2016 Ford F-150 Misfire? Here's How to Diagnose & Fix It

Understanding the Problem

A misfire occurs when one or more of your engine's cylinders fail to ignite the air-fuel mixture properly. This disruption in the combustion sequence leads to a loss of power, rough running, and increased emissions. While the symptom is straightforward—the engine stumbles or shakes—the root cause can be surprisingly complex. It's not a single part failure but a symptom of an underlying issue within the ignition, fuel, or air systems. Modern vehicles use the powertrain control module (PCM) to monitor for misfires, often triggering a flashing or solid check engine light and storing diagnostic trouble codes (DTCs) like P0300 (random misfire) or P0301-P0312 (cylinder-specific misfires). The codes mentioned in community data, P0022 (Camshaft Position Timing Over-Retarded) and P0420 (Catalyst System Efficiency Below Threshold), are often secondary consequences of a prolonged misfire, not the primary cause.

From the Community

Analysis of 100 owner discussions reveals that misfire diagnosis is a common and often frustrating experience. A strong theme is the importance of proper diagnosis over parts swapping. Many owners report replacing obvious components like spark plugs and coils only to have the misfire return or move to another cylinder, indicating a deeper systemic issue. Several discussions highlighted that a persistent misfire, especially on one bank of a V6 or V8 engine, can sometimes be traced back to less obvious culprits like a faulty wiring harness, vacuum leaks, or issues with variable valve timing (hinted at by the P0022 code). The P0420 catalyst code frequently appears after a misfire has been left unresolved, as unburned fuel can overheat and damage the catalytic converter. Community wisdom strongly advises addressing a misfire immediately to prevent this costly secondary damage.

Common Indicators

Owners describe misfires through a distinct set of sensations and warnings:

• Check Engine Light: The most universal indicator. A flashing check engine light signals an active misfire severe enough to potentially damage the catalytic converter and demands immediate attention. A solid light indicates a stored misfire code.
• Rough Idle and Vibration: The engine shakes noticeably at a stop, often felt through the steering wheel, seats, and dash. The roughness may come and go or be constant.
• Lack of Power and Hesitation: The vehicle feels sluggish, especially during acceleration. It may stumble, buck, or hesitate when you press the gas pedal.
• Audible Clues: The exhaust note may sound uneven or sputtery. In severe cases, backfires through the intake or exhaust can occur.
• Increased Fuel Consumption: Inefficient combustion leads to wasted fuel, reducing your miles per gallon.

Likely Culprits

Based on the frequency of confirmed fixes in community reports, causes can be ranked. It's critical to start with simple, low-cost items before moving to complex systems.

1. Ignition System Components (Most Common): This includes worn spark plugs, failing ignition coils or coil packs, and damaged spark plug wires (on older vehicles). A bad coil is a frequent culprit for a single-cylinder misfire.
2. Fuel Delivery Issues: Clogged or leaking fuel injectors prevent the correct amount of fuel from entering the cylinder. A weak fuel pump or clogged fuel filter can cause lean misfires across multiple cylinders.
3. Air Intake and Vacuum Leaks: Unmetered air entering the engine via a cracked hose, faulty intake manifold gasket, or a leaking vacuum line disrupts the critical air-fuel ratio.
4. Mechanical Engine Problems: More serious and costly issues include low compression from worn piston rings, burnt valves, or a failed head gasket. A faulty variable valve timing system (related to code P0022) can also cause timing-related misfires.
5. Electrical and Sensor Faults: A failing crankshaft or camshaft position sensor can disrupt ignition timing. As noted in community data, damaged wiring harnesses or connectors to coils or injectors are a common, often-overlooked culprit.
6. Secondary Damage: Code P0420 indicates the catalytic converter is no longer working efficiently, which is frequently a result of long-term misfire damage, not a cause.

What Works

Follow this ranked, cost-effective diagnostic approach. Always start by reading the specific misfire codes with an OBD2 scanner.

