P0305 on 2017 Ford Fusion Sport: 2.7L V6 Cylinder 5 Misfire Causes and Fixes

What's Unique About the 2017-2017 Ford FUSION

The 2017 Fusion Sport uses a high-performance 2.7L EcoBoost V6 engine. While standard misfire causes like spark plugs and coils are common, this specific engine platform is subject to serious manufacturer-issued Technical Service Bulletins (TSBs). These bulletins highlight a known issue where excessive oil consumption, caused by problems with cylinder head valve guides, can lead to misfires and potentially catastrophic engine damage. This makes it critical to investigate oil levels and consumption when diagnosing a P0305 code on this vehicle, as simply replacing a spark plug will not fix the root cause.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check engine light is on or flashing
• Rough or shaky idle
• Engine hesitation or stumbling during acceleration
• Noticeable loss of power
• Reduced fuel economy
• Smell of fuel from the exhaust
• Blue or white smoke from the exhaust, especially after a hot restart

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability → Shop Ignition Coil Coil-on-plug systems are a common failure point due to heat and vibration. Over time, the internal windings can break down, leading to a weak or non-existent spark.
   How to confirm: Swap the ignition coil from cylinder 5 with another cylinder (e.g., cylinder 4). Clear the codes and drive the vehicle. If the code changes to P0304, the ignition coil is bad. This is a definitive DIY diagnostic step.
   Typical fix: Replace the faulty ignition coil. It is often recommended to replace the corresponding spark plug at the same time. Applying a small amount of dielectric grease to the new coil boot is best practice.
   Est. part cost: $40-$90
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug Given the TSBs for oil consumption, spark plugs on this engine can become fouled with oil, leading to misfires. EcoBoost engines are also generally sensitive to spark plug wear and correct gapping due to the stresses of turbocharging and direct injection.
   How to confirm: Remove and inspect the spark plug from cylinder 5. Look for signs of wear, carbon buildup, or oil fouling. A cracked porcelain insulator, sometimes visible as a thin black line, is a common failure mode. Compare it to a plug from a non-misfiring cylinder.
   Typical fix: Replace the spark plug. The recommended gap for the 2.7L EcoBoost is 0.028-0.031 inches. If oil fouling is present, the root cause of the oil consumption must be addressed. It is best practice to replace all six spark plugs at once. 🎬 See this step-by-step guide for replacing EcoBoost spark plugs
   Est. part cost: $10-$25 per plug
3. Internal Engine Issues (per TSBs) 🟡 Medium Probability TSBs 19-2243 and others specifically call out that P030x codes on 2017 Fusions with the 2.7L engine (built between April 2016 and Jan 2017) can be caused by excessive oil consumption due to faulty cylinder head valve guides.
   How to confirm: Monitor oil consumption closely; consumption of more than one quart in 3,000 miles is a key indicator. Perform a cylinder compression test and a leak-down test to check for mechanical engine health. The presence of blue or white exhaust smoke, especially after a hot restart, 🎬 Watch: Understanding the fix for blue smoke on startup is another strong symptom.
   Typical fix: This is a major repair. Per the TSBs, the fix is to replace the cylinder heads. In some cases where codes P0524/P06DD are also present, the entire engine long block may need replacement.
   Est. part cost: $2000+
4. Clogged or Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector Direct injection (DI) fuel injectors can be susceptible to carbon buildup over time, which can disrupt the spray pattern and cause a misfire.
   How to confirm: A professional can perform a fuel injector balance test. A DIY method is to listen to the injector with a mechanic's stethoscope to ensure it is clicking. Swapping injectors between cylinders is possible but more involved than swapping coils.
   Typical fix: Clean or replace the fuel injector for cylinder 5.
   Est. part cost: $70-$150

Rare But Worth Checking

• Vacuum Leak: A vacuum leak near the intake manifold for cylinder 5 could lean out the air-fuel mixture and cause a misfire. This is less common for a single-cylinder misfire.
• Powertrain Control Module (PCM) Fault: This is extremely rare, and all other possibilities should be exhausted before considering the PCM as the cause. Sometimes a failed ignition coil can damage the PCM driver circuit, but this is more common on older Ford models.

