What a Cylinder 4 Misfire Means on a Hyundai Santa Fe

A cylinder 4 misfire on a Hyundai Santa Fe means that the engine’s fourth cylinder is not burning its air‑fuel mixture properly, causing rough running, loss of power, and often a check-engine light with codes like P0304. This issue can stem from ignition, fuel delivery, mechanical problems, or sensor faults, and should be diagnosed and repaired promptly to avoid engine damage and higher repair costs.

Understanding the Basics: What Is a Misfire?

At its core, a misfire happens when one or more cylinders in the engine fail to ignite the air–fuel mixture at the right time or with enough intensity. Your Hyundai Santa Fe’s engine relies on precise combustion in each cylinder, and when one cylinder—here, cylinder 4—doesn’t do its job, the entire engine operation becomes unbalanced.

How Cylinders Work in a Hyundai Santa Fe Engine

The Hyundai Santa Fe has used several engine types over the years, including inline‑4 and V6 gasoline engines (and in some markets, diesel variants). Regardless of engine type, each cylinder has three essentials: air, fuel, and spark. When those three come together at the correct moment and in the correct ratio, the cylinder produces power. If one of those elements is missing or out of sync, the result is a misfire.

The following list explains how a misfire disrupts this normal process.

• Air–fuel mixture: Needs to be delivered in the correct ratio and quantity to each cylinder.
• Ignition spark: Must be strong and precisely timed to ignite the mixture.
• Compression: Valves, piston rings, and head gasket must seal properly to compress the mixture.
• Exhaust flow: Burned gases must exit cleanly so the next charge can enter.

Together, these steps create a continuous cycle of controlled explosions. A misfire is simply a failure in one or more of those steps in a given cylinder, which, over time, can affect the whole engine.

What “Cylinder 4” Specifically Refers To

“Cylinder 4” is not random shorthand; it is a specific chamber in the engine, identified by standardized numbering. When a scan tool shows code P0304 (or similar), it indicates that misfiring is being detected in that individual cylinder rather than across the entire engine.

Cylinder Numbering on Common Santa Fe Engines

Depending on the engine layout, the position of cylinder 4 changes. This is important for technicians when swapping coils, checking plugs, or testing injectors.

The following list outlines how cylinder numbering usually works on popular Hyundai Santa Fe engines.

• Inline‑4 engines (e.g., 2.0L, 2.4L GDI/MPi): Cylinders are in a straight line. Counting starts from the end of the engine closest to the timing belt/chain:
  

  • Cylinder 1 at the timing side
  • Cylinder 4 at the opposite end (closest to the transmission)

• V6 engines (e.g., 3.3L, 3.5L GDi/MPi): Two banks of cylinders:
  

  • Bank 1 contains cylinder 1 (usually the bank closer to the firewall)
  • Hyundai typically numbers cylinders 1–3 on one bank and 4–6 on the other
  • Cylinder 4 is the first cylinder on the opposite bank from cylinder 1

While the exact physical spot varies by engine, the key point is that “cylinder 4” is a precise location, allowing a focused inspection of that part of the ignition and fueling system.

Common Symptoms of a Cylinder 4 Misfire on a Santa Fe

Hyundai Santa Fe owners usually notice several drivability changes when cylinder 4 misfires. Some symptoms are subtle at first and then worsen if left unresolved.

The list below describes typical signs drivers may observe when this fault develops.

• Check-engine light (CEL): Often flashes when the misfire is severe, and stays solid when the issue is stored as a code such as P0304.
• Rough idle: The engine may shake or feel uneven when stopped at a light or in park.
• Loss of power: Acceleration feels sluggish, especially under load or going up hills.
• Hesitation or jerking: The vehicle may stumble when you press the gas pedal.
• Increased fuel consumption: The engine may run richer as it compensates for the misfire.
• Possible exhaust odor or sound change: You might smell unburned fuel or hear popping from the exhaust.
• Engine vibration: Noticeable shaking in the steering wheel, seat, or cabin.

Each of these symptoms signals that one cylinder is not contributing its share of power, and together they can dramatically affect how a Santa Fe drives and how efficiently it uses fuel.

