P0314 Single Cylinder Misfire (Cylinder Not Specified)

The P0314 trouble code means the engine control module (ECM/PCM) has detected a misfire affecting a single cylinder, but it has not been able to identify which cylinder is responsible.

This is an important distinction.

The engine computer has enough evidence to determine that the misfire is not occurring randomly across multiple cylinders, but it cannot reliably associate the detected crankshaft-speed fluctuation with a specific cylinder.

In other words, the ECM is effectively reporting:

“I detected a single-cylinder misfire, but I cannot determine which cylinder is misfiring.”

P0314 is therefore not a direct instruction to replace a spark plug, ignition coil, injector, or another specific component. The actual cause still needs to be established through diagnosis.

What Does P0314 Mean?

Modern engine computers can detect misfires by monitoring very small changes in crankshaft rotational speed.

During normal combustion, each cylinder contributes energy to the crankshaft.

When combustion is weak or absent in one cylinder, the crankshaft may momentarily slow down differently from the expected pattern.

The ECM compares these changes against the crankshaft position signal and its internal misfire-detection strategy.

With P0314, the ECM detects a pattern consistent with a single-cylinder misfire, but the available information is insufficient to identify the exact cylinder.

This is different from codes such as:

• P0301 – Cylinder 1 Misfire Detected

• P0302 – Cylinder 2 Misfire Detected

• P0303 – Cylinder 3 Misfire Detected

• P0304 – Cylinder 4 Misfire Detected

P0314 does not provide that cylinder number.

Why Can't the ECM Identify the Cylinder?

The ECM does not directly “see” combustion inside each cylinder.

It infers combustion quality from information such as:

• Crankshaft acceleration and deceleration

• Crankshaft position

• Engine speed

• Camshaft position

• Ignition timing

• Fuel injection timing

• Engine load

• Other sensor information

If the crankshaft-speed disturbance is too small, irregular, or ambiguous, the ECM may know that a misfire occurred but not be confident enough to assign it to a particular cylinder.

This can happen during certain operating conditions, particularly:

• Low engine speed

• Very light engine load

• Startup

• Rapid changes in engine speed

• Deceleration

• Rough road conditions

• Engine vibration

• Mechanical drivetrain disturbances

This is one reason P0314 can sometimes be more difficult to diagnose than a cylinder-specific P030X code.

P0314 Does Not Mean the Engine Has Only One Fault

The phrase “Single Cylinder Misfire” describes the misfire detection pattern.

It does not necessarily mean that only one component is defective.

For example, a single-cylinder misfire could be caused by:

• Spark plug

• Ignition coil

• Injector

• Fuel delivery

• Vacuum leak near one cylinder

• Compression problem

• Valve problem

• Carbon deposits

• Wiring

• Camshaft timing

• VVT operation

• Mechanical engine damage

The ECM simply does not know which cylinder is responsible yet.

Common Symptoms of P0314

Depending on how severe the misfire is, the driver may notice:

• Check Engine Light

• Rough idle

• Engine shaking

• Hesitation

• Poor acceleration

• Reduced engine power

• Uneven engine operation

• Engine stumble

• Increased fuel consumption

• Poor throttle response

• Exhaust popping

• Fuel smell

• Hard starting

• Engine stalling

• Flashing Check Engine Light

A mild misfire may be difficult to notice.

A severe misfire can make the engine shake noticeably, especially at idle.

Can P0314 Occur Without Noticeable Symptoms?

Yes.

The ECM can detect misfires that are too subtle for the driver to feel.

The vehicle may appear to drive normally while the engine computer records P0314.

This can happen when the misfire is:

• Very brief

• Intermittent

• Load-dependent

• RPM-dependent

• More pronounced under specific conditions

A lack of obvious symptoms does not necessarily mean that the code is meaningless.

Common Causes of P0314

Worn or Fouled Spark Plug

A spark plug can produce a weak or inconsistent spark, resulting in incomplete combustion.

Potential problems include:

• Excessive electrode wear

• Incorrect gap

• Carbon fouling

• Oil contamination

• Fuel fouling

• Cracked insulator

• Incorrect plug specification

If the engine has individual ignition coils, comparing the suspected cylinder's spark plug with the others can be useful once the cylinder is identified.

