Checking the condition and replacing spark plugs (Nissan Maxima A32)

Tools needed when replacing spark plugs

Note: If the original spark plugs are to be reinstalled on the engine after checking their condition, they must be screwed strictly into the previous cylinders, and mark them accordingly.

1. In most cases, replacing spark plugs requires a special spark plug head (with elastic liner inside) complete with a ratchet drive, as well as a set of extensions for the key drive and a device for checking and adjusting the interelectrode gaps. A special tool is also available for safely disconnecting the high-voltage wire tips from the spark plug tails, although its use is not strictly required. Using a torque wrench will allow you to achieve the correct tightening force for the spark plugs.

2. It is best to keep a set of replacement spark plugs with the correct gap adjustment in your vehicle at all times. When purchasing new spark plugs, make sure that they meet the parameters of your vehicle's engine. The necessary information is provided in the Specifications for this Chapter and on the VECI label attached under the hood (in case of discrepancies, preference should be given to information from VECI).

3. Start removing the spark plugs only after the engine has completely cooled down. In order not to waste time, use the pause to check the condition of the replacement kit.

4. The spark plug gap is checked by inserting the appropriate feeler gauge into it and must meet the requirements specified on the VECI label (see also Specifications). The feeler gauge should slide between the side and central electrodes of the spark plug with slight resistance. The gap can be adjusted using a special device, usually included in the measuring device - bend the side electrode of the spark plug accordingly.




5. If the side electrode is not positioned exactly above the central one, adjust its position accordingly. Make sure there are no cracks or other damage in the porcelain insulator of the spark plug. The presence of any kind of defects in the insulator is unacceptable.



6. On 1993 and 1994 models, to avoid confusion during assembly, mark the spark plug wires before disconnecting. Disconnect the spark plug wire from the spark plug of the first cylinder. Pull only by the tip, and under no circumstances by the wire! It would be wise to use a special tool.



7. If you have a source of compressed air on hand, use it to remove debris from the spark plug niches of the engine (a regular bicycle pump would be just as good for this purpose).

Caution! When using compressed air, do not forget to wear safety glasses!

8. Remove the spark plugs.

Note: To avoid confusion with the wiring/coil connections, replace each spark plug one at a time.

9. Compare the removed spark plug with the identification card below, which will allow you to qualitatively assess the overall condition of the engine.

Coal deposits

Symptoms: The presence of soot indicates an over-rich fuel-air mixture or weak spark intensity. Causes misfires, difficult starting and leads to unstable engine operation.

Recommendations: Check if the air cleaner is clogged, if the fuel level in the float chamber is too high, if the air damper is stuck and if the contacts are too worn. Try using spark plugs with a longer insulator, which increases resistance to contamination.

Normal condition of the candle

Symptoms: Grey-brown color and slight wear of the electrodes. The glow number of the spark plugs corresponds to the type of engine and its general condition.

Recommendations: When replacing spark plugs, install spark plugs of the same type.

Oiling

Symptoms: Oiling of the spark plug is caused by worn out oil deflector caps. Oil gets into the combustion chamber through worn valve guides or piston rings. Causes misfires, difficult starting and leads to unstable engine operation.

Recommendations: Perform mechanical repairs and replace spark plugs.

Ash formation

Symptoms: Soft, brownish deposits on one or both spark plug electrodes. These are caused by oil and/or fuel additives. Excessive buildup can insulate the electrodes and cause misfires and rough running under acceleration.

Recommendations: If deposits accumulate quickly, replace the oil seals, which will prevent oil from entering the combustion chambers. Try changing the fuel brand.

Overheat

Symptoms: Porous, white insulator, erosion of electrodes and absence of any deposits. Leads to a reduction in spark plug life.

Recommendations: Check that the installed spark plugs are of the correct heat range, that the ignition timing is set correctly, that the fuel/air mixture is not too lean, that there are no vacuum leaks in the intake manifold and that the valves are not stuck. Also check the coolant level and that the radiator is not clogged.

Wear

Symptoms: Rounding of the electrodes with a small accumulation of deposits at the working end. Color is normal. Causes difficulty starting the engine in cold, wet weather and increased fuel consumption.

Recommendations: Replace the spark plugs with new ones of the same type.

Too early ignition

Symptoms: The electrodes are melted. The insulator is white, but may also be contaminated due to misfiring or foreign particles entering the combustion chambers. May cause engine failure.

Recommendations: Check the glow number of the installed spark plugs, the ignition timing, and the quality of the mixture (isn't it too poor?), whether the cooling system is clogged and whether the lubrication system is functioning normally.

Detonation

Symptoms: Insulators may be chipped or cracked. Insulator damage may also result from improper spark plug gap adjustment. Piston damage may result.

Conductive gloss

Symptoms: The insulator has a yellowish color and a polished appearance. Indicates a sudden increase in temperature in the combustion chambers during sharp acceleration. Normal deposits melt, acquiring the appearance of a varnish coating. Leads to misfires at high speeds.

Recommendations: Change the spark plugs (cooler, while maintaining the same driving style).

Splashing

Symptoms: After a long period of misfire, deposits may become loose while the combustion chamber remains at operating temperature. At high speeds, deposits flake off the piston and stick to the hot insulator, causing misfires.

Recommendations: Replace the spark plugs or clean and reinstall the old ones.

Short circuit of electrodes

Symptoms: Combustion waste gets into the interelectrode space. Solid deposits accumulate, forming a bridge between the electrodes. Leads to ignition failure in the cylinder.

Recommendations: Remove deposits from the interelectrode space.

Mechanical damage

[Information copied from the website nissanbook.ru]

Symptoms: Can be caused by foreign material entering the combustion chamber or by the piston hitting a spark plug that is too long. Leads to cylinder failure and piston damage.

Recommendations: Remove foreign particles from the engine and/or replace

10. Before screwing in the new spark plugs, lightly lubricate their threads with anti-seize sealant. Manually thread one of the new spark plugs into the corresponding hole in the engine. After making sure that the spark plug is not distorted in the thread, tighten it to the required force (if you have a torque wrench at hand). To make the spark plug fitting procedure easier, pull a piece of flexible fuel hose onto its tail. This eliminates the possibility of thread stripping, since the slightest biting will simply cause the hose to start turning.


11. On 1993 and 1994 models, the high-voltage wire is connected to the spark plug by rotating and reciprocating the tip of the wire - the tip should fit snugly onto the spark plug stem. The individual spark plug coils used on 1995 and later models are equipped with their own short spark plug wires - when installing, simply fit the assembly snugly onto your spark plug without rotating it on the stem.

12. Repeat the procedure for the remaining spark plugs, performing each step in turn to avoid disturbing the firing order.