The appearance of the code P0304 on the car dashboard Nissan Qashqai always becomes a signal to the owner about serious problems with the engine. This diagnostic code indicates that the electronic control unit has detected systematic misfires of the fuel-air mixture in the fourth cylinder. Ignoring such a signal can lead not only to loss of dynamics and increased fuel consumption, but also to irreversible damage to the catalytic converter due to unburned fuel entering the exhaust system.
Fourth cylinder in in-line engines Nissan often susceptible to specific problems due to its location and design features of the ignition system. Crossover owners are faced with the fact that the engine begins to run unevenly, vibrations appear at idle, and during acceleration there is a significant loss of power. Timely diagnosis and identification of the root cause is the only way to avoid costly repairs and return the car to factory specifications.
Causes of misfire in the fourth cylinder
The main reason for the error P0304 is a violation of the fuel combustion process inside the combustion chamber of the fourth cylinder. This can happen for three fundamental reasons: lack of spark, fuel supply problems or low compression. In most cases on the engine MR20DE, which is installed on Nissan Qashqai, the culprits are the ignition system components, as they are subject to wear at high temperatures.
The second most common cause is a faulty fuel injector. If the nozzle is clogged, clogged, or has an electrical break, the mixture will not be delivered at the correct volume or sprayed properly. It is also worth checking the integrity of high-voltage wires and spark plugs, which lose their properties over time. Often the problem occurs due to air leaks through the intake manifold gasket in the area of ββthe fourth cylinder, which leans the mixture and prevents normal ignition.
- π₯ Malfunction of the ignition coil or spark plugs, requiring immediate replacement
- β½ Clogged or electrical failure of fuel injector No. 4
- π¨ Suction of unaccounted air through the intake tract gaskets
- π§ Mechanical damage to the piston group or valves
Diagnostics of the ignition system and spark plugs
The first step in fixing the error is P0304 There should be a visual and instrumental check of the spark plugs. You need to remove the ignition coil located directly above the fourth cylinder and remove the spark plug. Carefully inspect the electrode: the presence of carbon deposits, oily deposits or a melted gap will directly indicate the nature of the problem. If the spark plug looks like new and the problem persists, it may be the ignition coil.
It is important to perform a component swap test to rule out false diagnoses. Swap the ignition coil from the fourth cylinder to the adjacent one (for example, to the third) and clean the spark plugs. After this, reset the error through the diagnostic scanner and drive the car. If the error code has moved to another cylinder (for example, it becomes P0303), then the problem was in the coil. If the error remains P0304, which means the fault lies deeper - in the injector, compression or wiring.
- π Inspect the spark plug gap and the color of the insulator for breakdowns
- π Check the resistance of the ignition coil with a multimeter
- π Use the permutation method to accurately localize the defect
Checking the fuel system and injectors
If the ignition system has been checked and is working properly, the next step is diagnosing the fuel system. The fuel injector in the fourth cylinder may not work properly due to contamination of the injector or poor electrical contact. It is necessary to check the resistance of the injector winding and the presence of a control pulse from the engine control unit. The absence of a pulse may indicate a wire break in the harness or a malfunction of the ECU itself.
Particular attention should be paid to the cleanliness of the injectors. Long-term operation on low-quality fuel leads to the formation of varnish deposits that interfere with normal atomization. To check, you can use a stethoscope or simply listen to the operation of the injectors by ear - they should make a clear clicking sound when the engine is running. It is also recommended to check the pressure in the fuel rail, since a drop in it can cause a lean mixture in all cylinders, but this will be more pronounced in the problematic fourth.
β οΈ Attention: When checking the fuel system, observe fire safety measures. The fuel rail is under high pressure, so the hoses should only be disconnected after the pressure in the system has been relieved.
- Ignition coil
- Candles
- nozzle
- Air leak
Mechanical failure and compression
Once the electrical and fuel components have been eliminated, all that remains is to check the mechanical part of the engine. Low compression in the fourth cylinder can be caused by stuck piston rings, burnt valves, or worn valve seats. For an accurate diagnosis, it is necessary to conduct a compression test in all cylinders. If in the fourth cylinder the indicator is significantly lower than in the others (the difference is more than 10-15%), then the problem is mechanical in nature and requires intervention in the engine.
In engines Nissan MR20 Often there is a problem with timing chain stretching or incorrect operation of phase shifters, which can also lead to misfire in a particular cylinder. If compression is normal, it is worth checking the intake manifold for leaks. Cracks or leaks in the area of ββthe fourth cylinder lead to air leaks, which leans the mixture. Using an aerosol can of carburetor cleaner sprayed around the gaskets while the engine is running will help identify the location of the leak by changes in rpm.