Weak Ignition Coil

A failing ignition coil can produce a single-cylinder misfire.

A coil may operate correctly at idle but fail under load when cylinder pressure increases and a stronger ignition voltage is required.

Coil failures can also be temperature-dependent.

If the vehicle uses interchangeable coils, moving a suspected coil to another cylinder can help determine whether the misfire follows the coil.

Faulty Fuel Injector

An injector that is restricted, sticking, leaking, or electrically defective can cause one cylinder to receive too much or too little fuel.

Possible injector problems include:

• Restricted nozzle

• Internal leakage

• Electrical failure

• Poor connector contact

• Sticking injector

• Incorrect fuel delivery

A cylinder receiving insufficient fuel can misfire even when the ignition system is working correctly.

Vacuum Leak Near One Cylinder

An intake leak near a particular cylinder can produce a lean mixture in that cylinder.

Possible sources include:

• Intake manifold gasket

• Vacuum hose

• PCV connection

• Intake runner seal

A larger intake leak may affect several cylinders, while a localized leak can create a cylinder-specific problem.

Low Fuel Pressure

Low fuel pressure can cause misfires, although it more commonly affects multiple cylinders.

Potential causes include:

• Weak fuel pump

• Restricted filter

• Faulty pressure regulator

• Fuel-pressure control problem

• Electrical supply problem

If P0314 appears together with fuel-pressure or lean-mixture codes, fuel delivery should be investigated.

Compression Loss

A cylinder that cannot maintain sufficient compression may misfire regardless of how good the ignition and fuel systems are.

Possible mechanical causes include:

• Burned valve

• Worn piston rings

• Damaged piston

• Valve-seat problem

• Head-gasket failure

• Excessive cylinder wear

A compression test and, when necessary, a leak-down test can help identify these problems.

Valve Problems

A valve that does not seal correctly can cause a single-cylinder misfire.

Possible causes include:

• Burned exhaust valve

• Bent valve

• Carbon buildup

• Valve-seat damage

• Valve-train problem

Mechanical problems become more likely when ignition and fuel components test normally.

Variable Valve Timing Problems

A VVT system can influence cylinder filling and combustion.

Problems with:

• VVT solenoids

• Camshaft actuators

• Oil passages

• Oil pressure

• Camshaft position sensors

• Mechanical timing

can contribute to misfire conditions.

If P0314 occurs together with camshaft or timing-related codes, the valve-timing system deserves attention.

Incorrect Camshaft or Crankshaft Timing

A timing chain or belt problem can affect combustion timing.

Possible causes include:

• Stretched timing chain

• Incorrectly installed timing belt

• Damaged timing components

• Camshaft/crankshaft synchronization problems

• VVT actuator problems

A timing problem can sometimes produce multiple misfires rather than a consistently isolated cylinder, but it should still be considered when other evidence points in that direction.

Wiring and Connector Problems

An intermittent electrical connection can produce a misfire without leaving an obvious physical sign.

Possible areas include:

• Ignition coil wiring

• Injector wiring

• Sensor wiring

• Ground connections

• Engine harness

• Connector terminals

Heat and vibration can make an intermittent electrical problem particularly difficult to reproduce.

Fuel Contamination

Contaminated fuel can interfere with combustion.

Possible problems include:

• Water contamination

• Incorrect fuel

• Poor-quality fuel

• Fuel-system contamination

If several cylinders are affected after refueling, fuel quality becomes more relevant.

Rough Road Conditions

Rough-road conditions can complicate misfire detection.

The ECM normally has strategies to distinguish genuine combustion misfires from crankshaft-speed variations caused by the vehicle travelling over uneven surfaces.

This is one reason rough-road-related codes can sometimes appear alongside misfire codes.

A vehicle that has P0314 together with P0318 should be evaluated for both genuine engine misfire and problems with rough-road signal information.

How P0314 Is Diagnosed

The main challenge is that the ECM has not identified the cylinder.

The first objective is therefore to determine which cylinder is actually misfiring.