Why Cylinder 4 Misfires Happen: Main Causes

A cylinder 4 misfire can come from several subsystems. On Hyundai Santa Fe models, ignition-related issues are very common, but fuel and mechanical problems or sensors can be at fault as well. Identifying which category the fault falls into is the key to an accurate and cost-effective repair.

Ignition System Problems

The ignition system delivers the spark needed to ignite the air–fuel mixture. Modern Santa Fe engines often use coil-on-plug designs, which eliminate spark plug wires but introduce individual coil packs for each cylinder.

The list that follows details ignition issues that frequently trigger a cylinder 4 misfire.

• Worn or fouled spark plug in cylinder 4: Oil fouling, carbon buildup, or a worn electrode can weaken or prevent spark.
• Failing ignition coil on cylinder 4: Internal breakdown can cause an intermittent or weak spark, especially under load or when hot.
• Moisture or corrosion: Water intrusion in the coil connector or plug well can short the spark path.
• Poor electrical connection: Loose or damaged wiring to the coil can disrupt voltage delivery.

Ignition issues are often the first area technicians test because they are common, relatively inexpensive to fix, and can be confirmed quickly by swapping parts between cylinders.

Fuel Delivery and Injector Issues

Even with a perfect spark, a cylinder cannot fire properly without a precise fuel dose. Hyundai’s gasoline direct-injection (GDI) systems, used in many later Santa Fe models, run at high pressure and can be sensitive to fuel quality and deposits.

The following list outlines fuel-related causes tied specifically to a misfire in cylinder 4.

• Clogged or weak fuel injector: Restricted flow prevents enough fuel from reaching cylinder 4.
• Injector electrical fault: A bad connector, damaged wiring, or failed driver in the ECU may prevent the injector from opening properly.
• Fuel pressure problems: Overall low fuel pressure can worsen misfires, though this usually affects multiple cylinders.
• Contaminated fuel: Water or debris in the fuel system can contribute to injector malfunction.

Fuel delivery issues can mimic ignition problems, which is why technicians often test or swap injectors and check fuel trims when a misfire stays on a single cylinder.

Mechanical and Compression Problems

If air cannot be compressed properly in the cylinder, it will not burn efficiently, no matter how good the spark and fuel are. Mechanical faults are generally more serious and sometimes more expensive to repair.

The list below covers mechanical reasons for a cylinder 4 misfire in a Santa Fe.

• Low compression in cylinder 4: Caused by worn piston rings, damaged cylinder walls, or a cracked piston.
• Valve problems: Burned, bent, or stuck intake or exhaust valves can result in poor sealing.
• Head gasket leak: A failing head gasket between cylinder 4 and a coolant passage or adjacent cylinder can reduce compression.
• Camshaft or timing issues: Incorrect valve timing from a stretched chain, worn tensioner, or timing error can affect one or more cylinders.

Mechanical issues usually present with more persistent misfires and may be confirmed with compression and leak-down tests that compare cylinder 4 to the others.

Sensor and Control System Faults

Modern Hyundai Santa Fe models rely on data from various sensors to adjust spark timing, fuel delivery, and air management. A sensor issue may cause the ECU to miscalculate, worsening or triggering misfire conditions.

The list that follows highlights control-related contributors to cylinder 4 misfires.

• Faulty oxygen (O2) or air‑fuel ratio sensors: Can lead to incorrect fuel trims, especially on one bank of a V6.
• Mass airflow (MAF) or manifold absolute pressure (MAP) sensor errors: Cause wrong load and air calculations.
• Crankshaft or camshaft position sensor problems: Disrupt timing information, affecting spark synchronization.
• ECU software issues: Some Hyundai models have had updates or TSBs (Technical Service Bulletins) addressing misfire-related calibration problems.

While these faults may not always produce a misfire in just one cylinder, they can aggravate or reveal underlying weaknesses specifically in cylinder 4 if it is already marginal.

How Technicians Diagnose a Cylinder 4 Misfire

Accurate diagnosis requires more than just reading an error code; professionals will use scan tools, visual inspection, and targeted tests to confirm what is wrong with cylinder 4 on a Santa Fe.

