How to troubleshoot engine misfires on a 1968 Ford Mustang GT Fastback (Bullitt)?

A common issue that might arise when owning a classic car like the 1968 Ford Mustang GT Fastback (Bullitt) is engine misfire. An engine misfire can be identified by symptoms such as rough idling, hesitation during acceleration, a sudden decrease in fuel efficiency, or in extreme cases, the engine stalling. This problem can be caused by a range of issues, from a fouled spark plug to ignition system failures. To help you figure out why your Mustang’s engine is misfiring, here is how to solve this issue:

Step 1: Inspect the Spark Plugs
Spark plugs are one of the most common culprits of engine misfires.

• Locate the Spark Plugs: In the engine bay, the spark plugs are usually found along the sides of the engine block. There will be 8 plugs if it's a V8 engine.
• Visual Identification: They are small, cylindrical components connected to thick, usually black or red wires.
• Check for Wear or Damage: Remove the spark plugs using a ratchet and spark plug socket. Look for signs of wear, fouling, or damage on the electrodes. If they are covered in carbon or oil deposits, it's time to replace them.

Step 2: Inspect the Ignition Wires
Faulty ignition wires can also cause misfires.

• Locate the Ignition Wires: These wires are connected directly to the top of the spark plugs and lead back to the distributor cap.
• Visual Identification: They are thick insulated wires, usually black or red.
• Check for Damage: Inspect the wires for cracks, burns, or any other signs of damage. If damaged, replace them with new ignition wires.

Step 3: Inspect the Distributor Cap and Rotor
The distributor cap and rotor are vital for proper engine ignition.

• Locate the Distributor Cap: Typically found at the rear or side of the engine, the distributor cap is a round plastic component, often connected to the ignition wires.
• Visual Identification: It’s usually black or brown and has multiple connectors for the ignition wires.
• Check for Wear: Remove the cap and inspect the rotor inside. Look for signs of wear, corrosion, or carbon buildup. If you notice any, replace both the distributor cap and rotor.

Step 4: Check the Fuel System
Issues with the fuel system can also cause misfires.

• Fuel Filter: Locate the fuel filter, which is typically along the fuel line under the car or near the fuel tank. It's a small, usually cylindrical component.
• Check for Clogs: If the fuel filter is clogged, fuel flow to the engine is restricted. Replace the filter if it's clogged or dirty.
• Fuel Injectors: These are located on the intake manifold and can be recognized as small nozzles with electrical connectors.
• Inspect for Clogs or Dirt: Over time, fuel injectors can become clogged. If dirty, clean them using a fuel injector cleaner or have them professionally cleaned.

Step 5: Check Engine Compression
Low engine compression can cause misfires.

• Locate the Spark Plug Holes: The compression test will involve using the spark plug holes.
• Visual Identification: They're where you removed the spark plugs from.
• Perform a Compression Test: Use a compression gauge. Insert it into each spark plug hole and crank the engine. Compare the readings to default specifications.
• Low Compression Solutions: If you detect low compression, it might indicate a problem with the pistons, valves, or cylinder walls, which would require more extensive engine repairs.

Conclusion
By systematically checking these components, you can identify and rectify the cause of engine misfires on your 1968 Ford Mustang GT Fastback (Bullitt). Always consult your vehicle's service manual for specific details and torque specifications. If you find yourself uncertain or unable to deal with the problem, it’s prudent to consult with a professional mechanic, particularly for complex issues like engine compression.