1. Scan for All Stored Codes

Start by scanning all available control modules.

Look for:

• P0314

• P0300

• P0301–P0308

• Ignition coil codes

• Injector codes

• Fuel-pressure codes

• Air/fuel mixture codes

• Camshaft codes

• Crankshaft codes

• VVT codes

• Sensor codes

• Rough-road codes

Another DTC may provide the missing clue.

2. Check Freeze-Frame Information

Freeze-frame data can show what the engine was doing when the misfire was detected.

Useful information includes:

• Engine RPM

• Coolant temperature

• Engine load

• Vehicle speed

• Throttle position

• Fuel trims

• System voltage

For example, if P0314 consistently occurs during cold idle, the diagnosis should focus on faults that are most likely to affect cold combustion.

3. Monitor Misfire Counters

Many modern scan tools can display misfire counters for individual cylinders.

This is one of the most useful diagnostic tools when P0314 is stored.

The ECM may have detected the misfire but not stored a cylinder-specific P030X code.

Live misfire data may nevertheless show one cylinder accumulating significantly more misfire events than the others.

4. Look for Cylinder Balance Differences

Depending on the diagnostic equipment and engine, cylinder contribution or balance information can help identify the weak cylinder.

A cylinder producing less power than the others can provide a useful direction for further testing.

5. Inspect the Spark Plugs

Once a likely cylinder has been identified, inspect its spark plug.

Compare it with the plugs from the other cylinders.

Look for:

• Fuel wetness

• Oil contamination

• Carbon deposits

• Unusual wear

• Abnormal electrode condition

• Incorrect gap

The condition of the plug can sometimes indicate whether the problem is related to fuel, oil, ignition, or combustion.

6. Test or Swap the Ignition Coil

If the vehicle uses interchangeable ignition coils, a controlled coil swap can be extremely useful.

For example, if cylinder 2 appears to be the likely source:

Move its coil to cylinder 3.

Then monitor the misfire data again.

If the misfire follows the coil, the coil becomes a strong suspect.

If the misfire stays on cylinder 2, the investigation should continue elsewhere.

7. Check the Injector

The injector should be evaluated for both electrical operation and fuel delivery.

Depending on the vehicle, testing may include:

• Injector resistance where applicable

• Injector control signal

• Injector balance

• Fuel delivery

• Injector leakage

Resistance alone is not always enough to prove that an injector is functioning correctly.

8. Check Fuel Pressure

Fuel pressure should be checked under the conditions where the misfire occurs.

A system that maintains adequate pressure at idle may have a problem under acceleration or during startup.

Always compare the measurement with the manufacturer's specification.

9. Check for Intake Leaks

If one cylinder is suspected, pay particular attention to the intake area serving that cylinder.

Smoke testing can be useful for detecting leaks that are difficult to see visually.

10. Perform Compression Testing

If ignition and fuel systems appear normal, mechanical testing becomes increasingly important.

A compression test can identify a cylinder that produces significantly less compression than the others.

A leak-down test can then help determine where the pressure is escaping.

11. Check Camshaft and Crankshaft Synchronization

If there are timing-related symptoms or codes, verify synchronization.

A cam/crank correlation problem can affect combustion and misfire detection.

An oscilloscope can be useful when the mechanical timing or sensor signals are difficult to evaluate with a scan tool alone.

12. Consider VVT Operation

If the engine uses variable valve timing, compare commanded and actual camshaft position where the diagnostic system supports it.

A VVT problem can produce poor combustion without necessarily causing an obvious ignition-system fault.

13. Check Wiring Under Real Operating Conditions

Intermittent problems can disappear when the vehicle is stationary.

A technician may need to inspect the wiring while:

• The engine is running

• The harness is gently moved

• Engine temperature changes

• Engine load changes

Care must be taken around moving and hot engine components.

P0314 vs. P0300

These codes describe different misfire patterns.

P0314 indicates a single-cylinder misfire with the cylinder not specified.

P0300 indicates random or multiple-cylinder misfire.

Therefore, P0314 does not mean that several cylinders are misfiring randomly.

The distinction can be particularly useful when interpreting scan-tool data.