Initial Scan and Data Review

A scan tool provides the first clues, beyond simply confirming the presence of P0304 or related codes.

The following list shows how diagnostic data is typically used in early troubleshooting.

• Read stored and pending codes: Look for P0304 alongside any fuel, ignition, or sensor codes.
• Check misfire counters: Live data shows how often each cylinder misfires, confirming that cylinder 4 is the problem spot.
• Monitor fuel trims and O2 sensor data: Helps determine whether the engine is running lean or rich overall or on one bank.
• Observe engine operating conditions: Note if misfires occur mainly at idle, under load, or at higher RPM.

This electronic snapshot tells technicians whether they are likely dealing with an isolated cylinder fault or a broader system issue, narrowing down where to look next.

Simple Swap Tests and Visual Inspection

Because Hyundai Santa Fe engines use individual ignition coils and plugs, technicians often perform quick part-swapping to see if the misfire “follows” the component.

The list below outlines common hands-on checks performed early in the diagnosis.

• Swap ignition coil from cylinder 4 to another cylinder: If the misfire code moves, the coil is suspect.
• Inspect and, if needed, swap spark plug: A visibly fouled or cracked plug is a red flag.
• Check wiring and connectors: Look for broken clips, corroded pins, or damaged insulation.
• Inspect injector and its connector: Ensure it is properly seated and not leaking externally.

If the misfire remains on cylinder 4 despite swapping parts, attention usually shifts to fuel delivery, compression, or less visible electrical issues.

Compression, Leak-Down, and Advanced Testing

When the basic checks do not explain the misfire, deeper mechanical and electronic testing comes into play, especially on higher‑mileage Santa Fe models or those with known engine wear concerns.

The following list summarizes more advanced diagnostic steps.

• Compression test on all cylinders: Compares cylinder 4’s pressure to the others for signs of internal damage.
• Leak‑down test: Pinpoints where compression loss occurs (intake valve, exhaust valve, rings, or head gasket).
• Noid light or scope testing on injector circuit: Confirms that the ECU is commanding the injector correctly.
• Oscilloscope on ignition and crank/cam signals: Looks for timing irregularities or signal dropouts.

These tests clarify whether repairing a misfire will be a relatively minor ignition service or a larger mechanical overhaul, giving owners a clearer picture of the repair path and cost.

Risks of Driving with a Cylinder 4 Misfire

Continuing to drive a Hyundai Santa Fe with an unresolved cylinder 4 misfire is risky, especially if the check-engine light is flashing. Over time, the consequences can extend well beyond a simple rough idle.

The list below explains the most serious potential outcomes of ignoring a misfire.

• Catalytic converter damage: Unburned fuel entering the exhaust can overheat and melt the catalyst, leading to expensive repairs.
• Engine wear and damage: Persistent misfires can cause uneven load, carbon buildup, and, in severe cases, piston or valve damage.
• Reduced fuel economy: The engine may inject extra fuel to compensate, wasting gas.
• Safety concerns: Loss of power or hesitation can be hazardous when merging, passing, or climbing hills.
• Failed emissions testing: Many regions will not pass a vehicle with active misfire codes or poor combustion readings.

Given these risks, addressing a cylinder 4 misfire promptly is usually more economical and safer than delaying repairs until other components fail.

Typical Repairs and Costs for Santa Fe Cylinder 4 Misfires

Repairing a cylinder 4 misfire on a Hyundai Santa Fe can range from a quick tune-up to significant engine work. The exact cost depends heavily on what is found during diagnosis and on local labor rates.

Common, Relatively Affordable Fixes

Many misfires, particularly on low‑ to mid‑mileage vehicles, are resolved with basic ignition or fuel-component replacements.

The following list outlines frequent lower‑cost solutions owners may encounter at a repair shop.

• Replace spark plug in cylinder 4 (often all plugs): Recommended interval varies, but misfires often appear when plugs are overdue.
• Replace ignition coil on cylinder 4: Some owners choose to replace the full set if one has failed and mileage is high.
• Clean or replace fuel injector on cylinder 4: Especially on GDI engines prone to deposits.
• Address wiring or connector issues: Repairing or replacing damaged harness sections or corroded connectors.