Diagnosis Steps

1. Read the code with an OBD-II scanner and note any other codes present. Freeze frame data can provide clues about the engine's condition when the misfire occurred.
2. Check the engine oil level and condition. If it is low, top it off and monitor for excessive consumption (more than 1 quart per 3,000 miles).
3. Locate cylinder 5. On the 🎬 Watch: How to identify cylinder locations on the 2.7L engine transverse 2.7L V6 in the Fusion, the passenger side bank (Bank 1) is 1-2-3 (front to back) and the driver's side bank (Bank 2) is 4-5-6 (front to back). Cylinder 5 is the middle cylinder on the driver's side bank.
4. Swap the ignition coil from cylinder 5 to an adjacent cylinder (like cylinder 4 or 6). Clear the codes and run the engine to see if the misfire code follows the coil (e.g., changes to P0304 or P0306). If it does, the coil is bad.
5. If the misfire stays on cylinder 5, remove and inspect the spark plug. Look for excessive wear, damage, or fouling from oil or fuel. Check for cracks in the porcelain. Verify the gap is between 0.028-0.031 inches.
6. If the spark plug is good, the next step is to check the fuel injector. This may require professional assistance or swapping the injector to another cylinder.
7. If basic ignition and fuel components are ruled out, perform a cylinder compression test and leak-down test to check for mechanical engine problems. Low compression can confirm an internal issue like worn piston rings or the valve guide problem noted in TSBs.

Parts You'll Likely Need

• Ignition Coil (OEM #DG-549) — A common failure point for ignition systems causing a single-cylinder misfire.
  Trusted brands: Motorcraft, NGK, Denso
  OEM price range: $60-$90
  Aftermarket price range: $40-$70
• Spark Plug (OEM #SP-578 (replaces SP-542)) — A regular maintenance item that wears out. Can also become fouled by oil due to known engine issues, causing a misfire.
  Trusted brands: Motorcraft, NGK
  OEM price range: $15-$25
  Aftermarket price range: $10-$20

Related Codes That Often Appear With This One

• P0300 — Indicates a random or multiple cylinder misfire, which can occur if the underlying problem (like the TSB-related oil consumption) starts to affect other cylinders.
• P0301, P0302, P0303, P0304, P0306 — Misfire codes for other cylinders. Seeing multiple codes often points towards a systemic issue like the oil consumption problem or a clogged catalytic converter.
• P0316 — Indicates a misfire was detected within the first 1000 engine revolutions on startup, which is common with these issues and is explicitly mentioned in the TSBs.
• P0524 — Stands for 'Engine Oil Pressure Too Low'. Its presence alongside a misfire code strongly points to the serious internal engine issues described in Ford's TSBs.
• P06DD — Stands for 'Engine Oil Pressure Control Solenoid Stuck Off'. Like P0524, this code reinforces the likelihood of a severe oiling system or internal engine problem as noted in the TSBs.

Technical Service Bulletins (TSBs) & Recalls

• SSM 54504: Notes that P030x misfire codes can be linked to excessive oil consumption on 2017 Fusions with the 2.7L/3.0L engine.
• SSM 46364: Suggests cylinder heads or the long block may be the root cause of P030x misfires, especially when accompanied by excessive oil consumption or codes P0524/P06DD.
• TSB 19-2243: Supersedes earlier TSBs (like 17-2235), providing updated procedures for replacing the cylinder heads on 2017 Fusions with the 2.7L engine (built 1-Apr-2016 through 1-Jan-2017) exhibiting oil consumption and misfires due to valve guide issues.

Platform-Specific Known Issues

• Excessive Oil Consumption: The 2017 Fusion Sport's 2.7L EcoBoost engine is explicitly mentioned in Ford TSB 19-2243 for a defect that can cause excessive oil consumption (over 1 quart per 3,000 miles). This issue is often the root cause of misfire codes, rough idle, and blue/white exhaust smoke. The prescribed fix is a major repair, involving cylinder head replacement due to faulty valve guides.

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance — expected: 0.4 to 2.0 ohms. Failure: A reading outside this range indicates a faulty primary winding.
• Ignition Coil Secondary Resistance — expected: 6,000 to 10,000 ohms (6kΩ - 10kΩ). Failure: A reading outside this range, or an open circuit (infinite resistance), points to a failure in the secondary windings.
• Low-Side Fuel Pressure (at idle) — expected: 35 to 65 PSI. Failure: Pressure significantly below this range indicates a weak in-tank fuel pump or supply issue.
• High-Side Fuel Pressure (engine running) — expected: 500 to 2,500+ PSI (varies with engine load). Failure: Pressure that fails to meet the PCM's desired pressure reading (viewable on a scan tool) indicates a problem with the high-pressure fuel pump (HPFP) or its sensor.

Hidden / Shadow Codes Worth Checking

• Mode 6, Test ID $A2-$A7: Ford uses Mode 6 data to store misfire counts for each cylinder over the current and last 10 driving cycles. A technician can view this data with a capable scan tool to see which cylinder is misfiring, even if the misfire count isn't high enough to set a P030x trouble code. For a V6, Test IDs $A2 through $A7 correspond to cylinders 1 through 6. A non-zero value for Test ID $A6 (Cylinder 5) indicates misfire events have occurred. (see via A professional scan tool or advanced DIY tool (like FORScan) with Mode 6 capabilities.)

