Error P0304 Nissan: Diagnosis and elimination of misfire in the 4th cylinder

When the Check Engine light comes on on the dashboard and the scanner produces a code P0304, car owners Nissan often face a lack of understanding of the seriousness of the situation. This code indicates a misfire in the fourth cylinder of the engine. Ignoring such a problem can lead to failure of the expensive catalyst and a serious drop in the power of the unit.

Unlike general errors indicating problems with the entire ignition system, P0304 localizes the fault to one specific point. This greatly simplifies the search for the cause, but requires careful attention to detail. You need not just to replace the spark plug, but to understand why the combustion process of the fuel-air mixture is disrupted in this particular cylinder.

Engine management system Nissan uses a crankshaft position sensor to monitor rotation speed. If a misfire occurs in one of the cylinders, the shaft rotation speed drops briefly, and the ECU records this event. When the frequency of such omissions exceeds the set threshold, the malfunction indicator lights up and a code is written into memory. P0304.

The main causes of misfire in the 4th cylinder

Nature of the error P0304 on cars Nissan Qashqai or X-Trail It usually comes down to three main factors: no spark, no fuel, or low compression. Most often, the problem lies in the ignition system, since these components are subject to the greatest wear and tear when used in our conditions.

Spark plugs are the weakest link in the chain. Over time, the electrodes burn out, the gap increases, and the spark becomes too weak to ignite the mixture. In the case of the fourth cylinder, which is often located closer to the exhaust manifold, the spark plugs may overheat faster than the others, which accelerates their degradation and leads to misfire.

The second most popular culprit is the ignition coil (coil module). Many MR and QR series engines use an individual ignition system, where each spark plug has its own coil. If the coil insulation breaks through or the winding burns out, the spark to the fourth cylinder stops flowing altogether. This is a common problem for models Nissan Teana and Almera.

Problems with the fuel system should not be ruled out. A clogged or faulty injector may not deliver enough fuel to the cylinder or may not spray fuel correctly, creating an insoluble mixture. Vacuum leaks are also possible, causing excess air to enter the combustion chamber, leaning the mixture and making ignition impossible.

• 💥 Wear or carbon deposits on the spark plugs in the 4th cylinder.
• ⚡ Insulation breakdown or failure of the ignition coil.
• 🔫 The nozzle is malfunctioning or its electrical contact is broken.
• 🌪️ Suction of unaccounted air through cracks in pipes or gaskets.

Diagnostics of the ignition and fuel system

Before you run to the store for new spare parts, you need to conduct a thorough diagnosis. The simplest and most effective method is to rearrange the components. Take the ignition coil or spark plug from the fourth cylinder and install it on the adjacent cylinder (for example, the third). If after this manipulation the error changes to P0303, then the problem is definitely in the part that you rearranged.

If the error remains P0304, which means the reason is not in the coil or spark plug. The injector needs to be checked. To do this, you can listen to the engine with a stethoscope or replace the injector from the 4th cylinder to another. It is also worth checking the electrical connectors: oxidation of the contacts or poor contact in the block may interrupt the signal supply to the coil.

It is important to check the air supply system as well. Carefully inspect the intake manifold, especially around the fourth cylinder. Cracks in the plastic or loss of gasket seal can lead to air leaks. Use a fogger or aerosol cleaner (carbcleaner) method to find leaks, but do so with caution and safety precautions.

Engine mechanical problems and compression

If the electrical part and injection system are working properly, and the error P0304 continues to burn, the problem may be deeper - in the mechanics of the engine. Low compression in the fourth cylinder will not allow the mixture to burn properly, even with an ideal spark and fuel. This may be caused by worn piston rings or valve problems.

This is especially true for cars with high mileage. Worn piston rings cause the pressure in the cylinder to drop and gases to leak into the crankcase. It is also possible that the valve burns out or the thermal gap is violated. In such cases, simply replacing the spark plugs will not be enough; a major overhaul or replacement of the cylinder head will be required.

For an accurate diagnosis, it is necessary to measure the compression. Use a compression gauge by screwing it into the spark plug hole of the fourth cylinder. Compare readings with results for other cylinders. A difference of more than 10-15% from the average value is already an alarming signal, indicating the need for serious intervention in the engine design.

⚠️ Attention: If you find that the compression in the 4th cylinder is significantly lower than in the others, do not try to solve the problem by adding additives to the oil. This is only a temporary measure that may worsen the situation with the catalyst.

Sometimes the problem lies in the phase shifters or the gas distribution system. If the timing belt or chain has stretched and jumped one tooth, this will disrupt the injection and ignition phases. As a result, the mixture may simply not have time to burn or burn out in the exhaust manifold. Check the timing marks, especially if the car has significant mileage and the chain has not been replaced.

• 📉 Low compression due to wear of piston rings.
• 🔥 Burnout of the exhaust or intake valve in the 4th cylinder.
• ⛓️ Timing chain stretching or marks jumping.
• 🔧 Incorrectly adjusted valve thermal clearances.

