issues can vary depending on whether you choose to do it yourself or take it to a mechanic. Here are some real-world cost examples:

• DIY Spark Plug Replacement: A set of spark plugs can cost between $20 and $100, depending on the type and brand. A spark plug socket and torque wrench can be purchased for around $50. So the total cost for a DIY spark plug replacement can range from $70 to $150. "Max $15 from harbor freight. Max 1 hour and a half start to finish, to do it carefully." ($15) (source)

• Professional Spark Plug Replacement: A mechanic will typically charge between $150 and $300 for a spark plug replacement, including parts and labor. The labor cost can vary depending on the complexity of the job and the hourly rate of the mechanic.

• MAF Sensor Cleaning: A can of MAF sensor cleaner costs around $10 to $20. Cleaning the MAF sensor yourself is a relatively simple and inexpensive task.

• MAF Sensor Replacement: A new MAF sensor can cost between $50 and $200, depending on the brand and quality. Professional installation can add another $50 to $100 to the total cost.

Prevention

To prevent spark plug issues in your vehicle, consider these preventative measures:

• Regular Maintenance: Follow the manufacturer's recommended maintenance schedule for spark plug replacement. This will help ensure that the spark plugs are in good condition and functioning properly.

• Use Quality Fuel: Use high-quality fuel with the correct octane rating for your vehicle. As one owner pointed out: "Octane rating is important in turbo vehicles because they often run higher compression and are prone to "predetonation" (aka knock) where the fuel ignites before spark." (source This can help prevent spark plug fouling and other fuel-related issues.

• Air Filter Maintenance: Regularly inspect and replace the air filter to ensure that the engine is getting clean air. A dirty air filter can restrict airflow and cause the engine to run rich, leading to spark plug fouling.

• MAF Sensor Cleaning: Clean the MAF sensor periodically to remove any dirt or debris that may be affecting its performance.

What Owners Say

Real experiences from FORD owners:

Owner Experiences

"Stock is best unless racecar/you are prepared to deal with the potential/realized problems from being non-stock. And with that, I agree on the MAF fouling." — houtex727 (source)

"Funny thing my friend had one too modified one ran perfect except once where he had weird misfire but got sparks or injectors (can’t remember) replaced ran fine and it ran mostly on regular" — Open_Battle2280 (source)

"At this point the nice 13/14 GT 500’s prices will be pretty stable depending on the state of the economy. At this point S197 GT500’s are “toys” to most owners." — imissher4ever (source)

Real Repair Costs

"Unless you have need for that oiled filter setup, toss it directly in the trash. Find a stock one at a pull a part, they'll be like 20 bucks if that probably." — houtex727 (source)

"Just buy a good torque wrench and get the right torque specs for your car. Max $50." — jerryeight (source)

"Max $15 from harbor freight. Max 1 hour and a half start to finish, to do it carefully." — jerryeight (source)

FAQ

Q: How long does it take to fix spark plug issues?

A: Replacing spark plugs yourself can take anywhere from 1 to 3 hours, depending on your experience and the complexity of the job. Cleaning the MAF sensor typically takes less than 30 minutes.

Q: Can I drive with fowling spark plugs?

A: It's not recommended to drive with fowling spark plugs. The resulting misfires can cause damage to the catalytic converter and other engine components.

Q: Is this a common issue on the 2020 Ford Mustang?

A: Spark plug issues can occur on any vehicle, but they are more common in vehicles with high mileage or those that are not properly maintained. Issues with the MAF sensor can exacerbate spark plug problems.

Q: DIY vs mechanic - what's recommended?

A: If you have experience working on cars, replacing spark plugs and cleaning the MAF sensor can be a relatively straightforward DIY job. However, if you're not comfortable working on your car or if the spark plug issues are severe, it's best to take it to a qualified mechanic.