P0308 on 2021-2025 Ford E-350 7.3L V8: Cylinder 8 Misfire Causes and Fixes

What's Unique About the 2021-2025 Ford E-350

While a misfire code on many vehicles points to a simple tune-up part, the 7.3L 'Godzilla' V8 has two very distinct and common possibilities. The first is a high failure rate of the factory spark plug wires due to heat. The second, and more serious, is a known issue with premature camshaft and valve lifter (tappet) wear, which can cause this exact code and requires major engine repair. 🎬 Watch: A teardown of a Godzilla engine with camshaft failure. This makes it critical to not just assume it's a simple fix without proper diagnosis.

Symptoms You May Notice

• Rough or shaky idle
• Engine hesitation or stumbling during acceleration
• Flashing Check Engine Light (indicates a severe misfire)
• Loss of engine power
• Engine may be harder to start
• Audible ticking or tapping noise from the engine bay, which strongly suggests the more serious lifter/camshaft issue.

Most Likely Causes

1. Faulty Spark Plug Wire 🔴 High Probability → Shop Spark Plug The original equipment spark plug wires on the 7.3L V8 are known to be susceptible to heat damage from the exhaust manifolds, causing them to become brittle and fail prematurely. Ford has issued TSBs for other models with this engine related to wire failure, and has released several revised part numbers to address the problem.
   How to confirm: Inspect the wire for cylinder 8 for any visible damage, burns, or looseness. A definitive test is to swap the cylinder 8 wire with an adjacent cylinder (like cylinder 6) and see if the misfire code changes to P0306 after clearing codes and test driving.
   Typical fix: Replace the faulty wire. It is highly recommended to replace all eight wires at the same time with a high-quality set 🎬 Watch: Step-by-step guide to replacing spark plugs and wires. from a brand like Motorcraft (latest revision) or a reputable aftermarket performance brand like MSD or Taylor for better heat resistance.
   Est. part cost: $50-$150 for a full set
2. Faulty Ignition Coil 🟡 Medium Probability → Shop Ignition Coil
   How to confirm: Swap the ignition coil from cylinder 8 with another cylinder (e.g., cylinder 7). Clear the codes and drive the vehicle. If the trouble code changes to P0307, the ignition coil is the culprit.
   Typical fix: Replace the faulty ignition coil. They are sold individually. The OEM part is a Motorcraft DG-581.
   Est. part cost: $30-$70
3. Worn or Fouled Spark Plug 🟡 Medium Probability → Shop Spark Plug
   How to confirm: After ruling out the wire and coil, remove the spark plug from cylinder 8. Inspect it for wear on the electrode, cracks in the porcelain, or heavy deposits of carbon or oil.
   Typical fix: Replace the spark plug. It is best practice to replace all eight spark plugs at the same time to ensure consistent performance. The OEM plug is Motorcraft SP-587.
   Est. part cost: $5-$20 per plug
4. Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector
   How to confirm: Listen for a clicking sound from the injector with a mechanic's stethoscope to confirm it's operating. A more advanced method is to measure the injector's resistance or perform a flow test. Swapping injectors between cylinders is also possible but more labor-intensive.
   Typical fix: Replace the faulty fuel injector.
   Est. part cost: $40-$100

Rare But Worth Checking

• Internal Engine Damage (Worn Camshaft/Lifters): This is a known, serious issue with the 7.3L Godzilla engine, documented in Ford TSBs like 22-2223 and discussed extensively by owners. The failure often involves the hardening on the lifter's roller bearing delaminating (spalling), which then destroys the corresponding camshaft lobe. If you hear a distinct ticking or tapping noise from the engine along with the misfire, this is a strong possibility. Diagnosis requires checking for valvetrain issues, often with a borescope or by removing the valve covers. This is a major repair, often requiring engine replacement under warranty.

Diagnosis Steps

1. Read the code from the OBD-II port using a scanner. Confirm P0308 is present and check for any other codes.
2. Listen for any unusual engine noises, such as a persistent ticking, which could indicate a serious mechanical issue.
3. Swap the ignition coil from cylinder 8 with another cylinder (e.g., cylinder 7). Clear the codes and run the engine. If the code changes to P0307, the coil is bad.
4. If the code remains P0308, swap the spark plug wire from cylinder 8 with a wire from another cylinder (of similar length, like cylinder 6). If the misfire follows the wire, the wire is bad.
5. If the code still remains P0308, remove and inspect the spark plug from cylinder 8. Replace it if it's worn, fouled, or damaged.
6. If ignition components are confirmed good, the next step is to check the fuel injector for cylinder 8. Listen for its operation and check the wiring.
7. If all of the above steps do not resolve the issue, a more serious mechanical problem is possible. A compression test should be performed to check the health of the cylinder. If compression is low, professional diagnosis is required to inspect for internal engine damage like worn camshafts or lifters.