Step-by-step instructions for resolving the error

You should always start repairs with the simplest and cheapest. The first step is to replace the spark plugs. Use original candles Nissan or high-quality analogues from trusted brands such as NGK or Denso. Make sure the clearance is within factory specifications for your engine.

After replacing the spark plugs, check the condition of the coils. If they show signs of breakdown (black stripes or carbon deposits), they must be replaced. When installing new coils, be sure to apply dielectric grease deep into the block to prevent breakdown of the housing and ensure reliable contact.

If the problem is not resolved, the next step is to check the fuel injectors. They can be removed, washed on the stand and checked for spraying. Also check the injector resistance with a multimeter. It must be in the range specified in the technical documentation (usually 12-16 Ohms for injection systems).

Lastly, if all of the above does not help, you should start diagnosing the mechanical part. This is the most labor-intensive process and requires disassembling the engine. Check the condition of the cylinder head gasket, condition of the pistons and valves. The head may need to be resurfaced or the valves replaced.

After completing all the work, be sure to reset the errors using the OBDII scanner. Start the engine and let it run in warm-up mode. Take a test drive, simulating different driving modes: acceleration, braking, driving uphill. Make sure the error P0304 does not return and the engine runs smoothly, without vibrations or failures.

⚠️ Attention: If there is an error P0304 accompanied by severe engine shaking, stop immediately and turn off the engine. Driving a rough engine can cause permanent damage to the catalytic converter due to unburned fuel entering the exhaust system.

Table of Common Causes and Probabilities

For clarity, we provide statistics on the frequency of problems that lead to the code P0304 on cars Nissan. Understanding probability will help you focus on the most likely causes when making a diagnosis.

Cause	Probability	Difficulty of repair	Approximate cost
Faulty spark plug	45%	Low	Low
Ignition coil failure	30%	Average	Average
Injector malfunction	15%	Average	High
Compression problems (mechanical)	8%	High	Very high
Air/vacuum leak	2%	Low	Low

What is coil swapping and why is it needed?

The permutation method allows you to accurately locate the faulty part without complex equipment. If the error changes from P0304 to P0303 after moving the coil from the 4th to the 3rd cylinder, then the coil is faulty. If the error remains P0304, the problem is not in the coil.

Prevention and operating tips

To avoid the error reappearing P0304, it is necessary to comply with the maintenance regulations. Change spark plugs every 30-40 thousand kilometers, even if they look normal. The electrodes burn out gradually, and visual inspection does not always allow one to assess the actual state of the gap.

Use only high quality gasoline. Low-quality fuel with a large amount of impurities can quickly coke the injectors and lead to uneven combustion. For engines Nissan with direct injection (GDI) this is especially critical, as they are more sensitive to fuel quality.

Regularly check the condition of high-voltage wires (if your equipment includes them) and connectors. Oxidation of contacts can lead to unstable operation of the ignition system. Periodically treat connectors with special aerosols to protect them from moisture and corrosion.

Monitor the condition of the crankcase ventilation system (PCV valve). If it is clogged, crankcase pressure increases, which can force oil into the intake manifold. Oil gets on the spark plugs and coils, causing misfires and subsequent errors. P0304.

• ⏱️ Change candles strictly according to the regulations, do not wait for them to completely fail.
• ⛽ Refuel only at proven gas stations with high-quality fuel.
• 🧹 Clean the throttle body and intake manifold regularly.
• 🔍 Monitor the operation of the crankcase ventilation system and PCV valve.

FAQ: Frequently asked questions

Is it possible to drive with P0304?

Short term - yes, but with caution. If the engine shakes a lot, it's better not to take risks. Long-term operation with misfires can lead to overheating of the catalyst and its destruction, which will cost much more than repairing the ignition system.

How quickly will the error disappear after replacing the spark plug?

The error itself may not disappear immediately. The Nissan ECU usually requires a certain driving cycle (usually several drives in different modes) to ensure that the problem is resolved. If the error does not clear automatically, you can use a diagnostic scanner to force the codes to reset.

Does the quality of gasoline affect the P0304 error code?

Yes, fuel quality directly affects the combustion process. Low-octane gasoline or fuel with impurities can cause knocking and misfire, especially in older engines or under high loads. This is a common cause of temporary omissions.

Do I need to change all the coils at once?

Officially, no, it’s enough to replace the faulty one. However, if one coil fails, the rest may not work for long, since they are of the same age and operating conditions. Many experts recommend replacing them with a kit for reliability, especially if the car has high mileage.

What should I do if the P0304 code returns after replacing the spark plug?

If replacing the spark plug does not help, the problem is most likely in the ignition coil, injector or engine mechanical part (compression). Swap the coil to an adjacent cylinder to check. If the error has not moved, check the injector and compression.