These fixes can often be completed in a single visit and, when combined with updated maintenance, may restore smooth operation for many thousands of miles.

More Extensive or Costly Repairs

If the misfire is caused by mechanical damage or severe internal wear, the repair scope can expand, especially on higher-mileage or neglected Santa Fe engines.

The next list explains more involved repairs sometimes necessary in stubborn cylinder 4 misfire cases.

• Valve repairs or cylinder head work: Requires removing the head to address burned valves, worn guides, or seat damage.
• Head gasket replacement: Necessary if a leak is causing compression loss or mixing coolant and combustion gases.
• Timing chain/belt and related components: If poor timing is linked to stretched chains, worn tensioners, or skipped teeth.
• Engine overhaul or replacement: Considered when multiple cylinders have low compression or when internal damage is widespread.

These repairs demand careful cost–benefit analysis, weighing the Santa Fe’s age, mileage, and overall condition against the price of major engine work or replacement.

Preventing Future Misfires on a Hyundai Santa Fe

While not every misfire is preventable, Hyundai Santa Fe owners can significantly reduce the likelihood of cylinder 4 issues by following maintenance schedules and addressing small problems early.

The following preventive measures help keep ignition, fueling, and engine internals in better condition over the long term.

• Follow Hyundai’s service intervals: Replace spark plugs, filters, and fluids at or before recommended mileage.
• Use quality fuel: Top-tier gasoline and, if approved, periodic fuel-system cleaners can help reduce deposits, especially on GDI engines.
• Promptly address warning lights: A steady or flashing check-engine light should be scanned and diagnosed rather than ignored.
• Monitor for oil consumption: Excessive oil burning can foul plugs and reduce compression over time.
• Keep ignition components dry and intact: Avoid washing the engine bay aggressively and repair any broken coil or harness seals.

These relatively simple habits can extend the life of key engine components, reduce the risk of misfires, and help maintain fuel efficiency and reliability.

Summary

A cylinder 4 misfire on a Hyundai Santa Fe means the fourth cylinder is not combusting its air–fuel mixture correctly, typically flagged by a code like P0304 and symptoms such as rough idle, loss of power, and a check-engine light. The underlying causes usually fall into four categories: ignition faults (spark plug or coil issues), fuel delivery problems (injector faults), mechanical defects (low compression, valve or head gasket trouble), or sensor and control-system errors. Proper diagnosis involves code scanning, targeted component swaps, and, when needed, compression and electrical testing. Driving for long periods with a cylinder 4 misfire can damage the catalytic converter and engine, so timely repair—often a new plug, coil, or injector—is recommended. With consistent maintenance and quick response to warning signs, Santa Fe owners can minimize misfires and keep their engines running smoothly.

What is a misfire on a Hyundai cylinder 4?

A Hyundai cylinder 4 misfire, often indicated by the P0304 code, is typically caused by ignition or fuel system issues like a faulty spark plug, bad ignition coil, or a clogged fuel injector. However, mechanical problems such as a burnt exhaust valve or a leaking head gasket are also possible causes. To troubleshoot, start with the easiest fixes like inspecting the spark plug and swapping the ignition coil to see if the misfire moves to another cylinder. 
This video explains what a P0304 code is and how to test for causes: 43sHVAC Mechanic YouTube · Mar 11, 2024
Common causes and troubleshooting steps
1. Ignition system problems

• Worn spark plug: A common cause, so check the condition of the spark plug in cylinder 4. 
• Faulty ignition coil: The ignition coil is responsible for sending a high-voltage spark to the spark plug. 
  • Troubleshooting: Swap the ignition coil from cylinder 4 with one from another cylinder. If the misfire code changes to a different cylinder (e.g., P0301, P0302), the coil is the problem. 
• Bad spark plug wires: In older models, a faulty wire can cause a misfire. 

This video shows how to swap the ignition coil to check for a bad coil: 57sdial2fastYouTube · Jan 6, 2023
2. Fuel system problems

• Clogged fuel injector: The injector may not be delivering enough fuel for proper combustion.
  • Troubleshooting: Check for a faulty injector on cylinder 4. Cleaning the injector may solve the problem, but sometimes it needs replacement.
• Low fuel pressure: A failing fuel pump or clogged filter can cause low pressure, affecting all cylinders. 

