P0305 to P0308: misfire on cylinders 5 to 8 and V-engine numbering

If your car has more than four cylinders, misfire codes run past P0304, and the extra challenge is not diagnostic — it is geometric.

On a V6 or V8, cylinder 5 is not the fifth one you can see. Getting this wrong means replacing a perfectly good coil on the wrong bank, then repeating the exercise.

The diagnostic method itself is unchanged: P0301 to P0304 cylinder misfire diagnostics.

Finding the cylinder

There is no universal layout. The common conventions:

• Many V-engines number one bank 1–3 or 1–4, and the other bank continues from there. Cylinder 5 is then the first cylinder of the second bank.
• Others alternate across banks: 1 on the left, 2 on the right, 3 on the left, and so on.
• Bank 1 is defined as the bank containing cylinder 1, which sounds circular and is the only rule that holds everywhere.

Look up the firing order and cylinder layout for your specific engine before touching anything. This is a two-minute search that prevents a wasted afternoon.

The oxygen sensor codes give a cross-check: a bank 2 sensor code alongside a P0305 tells you cylinder 5 is on bank 2 for your engine.

Why a V-engine misfire is worth catching early

More cylinders means each contributes less, which means a single misfiring cylinder is easier to miss from the driver’s seat. A four-cylinder with one down is unmistakable; a V8 with one down can feel like slightly rough idle.

Meanwhile the consequences are the same:

• Unburnt fuel reaching the catalyst on that bank, which overheats and destroys it. This is the expensive one.
• Oxygen sensor codes on the affected bank as the mixture reads wrong.
• Fuel trim pushed to compensate for one cylinder’s problem.

If the misfire light flashes rather than staying steady, the ECU is telling you catalyst damage is happening right now. Stop driving: check engine blinking vs solid.

The swap test, adapted

The single most efficient diagnostic, and it costs nothing.

1. Note the misfiring cylinder and its counter value.
2. Move its ignition coil to a different cylinder — ideally the neighbour.
3. Clear codes and drive until the monitor runs.
4. Read again. If the misfire followed the coil, the coil is faulty. If it stayed, the coil is fine.
5. Repeat with the spark plug, then the injector.

On a V-engine, swap within the same bank where possible. Swapping across banks introduces a second variable if there is a bank-specific issue.

Ignition coil and spark plug diagnostics.

Reading multiple codes together

The combination narrows the cause quickly.

Codes	Likely cause
One cylinder only	Coil, plug or injector on that cylinder
Two adjacent cylinders	Head gasket between them, or a shared coil pack
All cylinders on one bank	Bank-specific: camshaft, injector rail, wiring
P0300 plus specific cylinders	Something common plus a weak cylinder
P0300 alone	Fuel, air or ignition affecting everything

P0300 random misfire deep dive.

Causes ordered for higher-cylinder engines

Coils and plugs remain the most common, and on a V-engine the rear bank plugs are frequently the oldest — access is poor, so they get skipped during service.

Carbon on the intake valves on direct injection engines, which affects the cylinders unevenly: GDI carbon buildup.

Injectors, particularly on high-mileage engines.

Compression, if a cylinder never recovers regardless of parts.

Cylinder deactivation systems on engines that have them — a failed lifter produces a permanent misfire on exactly the cylinders the system shuts down: P3400 cylinder deactivation.

That last one is worth knowing on large V8s. A misfire on the specific cylinders the deactivation system uses is a mechanical fault in that system, not an ignition problem.

Before you order parts

1. Confirm the physical cylinder from the layout for your engine.
2. Read misfire counters per cylinder, not just the code.
3. Check freeze frame — cold, hot, loaded or idle?
4. Swap a component and re-test before buying.
5. Check fuel trims for the affected bank.

The practical next step: pair an ELM327 adapter, open the free tier of the app and watch misfire counters per cylinder in real time. On a multi-cylinder engine, that counter finds the cylinder faster than any amount of listening.