P0305 on 2017 Lincoln MKZ: Cylinder 5 Misfire Causes and Fixes

What's Unique About the 2017-2017 Lincoln MKZ

For the 2017 Lincoln MKZ equipped with a 3.0L V6 engine, a P0305 code can be more than just a simple ignition problem. Lincoln has issued Technical Service Bulletins (TSBs), notably SSM 54504 and SSM 46364, indicating that misfire codes can be a direct symptom of excessive oil consumption. This condition may point to significant internal engine problems, such as issues with the cylinder heads or even the entire long block, which is a much more severe and costly issue than a typical spark plug or coil failure.

Diagnostic Flowchart

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

Symptoms You May Notice

• Flashing or solid Check Engine Light
• Rough or vibrating idle.
• Engine hesitation or stumbling during acceleration.
• Noticeable loss of engine power.
• Reduced fuel economy.
• Difficulty starting the engine
• White or blue smoke from the exhaust, especially after a hot restart (per TSBs).

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability → Shop Ignition Coil Coil-on-plug systems are a common failure point on many modern engines. Heat and vibration cause the internal windings to fail over time.
   How to confirm: Swap the ignition coil from cylinder 5 with another cylinder on the same bank (e.g., cylinder 4 or 6). Cylinder 5 is on the front bank (near the radiator). If the code changes to P0304 or P0306, the coil is the faulty part.
   Typical fix: Replace the failed ignition coil. It is often recommended to replace all three coils on the front bank at the same time. Since access is relatively easy, replacing just the single failed coil is also a common repair.
   Est. part cost: $40-$90 per coil
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug
   How to confirm: Remove the spark plug from cylinder 5 and inspect it. Look for a worn electrode, heavy carbon buildup, or oil/fuel fouling. An oil-fouled plug is a strong indicator of the internal engine issues described in the TSBs.
   Typical fix: Replace the spark plug. It is best practice to replace all six spark plugs 🎬 See this walkthrough for replacing MKZ spark plugs and coils. at the same time to ensure even performance. Use the OEM-specified Iridium plugs for best results.
   Est. part cost: $15-$30 per plug
3. Internal Engine Issues (per TSBs) 🟡 Medium Probability TSBs SSM 54504 and SSM 46364 specifically state that for 2017 MKZ models with the 3.0L engine, misfire codes can be caused by excessive oil consumption (1 quart in <3,000 miles). A related TSB for the similar 2.7L engine, 19-2384, identifies the cause as faulty cylinder head valve guides. 🎬 Watch: How faulty valve guides cause blue smoke on startup.
   How to confirm: Monitor oil levels closely. If the engine consumes more than 1 quart in 3,000 miles, this is a likely cause. A cylinder compression test and leak-down test are necessary for a definitive diagnosis. The presence of codes P0524 (Engine Oil Pressure Too Low) or P06DD (Engine Oil Pressure Control Circuit Stuck Off) strongly points to this issue.
   Typical fix: This is a major repair. Per TSB SSM 46364, the fix may be to replace the cylinder heads. If oil pressure codes are also present, the TSB suggests the long block may be the cause. A related TSB for a similar engine (19-2384) details the cylinder head replacement procedure.
   Est. part cost: $2500-$8000+
4. Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector
   How to confirm: A professional can perform a fuel injector balance test. A DIY method is to listen for a consistent clicking sound from the injector with a mechanic's stethoscope. Swapping injectors is possible but more involved than swapping coils.
   Typical fix: Replace the faulty fuel injector.
   Est. part cost: $70-$150
5. PCM Reprogramming Needed ⚪ Low Probability TSB #16-0113 notes that some vehicles may exhibit rough idle and misfire codes due to PCM calibration.
   How to confirm: A Ford/Lincoln dealership or a qualified shop with an IDS scan tool can check the current PCM calibration level against the latest available version.
   Typical fix: Reprogram the Powertrain Control Module (PCM) to the latest software version using IDS release 102.01 or higher.
   Est. part cost: $0 (if under warranty) - $150

