Note. If the original spark plugs are re-installed on the engine after checking the condition, they must be screwed strictly into the previous cylinders - make the appropriate marking.
Tools needed when changing spark plugs
- 1. Candle head - Equipped with a special soft insert, which excludes the possibility of accidental damage to the porcelain insulator when the candle is turned inside out.
- 2. Torque wrench - Although not mandatory, it provides a reliable guarantee of the correct tightening torque of the spark plugs.
- 3. Ratchet drive - It is used in a set with a candle head and a torque wrench.
- 4. Extension - Depending on the model and its accessories, access to the spark plugs may be limited to varying degrees, so the use of extensions of the appropriate shape and design will greatly facilitate the procedure.
- 5. Tool for measuring and correcting spark plug gaps - There are several types of this type of tool available - make sure the tool is equipped with a feeler gauge that matches the size of your car's spark plug gaps.
In most cases, a special spark plug head is required to replace spark plugs (with soft lining inside) complete with a ratchet drive, as well as a set of wrench drive extensions and a tool for checking and adjusting the interelectrode gaps (see illustration above). A special tool is also available for safely disconnecting the BB wire tips from the spark plug shanks, although its use is not strictly required. Using a torque wrench will allow you to achieve the correct tightening torque for the candles.
It is best to keep a set of replacement spark plugs with a correctly adjusted electrode gap in the car at all times. When buying new spark plugs, make sure that they meet the requirements of your car engine in terms of their parameters. The necessary information is given in Specifications to this Chapter, as well as on the VECI label attached under the hood (in case of discrepancy, preference should be given to the requirements of the latter).
1. Proceed to turning out the candles only after the engine has completely cooled down. In order not to waste time in vain, use the pause to check the status of the replacement kit. Carefully inspect the new candles, if the slightest cracks are found in the insulator, the corresponding candle should be rejected. Measure the electrode gaps of the new set (see below).
2a. The gap between the electrodes of the spark plug is checked by inserting the appropriate meter probe into it and must comply with the requirements given on the VECI label (see also Specifications to the head Engine electrical equipment). The required thickness of the probe should slide between the side and center electrodes of the spark plug with slight resistance (refer to accompanying illustration).
2b. The gap can be adjusted using a special tool, usually included in the meter. Bend the side electrode of the spark plug accordingly (refer to accompanying illustration).
3. If the side electrode is not positioned exactly above the center electrode, correct its position accordingly. Check for cracks or other damage in the porcelain insulator of the spark plug. The presence of any kind of defects in the insulator is unacceptable.
Removing
1. In order to avoid violation of the ignition order when connecting the coils, each of the candles should be serviced individually. Disconnect the coil from the spark plug of the first cylinder, in any case do not pull on the wire!
Note. On models with a 2UZ-FE engine with ignition coils located above the candles, in order to gain access to the candles, the entire assembly must be removed from the cylinder head cover (see chapter Engine electrical equipment).
2. If you have a source of compressed air at hand, use it to remove debris from the spark plug niches of the engine (For this purpose, a conventional bicycle pump is no worse).
Attention! Remember to wear protective goggles when using compressed air!
3. Remove the spark plug.
4. Check the removed spark plug against the identification card below to give a good idea of the overall condition of the engine.
Installation
1a. Before screwing in new spark plugs, lightly lubricate their threads with anti-seize sealant (refer to accompanying illustration). Thread one of the new spark plugs into the appropriate hole in the engine by hand. After making sure that the candle is not skewed in the thread, tighten it with the required force (with a torque wrench handy).
1b. To facilitate the procedure for baiting a candle, pull a piece of flexible fuel hose onto its shank (refer to accompanying illustration). This eliminates the possibility of thread breakage, since at the slightest biting, the hose will simply begin to turn.
2. Rotate the coil onto the spark plug shank.
3. Repeat the procedure for the remaining spark plugs.
Spark Plug Status Map
The normal state of the candle
Symptoms: Gray-brown color and slight wear of the electrodes. The number of glow plugs corresponds to the type of engine and its general condition.
Recommendations: When replacing spark plugs, use spark plugs of the same type.
Wear
Symptoms: Rounding of the electrodes with a slight accumulation of deposits at the working end. The color is normal. Causes engine start difficulty in cold, wet weather and increased fuel consumption.
Recommendations: Replace the spark plugs with new ones of the same type.
Coal deposits
Symptoms: The presence of soot indicates an over-rich air/fuel mixture or a weak spark. Causes misfiring, difficult starting and engine instability.
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 plugs with a longer insulator, which increases fouling resistance.
Ash formation
Symptoms: Soft brownish deposits on one or both spark plug electrodes. The source of their formation is the additives used in oil and/or fuel. Excessive buildup can insulate the electrodes and cause misfiring and engine instability when accelerating.
Recommendations: If deposits build up quickly, change the oil seals to prevent oil from entering the combustion chambers. Try changing the brand of fuel.
Oiling
Symptoms: Lubrication of the spark plug is caused by wear on the valve stem seals. Oil enters the combustion chamber through worn valve guides or piston rings. Causes misfiring, difficult starting and engine instability.
Recommendations: Carry out mechanical restoration work and replace the spark plugs.
Closing the electrodes
Symptoms: Waste products of combustion enter the interelectrode space. Solid deposits accumulate, forming a jumper between the electrodes. Leads to ignition failure in the cylinder.
Recommendations: Remove deposits from the interelectrode space.
Overheat
Symptoms: Porous, white insulator, electrode erosion and absence of any deposits. This will shorten the life of the spark plug.
Recommendations: Check if it meets the requirements Specifications number of glow plugs installed, ignition timing correct, air/fuel mixture too lean, intake manifold vacuum leaks, and stuck valves. Also check the coolant level and check if the radiator is clogged.
Too early ignition
Symptoms: The electrodes are melted. The insulator is white, but may be dirty due to misfiring or foreign particles entering the combustion chambers. May lead to engine failure.
Recommendations: Check the glow number of the installed candles, the ignition timing, the quality of the mixture (isn't it too poor), whether the cooling system is clogged and the lubrication system is functioning properly.
Electrically conductive gloss
Symptoms: The insulator has a yellowish color and a polished appearance. It speaks of a sudden increase in temperature in the combustion chambers during sharp acceleration. At the same time, ordinary deposits are melted, acquiring the appearance of a varnish coating. Causes misfiring at high speeds.
Recommendations: Change spark plugs (colder, while maintaining driving style).
Detonation
Symptoms: Insulators may be chipped or cracked. Insulator damage can also result from inaccurate spark plug gap adjustment. May damage pistons.
Mechanical damage
Symptoms: May be caused by foreign material entering the combustion chamber or by the piston hitting a spark plug that is too long. Lead to cylinder failure and piston damage.
Recommendations: Remove foreign particles from the engine and/or replace. Since the service life of the candles is usually 15,000 km, it is sufficient to clean them every 8,000 km.
Splashing
Symptoms: After misfiring for a long period of time, deposits can loosen while maintaining the operating temperature in the combustion chamber. At high speeds, deposits flake off the piston and adhere to the hot insulator, causing misfiring.
Recommendations: Replace spark plugs or clean and reinstall old ones.