3. Mechanical problems

• Burnt exhaust valve: This can cause a significant compression leak in the cylinder. 
  • Troubleshooting: A compression test can help diagnose this issue. Repairing or replacing the valve is necessary. 
• Leaking head gasket: This is less common but can cause a misfire. 
• Other internal engine issues: Problems like a bad valve or other mechanical issues can lead to a misfire. 

How to diagnose further

• Check engine light: The “Check Engine” light will be illuminated. You’ll need a diagnostic scanner to read the specific code, which is P0304 for cylinder 4. 
• Symptoms: Expect rough idling, loss of power, reduced fuel efficiency, and hesitation during acceleration. 
• Diagnostic steps:
  1. Read the trouble code with a scanner. 
  2. Visually inspect the spark plug in cylinder 4 for wear or fouling. 
  3. Swap the ignition coil from cylinder 4 with another cylinder and drive the car to see if the misfire code follows the coil. 
  4. If the misfire persists, consider checking the fuel injector and performing a compression test to rule out mechanical issues. 

How serious is a cylinder 4 misfire?

A cylinder 4 misfire is serious because it can cause immediate performance issues like rough idling and loss of power, and if left unaddressed, it can lead to costly damage to the engine and catalytic converter. It is recommended to have the vehicle diagnosed and repaired as soon as possible to avoid more significant and expensive problems. 
Short-term consequences

• Rough engine operation: The car may shake, idle roughly, or hesitate when accelerating. 
• Poor performance: You will experience a noticeable loss of power and poor acceleration, which can be dangerous when merging or passing. 
• Reduced fuel efficiency: The engine burns fuel inefficiently, leading to lower gas mileage. 
• Increased emissions: The vehicle will produce more harmful emissions. 

Potential long-term damage 

• Catalytic converter damage: Unburned fuel can enter the exhaust system and ignite, causing extreme heat that can melt and clog the catalytic converter, a very expensive part to replace. 
• Engine damage: Repeated misfires can stress engine components like pistons and valves, leading to severe damage over time. 
• Engine failure: If left unresolved, a misfire can eventually lead to catastrophic engine failure. 

What you should do

• Do not ignore it: Do not assume the problem will fix itself. 
• Drive with caution: Avoid driving the vehicle if possible. If you must drive, avoid hard acceleration and high speeds. 
• Get it diagnosed: Take the vehicle to a mechanic to properly diagnose the cause, which could be anything from a faulty spark plug to a more serious fuel or engine problem. 

How much does it cost to fix a cylinder 4 misfire?

The cost to fix a cylinder 4 misfire can range from less than $100 to over $2,000, depending on the cause, which could be a simple and cheap fix like a spark plug or a more expensive one like a timing chain. Common causes include bad spark plugs, faulty ignition coils, fuel injector problems, or issues with the air/fuel mixture or timing belt/chain. 
Potential causes and costs

• Spark Plugs: Replacing a spark plug is one of the cheapest and most common fixes, costing between $80 and $320. 
• Ignition Coil: A failing ignition coil is another common issue, with replacement costs ranging from $150 to $800. 
• Fuel Injector: Cleaning a dirty fuel injector might be inexpensive, but a full replacement could cost hundreds of dollars. 
• Vacuum Leaks: Repairing a vacuum leak can be cheap if it’s just a hose, but if it involves replacing a gasket, it could be more. 
• Timing Belt/Chain: Replacing a timing belt costs between $300 and $500, while a timing chain can cost up to $2,000. 

What you should do

• Get a diagnosis: The first step is to have a professional diagnose the specific cause of the misfire to avoid paying for unnecessary repairs. 
• Address it quickly: Driving with a misfire can cause further damage to other components like the catalytic converter, leading to much higher repair bills down the line. 

How to fix engine code cylinder 4 misfire?

Your best bet is to take the ignition coil out of cylinder 4 and swap it with cylinder 1 then take the spark plug from cylinder 4 and swap it with cylinder 2, clear the fault codes, drive the car and see if the misfire follows the spark plug or the ignition coil.