Scan Tool Commands That Help

• Ford IDS, FORScan, or equivalent professional scanner: Power Balance Test — This function graphically displays the power contribution of each cylinder while the engine is running. It allows a technician to visually identify that cylinder 5 is contributing less power than the others, confirming the misfire in real-time and helping to rule out sensor glitches.
• Ford IDS, FORScan, or equivalent professional scanner: Misfire Monitor Neutral Profile Correction — This is a relearn procedure that MUST be performed after replacing the PCM, crankshaft position sensor, or after major internal engine work (timing components, flywheel, etc.). Failure to perform this relearn can cause the PCM to incorrectly interpret crankshaft speed variations, leading to false misfire codes like P0305.

Wiring & Ground Locations

• Engine Ground Point — On some Fusion models, a dedicated ground post is located on the top of the strut mount tower in the engine bay.. This provides a clean, reliable chassis ground point for performing electrical tests with a multimeter, such as checking for voltage drop or continuity on the ignition coil or fuel injector circuits.
• Engine to Body Ground Strap — Typically a thick, braided copper wire connecting the engine block or transmission housing directly to the vehicle's chassis/firewall.. A corroded or loose main engine ground strap can cause a wide range of electrical issues, including weak spark or erratic sensor readings, which can lead to misfires. Ensuring this connection is clean and tight is a fundamental step in diagnosing any electrical fault.

Real Owner Repair Stories

• Reddit user, r/MechanicAdvice (2018 Ford F-150 with 2.7L EcoBoost) — Persistent P0305 misfire only at idle, good power throughout the rev range, long crank startups.
  ❌ Tried (didn't work) Replaced all port and direct fuel injectors.
  ✅ What actually fixed it The issue was not resolved by the owner. A Ford dealer performed a manual compression and leak-down test and diagnosed a burnt exhaust valve in cylinder 5, quoting $19,000 for a new engine. The owner sold the vehicle. This highlights a potential for severe mechanical failure even when symptoms seem minor.
• Reddit user report cited by Go-Parts.com (2017 Ford Fusion Sport (2.7L EcoBoost) with 18,000 miles) — Rough idle, engine hesitation on acceleration, codes P0300 (Random Misfire) and P0316 (Misfire on Startup).
  ❌ Tried (didn't work) Initial suspicion was a major internal engine issue.
  ✅ What actually fixed it The Ford dealer diagnosed and replaced a faulty (plugged up) EVAP purge valve. This is a critical misdiagnosis case, as the misfire was caused by an emissions component creating a vacuum leak, not an ignition or fuel system fault.

"I Checked Everything" — The Actual Cause

• A common diagnostic step for misfires is a smoke test to find vacuum leaks. However, a faulty EVAP purge valve can cause a lean condition and misfires without being detected by a smoke test. The valve, when stuck open, introduces unmetered fuel vapor into the intake manifold, mimicking a vacuum leak, but since it is a sealed system, a smoke test may show no leaks. A 2017 Fusion Sport with misfire codes was fixed by replacing a plugged EVAP purge valve after initially suspecting a major engine problem.

When the Usual Fixes Don't Work

• While P0305 is most commonly a simple ignition coil or spark plug issue, it should not be treated lightly on this platform. A real-world case on a 2.7L EcoBoost with a persistent P0305 that only occurred at idle was ultimately diagnosed by a dealer as a burnt exhaust valve, requiring engine replacement. This demonstrates that even with minor symptoms, the root cause can be a severe mechanical failure that a simple tune-up will not fix. Furthermore, misfire codes on this engine can be caused by seemingly unrelated components; another documented case on a 2017 Fusion Sport was resolved by replacing a faulty EVAP purge valve that was creating a lean condition. This proves that diagnosis should not be limited only to the ignition and fuel components of cylinder 5.

OEM Part Supersession History

• SP-542 → SP-578 — Ford often updates spark plug designs for improved performance, durability, or to address issues seen in the field. The change to SP-578 was part of this evolution.
• SP-578 → SP-594 — Further refinement of the spark plug design for the 2.7L EcoBoost platform.
  Heads up: While SP-578 will work, SP-594 is the latest recommended OEM part for this engine. Using the most current part number is best practice.

Model Year Variations Within This Range

• 2017: The TSBs regarding excessive oil consumption and subsequent misfires due to cylinder head valve guide issues specifically apply to 2017 Ford Fusions with the 2.7L engine built from April 1, 2016, through January 1, 2017. Vehicles built outside this range are less likely to experience this specific defect.