Fixing Misfire Issues: 2012 Mustang GT Coil Pack Swap
The video shows diagnosing and fixing a cylinder misfire on a 2012 Mustang GT by swapping/replacing the coil pack(s). The process includes scanning for misfire codes, removing the coil-on-plug assembly, swapping or installing a new coil, clearing codes, and verifying the fix with another scan or a test drive.
Build Sequence
1. Scan for trouble codes
Connect an OBD-II scanner to read active and pending diagnostic trouble codes to identify which cylinder(s) are misfiring (P030x). Note the specific cylinder numbers before beginning repairs.
2. Prepare vehicle and access coils
Park on a level surface, allow the engine to cool, disconnect the negative battery terminal if desired for safety, and remove any engine covers or components blocking access to the coil-on-plug assemblies.
3. Unplug the coil electrical connector
Locate the coil for the affected cylinder and carefully depress the locking tab on the electrical connector, then pull the connector free to avoid damaging the wiring tab.
4. Remove coil mounting bolt(s) and extract coil
Using the appropriate socket and extension, remove the bolt(s) securing the coil pack, then pull the coil straight up out of the spark plug well. Inspect the coil boot and wiring for damage or corrosion.
5. Diagnose/confirm by swapping coils (optional)
If unsure the coil is bad, swap the suspect coil with a coil from a known-good cylinder and re-scan. If the misfire code follows the coil, the coil is faulty.
6. Install replacement coil / re-seat components
Apply a small amount of dielectric grease to the inside of the coil boot (if recommended), seat the new coil onto the spark plug, reinstall the mounting bolt and torque to manufacturer spec, and reconnect the electrical connector.
7. Clear codes and verify repair
Clear stored codes with the scanner, start the engine and verify the misfire is gone. Check live data for misfire counts and take a short test drive to confirm proper running.
8. Inspect related components
If misfire persists, inspect spark plugs, wiring harness, and fuel injectors for issues and repeat diagnostics as needed; consider replacing spark plugs if worn.
Frequently Asked Questions
How do I know which coil is bad?
Read the OBD-II codes (P030x) to identify the misfiring cylinder. You can also swap the suspect coil with a known-good cylinder — if the misfire moves to the other cylinder, the coil is the culprit.
VIEW FULL ARTICLE →Do I need to replace the spark plug when replacing a coil?
Not always, but it's a good idea to inspect the spark plug. If the plug is worn, fouled, or has high mileage, replace it while you have the coil off. New coils on old plugs can mask underlying plug problems.
VIEW FULL ARTICLE →Can I clear the code and drive without replacing the coil?
You can clear the code, but if the coil is failing the misfire will likely return and could damage the catalytic converter if left unaddressed. Replace the faulty coil to prevent further issues.
VIEW FULL ARTICLE →What torque should I use for the coil mounting bolt?
Always follow the factory torque specification when available. If you don't have the spec, snug the bolt without over-torquing — typically a low torque value (single-digit ft-lb or around 7–10 Nm) is used for coil bolts.
VIEW FULL ARTICLE →Related Builds
Parts Used (3)
Used to replace the faulty cylinder coil; 2011-2014 Mustang GT uses individual coils for each cylinder (Coyote V8). Price is approximate for an OEM-quality coil.
Often recommended to inspect or replace spark plugs when servicing coils; estimate per plug. Replace if worn or if vehicle has high miles.