Rare But Worth Checking

• Vacuum Leak: A vacuum leak near the intake manifold runner for cylinder 5 could lean out the air-fuel mixture and cause a misfire. This could be from a failed gasket or a cracked intake manifold.
• Low Cylinder Compression: While related to the TSBs, low compression can also be caused by other issues like a burnt valve or damaged piston rings, independent of the oil consumption problem.
• Failed PCM Ignition Driver: On some Ford platforms, the internal transistor in the PCM that controls the ignition coil for a specific cylinder can fail. This results in a persistent misfire on that cylinder even with a new coil and plug. This typically requires sending the PCM out for repair or replacing it.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner and note any other codes present.
2. Check for the presence of oil pressure codes (P0524, P06DD), which would elevate the seriousness of the issue per TSBs SSM 54504 and SSM 46364.
3. Identify Cylinder 5. 🎬 Watch: A breakdown of P0305 causes and common fixes. On the transverse V6 engines, it is on the front bank (near the radiator), the middle cylinder.
4. To test the ignition coil, swap the coil from cylinder 5 with cylinder 4 or 6. Clear the codes and drive the vehicle. If the code returns as P0304 or P0306, the ignition coil is faulty.
5. If the misfire remains on cylinder 5, remove and inspect the spark plug. Look for signs of wear, oil, or fuel fouling. An oil-fouled plug is a major red flag for the TSB-related engine issue.
6. If ignition components are good, inspect the fuel injector and its wiring for cylinder 5.
7. Check for any applicable TSBs. TSB #16-0113 suggests a PCM reprogram for rough idle, while TSBs SSM 54504 and SSM 46364 point to major engine work for misfires with oil consumption.
8. Begin monitoring engine oil consumption. If it is excessive (1 quart in <3,000 miles), the cause is very likely the cylinder head issue described in the TSBs.
9. If the cause is still not found, perform a cylinder compression test and a leak-down test to check for mechanical engine health.

Parts You'll Likely Need

• Ignition Coil (OEM #DG549 (Motorcraft)) — This is one of the most common failure items for a single-cylinder misfire.
  Trusted brands: Motorcraft, NGK, Denso
  OEM price range: $60-$100
  Aftermarket price range: $40-$90
• Spark Plug (OEM #SP-578 (Motorcraft, for 3.0L) or SP-534 / SP-580 (Motorcraft, for 3.7L)) — Spark plugs are a routine maintenance item and can become worn or fouled, causing a misfire.
  Trusted brands: Motorcraft, NGK, Bosch
  OEM price range: $15-$30
  Aftermarket price range: $10-$20
• Intake Manifold Gasket — Required when replacing the rear bank of spark plugs or ignition coils on the V6 engines. Not required for a P0305 fix alone, as cylinder 5 is on the front bank.
  Trusted brands: Motorcraft, Fel-Pro
  OEM price range: $30-$50
  Aftermarket price range: $20-$40

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or affects other cylinders, a P0300 (Random Misfire) code may appear alongside P0305.
• P0301, P0302, P0303, P0304, P0306 — Codes for other cylinders indicate a wider problem than just a single coil or plug, pointing towards issues like a vacuum leak, fuel delivery problems, or the engine-wide issues mentioned in the TSBs.
• P0524, P06DD — According to TSBs SSM 54504 and SSM 46364, these oil pressure codes appearing with misfire codes are a strong indicator of a severe internal engine problem requiring inspection of the cylinder heads or long block.

Technical Service Bulletins (TSBs) & Recalls

• SSM 54504: Excessive oil consumption with DTCs P0300-P0306, P0524, P06DD
• SSM 46364: Excessive oil consumption with DTCs P0300-P0306, suspect cylinder heads or long block
• TSB 16-0113: Rough idle with or without misfire DTCs, PCM reprogram
• TSB 19-2243: Supersedes previous TSBs, identifies faulty valve guides in cylinder heads as the cause for oil consumption and misfires on 2.7L/3.0L engines, prescribing cylinder head replacement.

Platform-Specific Known Issues

• TSB-Related Oil Consumption & Misfires (3.0L V6): TSBs SSM 54504 and SSM 46364 are critical for this engine. They explicitly link misfire codes (P0300-P0306) with excessive oil consumption (1 qt in <3000 miles), rough idle, and potentially oil pressure codes (P0524, P06DD). The cause points to internal engine issues with the cylinder heads or long block, requiring major professional repair. A similar issue on the 2.7L engine was traced to faulty cylinder head valve guides.
• TSB 16-0113: PCM Calibration for Rough Idle: For some 2017 MKZ models, a rough idle at normal operating temperature or after a hot restart, with or without misfire codes, may be due to the PCM software calibration. The fix is to reprogram the PCM to the latest version using a dealer-level IDS scan tool (release 102.01 or higher).