P0314 vs. P0316

These codes are also different.

P0314 describes a single-cylinder misfire where the cylinder cannot be identified.

P0316 describes a misfire detected during the first 1,000 engine revolutions after startup.

The two codes can potentially occur together.

For example, an engine could experience a single-cylinder misfire immediately after startup, producing both timing-related and cylinder-identification information depending on the ECM's diagnostic strategy.

P0314 and P0301–P0308

A P030X code is more specific because it identifies the cylinder.

For example:

• P0301 = Cylinder 1

• P0302 = Cylinder 2

• P0303 = Cylinder 3

• P0304 = Cylinder 4

If a cylinder-specific code appears later after P0314 has been stored, it can provide a much stronger diagnostic direction.

Can P0314 Be Caused by a Bad Ignition Coil?

Yes, but the code itself does not prove that the coil is bad.

A weak coil is one possible cause of a single-cylinder misfire.

The most useful confirmation is to determine whether the misfire follows the coil when it is moved to another cylinder, provided the coils are interchangeable and the manufacturer's diagnostic procedure allows this test.

Can P0314 Be Caused by a Bad Spark Plug?

Yes.

A worn, fouled, damaged, or incorrectly gapped spark plug can produce a single-cylinder misfire.

However, if a new plug repeatedly becomes fouled, the underlying cause should be investigated rather than repeatedly replacing plugs.

Can P0314 Be Caused by Low Compression?

Yes.

A mechanical problem in one cylinder can cause exactly the type of combustion loss that the ECM interprets as a single-cylinder misfire.

If ignition and fuel testing do not reveal a problem, compression and leak-down testing become important.

Is P0314 Serious?

It can be, depending on the severity and frequency of the misfire.

A mild, occasional misfire may allow the vehicle to continue operating without obvious drivability problems.

A severe or continuous misfire is much more serious.

A misfiring cylinder can send unburned fuel into the exhaust system, where it can overheat and damage the catalytic converter.

Continued misfire can also increase:

• Fuel consumption

• Exhaust emissions

• Engine vibration

• Engine temperature in certain conditions

• Risk of catalytic-converter damage

Can You Drive With P0314?

If the engine is running smoothly and the Check Engine Light is steady, a short drive to a repair facility may be possible.

However, continued driving should be avoided if:

• The Check Engine Light is flashing

• The engine is shaking severely

• Power loss is significant

• The engine is stalling

• There is a strong raw-fuel smell

• Misfires occur continuously

A flashing Check Engine Light generally indicates a severe misfire condition that can damage the catalytic converter.

Why P0314 Can Be Difficult to Diagnose

The biggest challenge is the lack of cylinder identification.

The ECM has detected the combustion problem but has not been able to reliably match the crankshaft-speed variation to a particular cylinder.

This means a technician should avoid simply replacing ignition or fuel components at random.

A better strategy is to combine:

• Misfire counters

• Freeze-frame data

• Spark-plug inspection

• Coil testing

• Injector testing

• Fuel-pressure testing

• Compression testing

• Intake-leak testing

• Cam/crank synchronization

• VVT data

The goal is to turn “one cylinder is misfiring, but I don't know which one” into a specific cylinder and then determine why that cylinder is failing to produce normal combustion.

Final Takeaway

P0314 – Single Cylinder Misfire (Cylinder Not Specified) means the ECM/PCM has detected a misfire pattern consistent with one cylinder, but it cannot reliably determine which cylinder is responsible.

The code does not automatically identify a bad spark plug, ignition coil, injector, or mechanical engine component.

Possible causes range from relatively simple problems such as a worn spark plug or weak ignition coil to injector faults, vacuum leaks, fuel-pressure problems, compression loss, valve problems, VVT faults, and camshaft/crankshaft timing issues.

The most effective diagnostic approach is to first identify the affected cylinder using live misfire counters and other scan-tool data, then test that cylinder's ignition, fuel, air, and mechanical condition.

If the engine is experiencing a severe misfire or the Check Engine Light is flashing, driving should be avoided because prolonged misfire can cause expensive catalytic-converter damage.