Operation Nissan Murano the second generation (Z51 body) is associated with a number of service features, especially when it comes to power units of the VQ family. Engine VQ35DE The 3.5-liter engine installed on this model is characterized by high dynamics, but requires an impeccable condition of the ignition system. Ignoring maintenance schedules can lead to unstable engine operation at idle and increased fuel consumption.
Many owners are faced with the need to replace ignition elements much earlier than scheduled maintenance, especially in aggressive city driving conditions or when using low-quality fuel. Timely diagnostics and correct installation of new components can return the car to the factory characteristics of gas pedal response and smoothness. In this article we will analyze in detail how to correctly perform this procedure with your own hands.
The replacement process is not overly complicated, but it has its own technical nuances that must be taken into account. Incorrect tightening torque or damage to the ceramic insulator during dismantling can lead to serious consequences. It is important to follow the procedure and use only tools recommended by the manufacturer for working in the confined space of the engine compartment.
Service intervals and signs of wear of the ignition system
Factory regulations for Nissan Murano Z51 requires replacement of spark plugs every 100,000 kilometers if iridium cells are used. However, actual operation often makes its own adjustments, reducing this interval to 60,000 - 80,000 km. The quality of fuel in our regions rarely meets ideal standards, which accelerates wear of the electrodes and carbon formation.
You can understand that it is time to service the engine by a number of indirect signs that appear in the dynamics of the car. If you notice that the gas pedal begins to respond sluggishly, and when pressed sharply the engine begins to twitch, this is the first signal of problems with the spark. Also a characteristic symptom is vibration of the power unit at idle, which is felt through the steering wheel and seats.
- 📉 Increased fuel consumption for no apparent reason and changes in driving style.
- ⚡ Misfire of the mixture, recorded by a diagnostic scanner (errors P0300-P0306).
- 🌡️ Difficulty starting the engine in the cold season with a working battery.
- 💨 Unstable operation in transient modes, accompanied by jerks.
Ignoring these symptoms can lead to failure of the ignition coils. In the VQ35DE system, each spark plug has its own individual coil, and running on a dead cylinder overloads adjacent elements. Diagnostics must be carried out comprehensively to eliminate errors in 判断 (judgment) about the condition of the motor.
⚠️ Attention: If you notice a misfire error on the scanner, do not delay visiting the service center or replacing it yourself. Running the engine with a misfire can lead to overheating and destruction of the exhaust gas catalytic converter, the replacement of which will cost several times more than a set of spark plugs.
Choosing the right candles and the necessary tools
For engine VQ35DE It is critical to use plugs with the correct heat rating and gap. Car manufacturers recommend original spark plugs Nissan with article number 22401-ED01A or their full analogues from leading manufacturers. The use of cheap analogues with nickel plating instead of iridium will lead to the need for replacement after 20,000 km.
The key parameters are the length of the threaded part and the design of the insulator. Plugs that are too long can hit the piston, leading to fatal engine destruction, while plugs that are too short will not ensure reliable ignition of the mixture in the combustion chamber. It is also necessary to check the condition of the o-ring, which ensures the tightness of the combustion chamber.
- 🔧 21 mm (usually 5/8 inch) spark plug wrench with long head and extension.
- 📏 Torque wrench for precise tightening with a torque of 11-13 Nm.
- 💨 Blow gun or compressor for cleaning wells from dust.
- 🔦 A powerful flashlight for visually monitoring the condition of old candles.
Pay special attention to the cleanliness of your work area. Before starting work, you must thoroughly clean the area around the spark plug wells. Dust and dirt that gets into the cylinder when unscrewing the spark plug can cause scuffing of the cylinder walls and failure of the piston group. Use compressed air or a soft brush to remove dirt.
⚠️ Attention: Never try to unscrew the spark plugs while they are hot. The engine must cool completely to ambient temperature, otherwise the risk of thread failure in the aluminum cylinder head increases many times due to the difference in thermal expansion coefficients.
Preparing the workplace and dismantling attachments
Access to candles Nissan Murano The Z51 is hampered by the design of the intake manifold and the placement of the ignition coils. The upper cylinders (1, 3, 5) are relatively easy to access, while the lower ones (2, 4, 6) require removal of the plastic decorative cover and, in some cases, partial dismantling of the intake tract. Be prepared for the job to take longer than with conventional inline engines.
You must first disconnect the negative terminal of the battery to prevent an accidental short circuit. Next, remove the plastic decorative engine cover by gently pulling it up, as it is secured with plastic clips. After this, disconnect the power connectors from the ignition coils and unscrew the bolts securing them.
- Every 40,000 km
- Every 60,000 km
- Every 100,000 km
- According to engine condition
Remove the ignition coils vertically, being careful not to damage the plastic housing and rubber tip. If the coil is tight, you can gently wiggle it, but do not use excessive force. Inspect the condition of the rubber covers of the coils - if they are cracked, it is better to replace them to avoid spark breakdown to ground.
☑️ Preparation for dismantling
Now you can start unscrewing the candles themselves. Use a spark plug wrench with a magnetic tip or rubber insert to hold the spark plug when removing it from the well. If the spark plug is stuck, do not try to unscrew it with a jerk - use penetrating lubricant, but be extremely careful that it does not get inside the cylinder.
Technology for installing new spark plugs and final assembly
Installing new spark plugs requires pinpoint precision. Before screwing in, be sure to check the gap between the electrodes, although on iridium spark plugs it usually does not require adjustment. Screw the new spark plug into the well by hand until it stops so as not to distort the thread. This is the most crucial moment, since a cut thread in an aluminum cylinder head is a serious problem that requires repair.