Parts You'll Likely Need

• Spark Plug Wires (OEM #LC3Z-12286-D (latest revision, also known as WR-6170)) — The factory wires are a known weak point on the 7.3L V8, prone to heat damage that causes misfires. The 'D' revision offers improved heat resistance.
  Trusted brands: Motorcraft, MSD, Taylor, Granatelli
  OEM price range: $100-$180
  Aftermarket price range: $80-$200
• Ignition Coil (OEM #LC3Z-12029-A (Motorcraft DG-581)) — A common failure point for any modern engine. It's responsible for creating the high voltage needed to fire the spark plug.
  Trusted brands: Motorcraft, NGK, Denso
  OEM price range: $50-$80
  Aftermarket price range: $30-$70
• Spark Plug (OEM #SP-587) — A standard maintenance item that wears out over time and can cause a misfire.
  Trusted brands: Motorcraft, NGK
  OEM price range: $10-$20
  Aftermarket price range: $5-$15

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or starting to affect other cylinders due to a shared cause (like failing plug wires), a P0300 (Random/Multiple Misfire) code may appear.
• P0316 — This code indicates a misfire was detected within the first 1000 engine revolutions on startup. It often accompanies a specific cylinder misfire code like P0308, especially if the cause is mechanical (like a stuck lifter).
• P0358 — This code points specifically to a fault in the ignition coil primary or secondary circuit for cylinder 8, helping to narrow the diagnosis directly to the coil or its wiring.

Technical Service Bulletins (TSBs) & Recalls

• TSB 22-2223: Addresses valvetrain wear and lifter failure, which can present as a single-cylinder misfire.
• TSB 25-2572: Notes that misfire codes can be caused by excessive wear on the camshaft and/or valve tappets.
• TSB 20-2370: Addresses misfires on 2020 7.3L engines in F-53 chassis caused by damaged spark plug wires, requiring replacement of all 8 wires.
• TSB 21-2119: Also relates to misfires caused by faulty spark plug wires, indicating a persistent issue.
• SSM 51330: Special Service Message regarding a ticking noise that could be a cracked oil pump drive gear, which should be differentiated from a lifter tick.

Platform-Specific Known Issues

• Spark Plug Wire Failure: → Shop Spark Plug TSB 20-2370 was issued for the 2020 7.3L engine in F-53 chassis, and TSB 21-2119 also addresses misfires from plug wires. This indicates an inherent design weakness where heat from the exhaust manifold damages the wires, particularly for the rear cylinders like #8.
• Camshaft/Lifter Failure: → Shop Engine Camshaft TSB 22-2223 (which supersedes earlier versions) and TSB 25-2572 explicitly link misfire codes (P0301-P0308) to excessive wear on the camshaft and valve tappets (lifters). This is a well-documented issue among owners, often presenting as a misfire with a ticking noise, and can lead to catastrophic engine failure if not addressed.

Mechanic-Grade Diagnostic Values

• Ignition Coil Secondary Resistance (Aftermarket Example) — expected: 13.7K Ohms. Failure: A reading significantly different from this value suggests an internal coil failure.
• Ignition Coil Primary Resistance (Aftermarket Example) — expected: 0.53 Ohms. Failure: A significant deviation may indicate a faulty primary winding.
• Fuel Pressure (at fuel rail) — expected: 55-60 PSI at idle. Failure: Low fuel pressure can cause lean misfires, though it would likely affect more than one cylinder.
• Fuel Injector Flow Rate — expected: 35 lbs./hr.. Failure: This is a factory specification; a lower flow rate on a bench test would indicate a clogged or failing injector.
• Minimum Hot Idle Oil Pressure (Factory Spec) — expected: 8 PSI. Failure: This is the minimum factory specification. While technically 'in spec,' prolonged operation at this low pressure is believed to contribute to lifter/camshaft failure. Any reading below this indicates a serious oiling system problem.

Hidden / Shadow Codes Worth Checking

• Mode $06, Test ID $A2-$AF, Component ID $08: This is not a trouble code but a specific data point within the OBD-II system's Mode $06 that shows the raw misfire count for cylinder 8 during the current and last driving cycles. It can reveal misfires that are occurring but are not yet frequent enough to trigger the P0308 DTC and check engine light. (see via Advanced OBD-II scan tool or diagnostic software like FORScan.)
• P0284 - Cylinder #8 Contribution/Balance: This code is more specific than P0308 and may be set on some Ford vehicles. It directly indicates that cylinder 8 has failed a power contribution test, strongly suggesting a fuel or mechanical issue rather than a simple ignition fault. (see via Standard OBD-II scanner, but may be more consistently found with Ford-specific tools like IDS or FORScan.)

Scan Tool Commands That Help

• Ford IDS/FDRS or FORScan: Power Balance Test — This is the primary diagnostic function for a Ford misfire. It graphically displays the power contribution of each cylinder in real-time. A significant downward dip or a flat line for cylinder 8 confirms it is not contributing power. The tool also allows the user to disable individual injectors to see the effect on RPM, helping to isolate the fault.