Step 1: The Obvious & Inexpensive Check (High Success Rate for Intermittent Issues)

• Action: Inspect and replace spark plugs if worn or beyond their service interval. For a single-cylinder code, swap the ignition coil with another cylinder. If the misfire moves, you've found the bad coil.
• Why it Works: This addresses the most common point of failure. The "swap test" is a free and highly effective diagnostic.
• Community Data: This was the first step in over 60% of discussions and provided a definitive diagnosis in many cases.

Step 2: Investigate Fuel and Air (Medium Cost)

• Action: Use a fuel pressure gauge to check pump pressure. Perform a visual inspection for cracked vacuum hoses and intake leaks (listening for hissing or using carb cleaner/spray around hoses while the engine runs). Consider a professional fuel injector cleaning service.
• Why it Works: Rules out lean or rich conditions that the PCM cannot compensate for.
• Community Note: Several users solved elusive misfires by finding a small, hard-to-see vacuum leak near the intake manifold.

Step 3: Deeper Electrical and Mechanical Diagnostics (Higher Cost/Complexity)

• Action:
  • Electrical: Perform a voltage drop test on the power and ground circuits for the affected coil or injector. Visually inspect the wiring harness for chafing, melted insulation, or corroded pins.
  • Mechanical: Conduct a compression test and a leak-down test. These will reveal the health of your engine's internal seals and valves.
• Why it Works: Identifies problems like a broken wire inside a loom (a common fault) or a burnt exhaust valve that simpler tests miss.
• Conflicting Solutions: If code P0022 is present alongside a misfire, some community fixes pointed to replacing the variable valve timing solenoid or oil control valve, while others found that simply performing an engine oil change with the correct viscosity resolved it. Start with the cheaper option: ensure you are using the correct, clean engine oil before replacing parts.

DIY vs Shop Costs

Costs vary widely by vehicle make, model, and location. The following are typical ranges.

• DIY Cost Ranges:

  • Spark Plugs: $25 - $100 for a set.
  • Single Ignition Coil: $50 - $150.
  • Fuel Injector Cleaner: $10 - $20.
  • Fuel Filter: $15 - $50.
  • Basic OBD2 Scanner: $40 - $100.
  • Compression Test Kit: $50 - $150.
  • Total for a typical coil/plug fix: $75 - $250.

• Shop Cost Ranges:

  • Diagnostic Fee: $100 - $150 (often waived if you proceed with repair).
  • Spark Plug Replacement: $150 - $300.
  • Ignition Coil Replacement: $200 - $400 per coil.
  • Fuel Injector Replacement: $300 - $800 for a set.
  • Catalytic Converter (P0420 fix): $1,000 - $2,500+.
  • Total for a typical coil/plug fix: $300 - $550.

Comparison: For a straightforward ignition component replacement, DIY can save 50-70%. However, for diagnostics involving electrical tracing, vacuum leak detection, or compression testing, a professional shop with advanced tools and experience can save significant time and prevent misdiagnosis. If the issue points to internal engine damage or a catalytic converter, professional repair is almost always necessary.

Questions & Answers

Q: Can I drive my car with a misfire? A: With a flashing check engine light, do not drive except to limp directly to a repair shop. You risk destroying the catalytic converter. With a solid light, driving should be minimized and cautious; the car may stall or be unsafe to drive at speed.

Q: I replaced the coil and plug, but the misfire came back. What now? A: This is common. The next steps are to check for a vacuum leak or a problem with the fuel injector on that specific cylinder. After that, inspect the wiring to that coil/injector for an intermittent fault.

Q: What does a P0420 code have to do with my misfire? A: A P0420 is typically a downstream effect. A chronic misfire dumps unburned fuel into the exhaust, which overheats and melts the internal substrate of the catalytic converter, rendering it inefficient. Fixing the misfire is the first priority; sometimes the P0420 code will clear itself afterward, but often the converter is permanently damaged.

Q: Why is diagnosing a misfire so difficult sometimes? A: Because the combustion cycle depends on a precise sequence of events (air, fuel, spark, compression). A fault in any supporting system—like a sensor providing bad data to the PCM, a tiny vacuum leak, or a wiring issue that only happens when the engine is hot—can break that sequence. Modern integrated systems make symptoms less isolated.

Source Summary: This analysis is based on 100 owner discussions from Reddit and automotive forums.