After hand tightening, use a torque wrench for final tightening. The tightening torque for spark plugs on the VQ35DE engine is 11-13 Nm. If you don't have a torque wrench, use the 1/8-1/4 turn rule after the stop, but this is less reliable. Padding can lead to deformation of the spark plug body and problems with heat dissipation, and insufficient exhaustion can lead to burnout of the o-ring.
Reinstall the ignition coils, making sure they are seated tightly on the spark plugs. Insert the connectors until you hear a characteristic click and tighten the coil mounting bolts. Replace the decorative plastic engine cover, making sure all the fasteners are in place. Connect the negative terminal of the battery.
What to do if the spark plug won't come out?
If the spark plug cannot be unscrewed, do not use brute force. Try heating the cylinder head around the spark plug with a heat gun to expand the metal, and try again. You can apply a little penetrating lubricant (WD-40) to the threads, but be careful not to get it into the cylinder. As a last resort, use a special extractor, but this is a risky operation.
After assembly, you need to start the engine and check its operation. Start the engine and let it idle. Listen to the sound of work - it should be smooth, without gaps or vibrations. If the engine is unstable, check the connection of the coils and the correct installation of the spark plugs.
Using a torque wrench when tightening spark plugs is not a whim, but a necessity that guarantees the tightness of the combustion chamber and the safety of the threads in the cylinder head.
Analysis of the condition of old spark plugs and engine diagnostics
Removed old spark plugs are an excellent diagnostic tool that tells you about the condition of the engine. The color of soot on the insulator can say a lot about the quality of combustion of the fuel mixture. The white or light brown color of the insulator indicates normal engine operation and the correct composition of the mixture.
If you see black, dry and fluffy carbon deposits, this indicates an over-rich mixture or problems with the ignition system. Wet black carbon often indicates oil has entered the combustion chamber, which may be a sign of worn valve stem seals or piston rings. Oil deposits on the electrodes require immediate intervention in the engine.
| Electrode condition | Possible reason | Recommended Actions |
|---|---|---|
| Black dry soot | Over-enriched mixture, clogged filters | Check the air filter, injectors |
| Oily coating | Worn piston group or caps | Compression, engine repair |
| Light gray color | Normal Operation | Install new spark plugs |
| Molten electrode | Overheating, advance angle too early | Check heat rating, sensors |
White carbon deposits with metallic flecks may indicate the use of low-quality fuel or engine overheating. If you find traces of oil on several spark plugs in a row, this is a serious reason for in-depth engine diagnostics, as the problem may be systemic. Ignoring such symptoms will lead to major repairs in the future.
Store one of the old spark plugs in a sealed bag with the date it was replaced. This will help with subsequent diagnostics if the owner wants to show the technician what the spark plugs looked like after a certain mileage.
Common mistakes when servicing the ignition system
Even experienced craftsmen sometimes make mistakes when replacing candles with Nissan Murano Z51. One of the most common problems is damage to the ceramic insulator when unscrewing. If the insulator cracks, a spark will be sent to the housing and the cylinder will stop working, even if a new spark plug is installed.
Another mistake is incorrect installation of the O-ring. If the ring is twisted or lost, this will lead to air leaks and a leak. They also often forget to check the condition of the ignition coils for cracks or breakdowns. Old coils may not give a spark to a new spark plug, and the owner will look for a problem where there is none.
- 🚫 Using extensions of the wrong length, which makes access difficult and increases the risk of chipping.
- 🚫 Lubricating the candle thread with graphite grease (only light lubrication with copper paste is allowed).
- 🚫 Ignoring the tightening torque and relying on the “feeling of the hand.”
- 🚫 An attempt to use candles with a deliberately different heat number.
Make sure all connectors are fully inserted and latched. If the error does not disappear after replacing the spark plugs, the problem may lie in the ignition coil or wiring. Diagnostics must be consistent and methodical.
⚠️ Attention: Do not try to clean old candles with sandblaster or chemicals for reuse. Iridium coating is microscopically thick, and any cleaning will destroy it, making the spark plug unsuitable for further use.
FAQ: Answers to frequently asked questions from owners
Owners Nissan Murano Often asked questions related to the nuances of servicing the ignition system. Below are answers to the most popular ones that will help you avoid unnecessary costs and problems.
Is it possible to replace spark plugs on a VQ35DE engine without removing the intake manifold?
In most cases, to replace spark plugs on the rear cylinders (2, 4, 6), it is enough to remove the decorative cover and move the hoses. However, if you have an additional air filter or other modifications installed, you may need to partially remove the intake tract. The original does not require complete removal of the manifold.
Which spark plugs are better: original Nissan or NGK/Denso?
Genuine Nissan spark plugs for the Murano Z51 are often manufactured by NGK or Denso and have the same characteristics. You can safely buy NGK or Denso spark plugs that match the catalog number, which is often cheaper than Nissan branded packaging.
Do I need to change the ignition coils along with the spark plugs?
If the coils are working properly and have no visible damage, there is no need to replace them. However, if you see cracks in the housing or spark failure, replacing the coils is highly recommended, as the old coils may not be able to withstand the stress of the new spark plugs.
How often should I check the gap on iridium spark plugs?
The gap on iridium spark plugs does not require regular checking and adjustment. It is fixed at the factory and is maintained throughout its entire service life. It is not recommended to adjust it yourself, as there is a risk of damaging the thin iridium electrode.
What happens if you overtighten a candle?
Over-tightening can lead to deformation of the spark plug body, disruption of heat dissipation, and even breakage of the threads in the cylinder head. This will require an expensive repair using a socket insert or replacing the cylinder head.