Real Owner Repair Stories

• Reddit user /u/Only_Explanation_901 (Ford Dealer Technician) (2020 Ford F-250 7.3L Godzilla) — Check Engine Light, misfire code, physical engine damage found with a borescope.
  ❌ Tried (didn't work) Replaced fuel injector
  ✅ What actually fixed it The root cause was a failed lifter that wiped out the camshaft, a common issue the technician had seen multiple times. The ultimate repair was a complete engine replacement due to metal contamination.
• Ford Truck Enthusiasts forum user (2020 F-350 7.3L, 49,000 miles) — Rough idle, Check Engine Light with P0304 (misfire on cylinder #4, but the diagnostic principle is identical for P0308).
  ❌ Tried (didn't work) Replacing only the spark plug wire., Replacing the spark plug, plug wire, and ignition coil (misfire returned the same day).
  ✅ What actually fixed it The user's story did not have a final resolution posted, but it serves as a critical real-world example of how replacing all common ignition components (plug, wire, coil) did not fix the problem, strongly pointing to the deeper mechanical camshaft/lifter issue or a wiring harness fault.

OEM Part Supersession History

• LC3Z-6500-A / -B → LC3Z-6500-C — The valve tappets (lifters) were revised multiple times, likely to improve the roller and bearing assembly to address the widespread delamination and spalling failures.
  Heads up: When replacing failed lifters, it is critical to also inspect and likely replace the camshaft. A damaged camshaft lobe will immediately destroy new lifters.
• LC3Z-6250-A → PC3Z-6250-A — The camshaft was likely updated with improved surface hardening or material composition to better resist damage from failing lifter rollers.
• LC3Z-12286-A / -B / -C → LC3Z-12286-D (Motorcraft WR-6170) — Original spark plug wires were highly susceptible to heat damage from the exhaust manifolds. Later revisions include improved heat shielding and more durable boot materials to prevent arcing and premature failure.
  Heads up: Using older revision part numbers will likely lead to a repeat failure. It is critical to use revision 'D' or a high-quality aftermarket equivalent.

Model Year Variations Within This Range

• 2023-2024: A delivery hold and subsequent PCM reprogram (Customer Satisfaction Program 24B27) were issued for some 2023-2024 models. This software update is believed to increase idle oil pressure to help mitigate the lifter failure issue, though the minimum spec remains low.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Premature Camshaft/Lifter Failure 🔴 High → Shop Engine Camshaft — A widely documented issue across forums and YouTube, though the exact percentage of failures is unknown. Can occur at mileages as low as 30,000 miles, but is more common closer to the end of the powertrain warranty period (~60,000 miles). (Ref: TSB 22-2223, TSB 25-2572)
• Spark Plug Wire Degradation 🟠 Medium → Shop Spark Plug — Very common. Heat from the exhaust manifolds causes the factory wires, especially for cylinders 7 and 8, to become brittle and fail, leading to misfires. It is a frequent cause for P0300, P0307, and P0308 codes. (Ref: TSB 20-2370, TSB 21-2119)
• Variable Displacement Oil Pump Strategy 🟠 Medium — This is a design characteristic rather than a direct failure, but it is a suspected root cause of the lifter failures. The pump's strategy can result in very low oil pressure at idle (as low as 8 psi), potentially starving the upper valvetrain. (Ref: A PCM update was issued for some models to increase idle oil pressure, but its availability varies.)
• Cracked Oil Pump Drive Gear 🟡 Low — Less common, but documented. Can cause a ticking noise from the lower front of the engine that might be mistaken for a lifter tick. (Ref: SSM 51330)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this specific repair, used parts are generally not recommended. The primary causes are either wear-and-tear ignition components that should always be new, or a catastrophic internal engine failure where used parts carry a very high risk.

Donor-vehicle mileage cap: roughly under 50000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For ignition coils: Check for cracks in the housing, corrosion on the electrical connector, and damage to the boot.
• For engine assemblies: A complete service history showing frequent oil changes with quality oil is mandatory. Avoid engines from commercial fleet vehicles that have high idle hours.
• Listen to the donor engine run if possible, checking for any ticking or knocking noises.

OEM-only on this vehicle (don't cheap out):

• Camshaft and Lifters: Due to the catastrophic nature of the failure, using anything other than the latest revised OEM parts or a reputable performance aftermarket kit (like from Brian Tooley Racing) is extremely risky. Used lifters or camshafts should never be installed.

Aftermarket brands forum-validated for this vehicle:

• Spark Plug Wires: MSD, Taylor, Top Street Performance (with ceramic boots).
• Ignition Coils: Motorcraft (OEM), NGK, Denso.
• Cam/Lifter Kits: Brian Tooley Racing (BTR), COMP Cams.

Brands owners have reported issues with on this vehicle:

• Unbranded, low-cost ignition coils and spark plug wires from online marketplaces often have high failure rates and may not meet the heat resistance requirements for this engine.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0300 — Random or multiple cylinder misfire code that often appears alongside P0308 when heat damage affects multiple spark plug wires.
• P0306 — A cylinder 6 misfire code; used during diagnosis to confirm a faulty wire by swapping the cylinder 8 wire to cylinder 6.
• P0307 — A cylinder 7 misfire code; often appears with P0308 because both rear cylinders are highly susceptible to exhaust manifold heat damage and lifter wear.
• P0301 — One of the misfire codes (P0301-P0308) explicitly linked to camshaft and valve tappet failure in TSB 22-2223.

Frequently Asked Questions