βοΈ Checking the mechanical part of the engine
Step-by-step instructions for resolving the error
To resolve the error yourself P0304 it is necessary to follow a clear algorithm of actions. Start by visually inspecting the wiring harness leading to the cylinder 4 ignition coil and injector. Check for signs of overheating, contact oxidation or mechanical damage to the insulation. Often the problem is solved by simply cleaning the contacts or restoring the integrity of the wire.
Next, replace the spark plugs with new ones recommended by the manufacturer. If the problem persists, replace the ignition coil. If these measures do not help, a check and possible replacement of the fuel injector will be required. If the error returns after replacing the injector, you will have to carry out compression diagnostics and check the mechanical components of the engine.
β οΈ Warning: Do not try to resolve the P0304 code by simply resetting codes without finding the cause. The reappearance of the error will confirm the presence of a malfunction, and constant driving with misfires can destroy the catalyst, the repair of which is expensive.
What to do if error P0304 appears only under load?
If the error occurs only when the gas is pressed sharply, this may indicate a weak spark discharge that cannot penetrate the increased resistance in the pressurized cylinder. Try replacing the ignition coil with a known good one or checking the spark plug gap; it may have increased over time.
Table of Symptoms and Probable Causes
Below is a summary table that will help you quickly navigate the causes of the error and choose the right diagnostic path. Each symptom is associated with the most likely cause and recommended action.
| Symptom | Probable Cause | Recommended Action |
|---|---|---|
| The engine is rough at idle, the vibration is strong | Ignition coil malfunction | Replacing the coil with a new component |
| Skips only during acceleration | Spark plugs or weak gap | Replacing a set of spark plugs |
| Increased fuel consumption, smell of gasoline | Leaking fuel injector | Checking the tightness and replacing the nozzle |
| Reduced compression, engine noise | Mechanical wear of the cylinder-piston group | Engine overhaul |
| Error P0304 + P0171 (lean mixture) | Air leak in the intake manifold | Replacing intake manifold gaskets |
Before starting any engine diagnostic work, be sure to disconnect the negative terminal of the battery to avoid a short circuit when disconnecting the connectors.
Prevention and recommendations for use
To avoid the error reappearing P0304 on your Nissan Qashqai, you must adhere to a regular maintenance schedule. Spark plugs should be changed every 30-40 thousand kilometers, and coils - at the first signs of unstable operation. Using quality fuel with the correct octane rating also plays a critical role in maintaining the life of the injectors and combustion chamber.
Do not neglect the use of flushing fluids for the fuel system if you often drive your car in urban environments with frequent traffic jams. This will help keep the injector nozzles clean and ensure even mixture formation. It is also important to monitor the condition of the air filter, as its contamination can lead to a lean mixture and misfire.
β οΈ Attention: Ignoring error P0304 over 500 km can lead to complete failure of the catalytic converter, the cost of replacing which exceeds the cost of repairing the ignition system by 5-7 times.
FAQ: Frequently asked questions
Is it possible to drive with P0304?
It is strictly not recommended to drive with this error. Misfires result in unburned fuel entering the exhaust system, which overheats and destroys the catalyst. In addition, unburned fuel washes oil from the cylinder walls, accelerating wear of the piston group.
How much does it cost to repair error code P0304 on a Nissan Qashqai?
The cost depends on the reason. Replacing a spark plug is inexpensive, replacing a coil is average, but replacing an injector or repairing an engine will cost much more. Focus on prices ranging from 1,500 rubles per candle to 25,000+ rubles for major repairs.
Why does the error only appear when it is cold?
When cold, the gaps in the metal are larger and the oil viscosity is higher. If there is a microcrack in the gasket or wear on the rings, on a hot engine it can be βhealedβ by the expansion of the metal. Also, when cold, ignition coils most often fail due to condensation or aging insulation.
Do I need to change all the coils at once?
If you find one faulty coil, and the others already have a lot of mileage, it is wise to replace them all as a set. Coils wear out at about the same rate, and replacing one may not solve the problem for long if the others are about to fail.
How to reset an error after repair?
After troubleshooting, use the OBD2 diagnostic scanner to reset the error codes. If there is no scanner, you can disconnect the battery for 10-15 minutes, but this will also reset other car settings. It is best to use professional equipment.