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance — expected: 0.4 - 2.0 ohms. Failure: A reading outside this range suggests a failing coil.
• Ignition Coil Secondary Resistance — expected: 8 - 12 kΩ (kilohms). Failure: A reading outside this range may indicate a faulty coil.
• High Pressure Fuel Rail Pressure (Direct Injection) — expected: Varies by load, can range from 943 psi at idle to over 3,700 psi under load.. Failure: Pressure that does not respond to engine load or is significantly lower than commanded pressure. A sensor voltage below 0.27V or above 4.76V indicates a sensor fault.
• Mode $06 Misfire Count (per cylinder) — expected: Counts should be at or very near zero for all cylinders.. Failure: A significantly higher misfire count on cylinder 5 compared to others, even without a P0305 code being set, indicates an intermittent or developing issue.

Hidden / Shadow Codes Worth Checking

• Mode $06, TID $53: This is not a DTC, but a Test ID within Mode $06 data that tracks misfire counts for each cylinder during specific monitoring periods (e.g., last 10 drive cycles). It allows a technician to see which cylinder is misfiring before the count is high enough to trigger a Check Engine Light. (see via A professional scan tool or an advanced OBD-II app capable of displaying Mode $06 data.)

Scan Tool Commands That Help

• Ford IDS (or compatible high-end scanner like Snap-on): Power Balance Test — This is a live data test that graphically displays the power contribution of each cylinder. A technician can use this to confirm a lack of contribution from cylinder 5 in real-time. The tool also allows for disabling individual injectors to see the effect on the engine, helping to isolate the fault.
• Ford IDS (or compatible, like FORScan): Misfire Monitor Neutral Profile Correction — This relearn procedure is mandatory after major engine or transmission repairs, including engine or cylinder head replacement. Failure to perform this can cause the PCM to incorrectly detect misfires because it has not learned the new mechanical variances of the crankshaft position sensor's reluctor wheel, potentially setting false P030x codes.

Wiring & Ground Locations

• G107 — Typically located on the chassis in the engine bay, near the A-pillar or on the radiator support.. This is a primary ground point for the engine and PCM. A poor, corroded, or loose connection here can cause erratic voltage and signal issues for the entire ignition system, leading to misfires that are difficult to diagnose.
• Ignition Coil Connector — Directly on top of the ignition coil for cylinder 5.. The connector or its pigtail wiring can become brittle from heat and vibration, causing a poor connection. Technicians will check for battery voltage on the power supply wire (Pin 2, often a pink wire on Fords) and check the control wire for continuity back to the PCM.

Real Owner Repair Stories

• Ford Edge Forum (Ford Edge with 2.7L EcoBoost (engine shared with MKZ)) — Check engine light with misfire codes.
  ❌ Tried (didn't work) Initial diagnosis at dealership.
  ✅ What actually fixed it The misfire was caused by oil and coolant found inside the cylinder. The dealership determined a new engine was required. This aligns with the severe outcomes described in the TSBs for oil consumption issues.
• BobIsTheOilGuy Forum (2019 Ford F-150 with 2.7L EcoBoost) — Intermittent misfire/stutter under heavy load (WOT above 3500 rpm), eventually setting P0301, P0303, and P0306.
  ❌ Tried (didn't work) Changing fuel (using premium)., Adding fuel injector cleaner., Inspecting spark plugs (they looked fine).
  ✅ What actually fixed it The user noted that other owners of the same engine reported failing coil packs as the cause for similar symptoms, especially under load. The resolution points towards replacing the ignition coils, even if the spark plugs appear to be in good condition.

OEM Part Supersession History

• BL3Z-12029-A, BL3Z-12029-B → BL3Z-12029-C (which is sold as Motorcraft DG-549) — Standard part evolution and potential design improvements.

Model Year Variations Within This Range

• 2017 (3.0L V6): The TSBs regarding excessive oil consumption leading to misfires are particularly relevant for 3.0L engines built between April 2016 and January 2017. While the TSBs provided in the prompt (SSM 54504, SSM 46364) do not specify a date range for the MKZ, a related TSB for the similar 2.7L engine (19-2384) provides this specific build window, suggesting early production 2017 models are most at risk.