2013 Harley Softail Starts But Runs Irregularly or Misses

The title “2013 Harley Softail Starts But Runs Irregularly or Misses” refers to a mechanical issue commonly encountered in a 2013 Harley-Davidson Softail motorcycle. This problem indicates that the motorcycle’s engine activates successfully, but it operates unevenly or experiences intermittent misfires during operation. Symptoms may include rough idling, fluctuating RPMs, hesitation or stumbling during acceleration, and an overall inconsistent engine performance. Such irregularities can stem from various factors such as fuel delivery problems, ignition system issues, air intake concerns, or faulty sensors, all of which can lead to an uneven combustion process. Addressing this issue may require diagnostic troubleshooting and repairs to restore the motorcycle’s smooth and reliable functioning.

Applicable Models

The troubleshooting guide provided here is designed to match each model’s year. It applies directly to the motorcycles listed below:

  • 2013 Harley-Davidson FXSB Breakout
  • 2013 Harley-Davidson FXST Softail Standard
  • 2013 Harley-Davidson FLSTC Heritage Softail Classic (including Anniversary)
  • 2013 Harley-Davidson FLSTF Fat Boy
  • 2013 Harley-Davidson FLSTFB Fat Boy Lo
  • 2013 Harley-Davidson FLSTFB Fat Boy Special (UK only)
  • 2013 Harley-Davidson FLSTN Softail Deluxe
  • 2013 Harley-Davidson FLS Slim
  • 2013 Harley-Davidson FXS Blackline
  • 2013 Harley-Davidson CVO Breakout

Starts But Runs Irregularly or Misses 

When your 2013 Harley Softail motorcycle starts but exhibits irregular running or misfires, it can be frustrating and concerning. Fortunately, this article delves into the various reasons behind this issue, offering insights and solutions to help you get your bike running smoothly again.

  1. Spark Plugs: Worn-out or partially fouled spark plugs can disrupt the combustion process, leading to uneven engine performance. Ensuring proper spark plug condition is essential for optimal ignition.
  2. Spark Plug Cables: Damaged spark plug cables can cause shorting or leaking of electrical energy, resulting in erratic engine operation. Checking and replacing these cables can make a significant difference.
  3. Spark Plug Gap: Incorrect spark plug gap, whether too narrow or too wide, can hinder proper ignition, leading to misfires. Verifying and adjusting the spark plug gap according to manufacturer specifications is crucial.
  4. Ignition Components: A faulty ignition coil, Engine Control Module (ECM), or sensor can interrupt the ignition sequence, causing irregular running. Thorough diagnostics of these components may be necessary.
  5. Battery Health: A nearly discharged battery can impact the overall electrical system, affecting ignition and fuel delivery. Ensuring a well-charged battery is essential for consistent engine performance.
  6. Electrical Connections: Damaged wires or loose connections at battery terminals, ignition coil, or ECM connector can disrupt electrical signals, leading to misfires. Regular inspection and maintenance of these connections are advised.
  7. Short Circuits: Intermittent short circuits resulting from damaged wire insulation can lead to inconsistent engine operation. Identifying and rectifying damaged wiring is essential for reliable performance.
  8. Fuel System Contaminants: Water or dirt in the fuel system can disrupt fuel delivery, causing misfires. Regular fuel system maintenance and using clean fuel are crucial preventive measures.
  9. Fuel Tank Vent System: A plugged fuel tank vent system can create a vacuum in the tank, affecting fuel flow and causing irregular running. Ensuring proper venting is necessary.
  10. Air Leaks: Leaks in the intake manifold or air cleaner can introduce excess air into the combustion process, leading to misfires. Detecting and sealing these leaks is vital.
  11. ECM Connection: Loose or dirty ECM connectors can result in faulty signal transmission, affecting engine performance. Keeping the ECM connections clean and secure is recommended.
  12. Sensor Issues: Malfunctioning sensors, such as the Manifold Absolute Pressure (MAP), Crank Position (CKP), or Oxygen (O2) sensors, can lead to incorrect fuel delivery and ignition timing. Diagnosing and replacing faulty sensors is essential.
  13. Valve Timing: Incorrect valve timing can disrupt the combustion process, causing irregular running. Ensuring precise valve timing through proper maintenance is crucial.
  14. Valve Springs: Weak or damaged valve springs can lead to valve float, affecting engine performance. Regular valve spring inspection is recommended.
  15. Valve Damage: Damaged intake or exhaust valves can lead to incomplete combustion and misfires. Inspection and potential replacement of damaged valves may be necessary.
  16. Fuel Injectors: Partially plugged fuel injectors can disrupt fuel delivery, leading to irregular running. Cleaning or replacing clogged injectors can restore proper fuel flow.
  17. Air Cleaner EVAP Solenoid: If equipped, a stuck-closed or inoperative air cleaner EVAP solenoid can affect air/fuel mixture, causing irregular running. Checking and maintaining this component is essential.

By carefully addressing these potential issues, you can effectively troubleshoot and rectify the irregular running or misfire problem in your 2013 Harley Softail motorcycle, ensuring a smoother and more enjoyable riding experience. Always refer to your motorcycle’s repair manual for specific guidance and consult with a certified Harley-Davidson mechanic when needed.


The information presented in this article is derived from the “2013 Softail Factory Service Manual,” specifically from Section 1.24 titled “General Troubleshooting,” found on page 85.

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