When to change spark plugs: by mileage, by condition, or by performance

Why is it optimal to change spark plugs ahead of time?
The mileage through which it is recommended to change the spark plugs is regulated by the manufacturer. Trying to replace the original with something similar can result in serious engine damage. After all, it is not in vain that when we come to a car shop and ask to sell candles for our car, we are asked the make of the car and the year of manufacture. The glow index of the spark plug must correspond to the type of internal combustion engine.

If we talk about the resource, then the actual service life depends on the operating conditions and fuel.

Erosion entails a gradual increase in the spark gap to a critical value. If candles with a burned-out electrode are not changed for a long time, an unbearably high voltage will be required. This causes the following to fail:

ignition coils;
drive insulation;
candle tips.
In addition, driving with bad spark plugs increases gas mileage. Destruction of the electrode or insulator may result in motor replacement. Therefore, for preventive purposes, they rolled out the required resource – change even seemingly good samples.

The mileage resource according to the instructions can vary from 15 to 60, and even up to 100 thousand, if the factory has provided two or three side electrodes. Or if the material of manufacture is refractory platinum or iridium.

Signs of bad spark plugs
Evaluating the quality of work is quite simple. They brought their palm to the exhaust pipe – if there are no pops, flashes and the exhaust is smooth, then everything is fine. But this is on the outside.

Symptoms of a malfunction:

power loss;
power failures with increasing gas;
uneven exhaust, pops, uneven operation of the internal combustion engine;
engine troit;
vibration at idle.
Even for IX iridium spark plugs, the manufacturer recommends 30,000 miles. The main reason for such frequent replacement is gasoline with a large number of additives that increase the octane number.

As a result of poor fuel, wear of the electrodes and an increase in distance.

A sign of the use of bad gasoline on candles can be traced immediately – a red coating on the metal. The gap can be measured with a special probe. We looked at the instructions for what the gap should be – checked. If it is very large – change without a doubt.

How to clean and test spark plugs yourself
Your spark plugs are around 12k miles. They work fine but look bad and need to be cleaned. Before the operation, we will measure the resistance with a multimeter. After processing, we measure the second time. This is to ensure that the measurement result has not deteriorated.

We need to measure the electrical resistance:

check the breakdown on the body.
set the resistance on the multimeter to 20 kΩ.
We measure with probes:

case – central electrode;
body – the second electrode.
Isolation should be infinity.

Next dimension:

internal resistance between two electrodes.
The resistance should be about 5 kOhm. It won’t have the same value.

After measurement, dry cleaning can be carried out.

You can clean: citric acid, vinegar with baking soda, pharmacy dimexide, rust converter and even Coca-Cola.

Let’s use the most common ingredients that are in any home.

Take vinegar and fill the candles completely. After 30 minutes, pour a teaspoon of baking soda into the vinegar.

After another 10 minutes, we clean under running water, you can use an old toothbrush.

The surface became clean, even in a hard-to-reach place between the electrode and the thread. After drying with a hair dryer, the electrical resistance must be measured again. In the same sequence as before cleaning.

The resistance should not change. After measuring with a multimeter, you need to check the operation of the candles on the car. But first, let’s set the desired gap distance.

How to set the gap between the electrodes
To measure the gap between the center and side electrodes, use a spark plug probe. It is needed for fine tuning.

The distance depends on the ignition system. For example, for an injector, it can be from 1 to 1.3 mm. For a distributor-based carburetor: from 0.5 to 0.6 mm. At the same time, a lower value is suitable for a colder season, a higher value for warm weather. We select the probe of the desired diameter. If the probe does not pass or passes too freely, we bend or adjust the electrode to the size of the probe inserted into the gap.

Check spark plugs for spark
The battery must be charged.

We clean the place on the cylinder block where we will touch the metal with the side electrode.
We get a candle from the well.
We insert it into the ignition coil and start the engine.
The electrode must touch the cleaned metal.
There is a spark – all is well. There is no spark – the candle needs to be changed
The fastest way to find the faulty one is to remove the wires from all the spark plugs one by one and listen to the sound of the engine.

Checking high voltage wires and coils
If the test did not show anything, we check the high voltage wires.

Get the right candle. We start the engine. No spark – needs to be replaced.

Another sign that the high-voltage wire is faulty is a glow in the dark, penetration occurs at the site of poor insulation.

If one wire fails, the whole set needs to be replaced.

Engine condition by spark plug color
A candle can be called an indicator of the health of the internal combustion engine. By its condition, you can find weaknesses in the engine.

Terry black soot of the main electrode – increased fuel consumption, the gasoline engine injector does not work well, the carburetor is not tuned, the dirty air filter does not provide air flow.
Very light, gray or white center electrode – regular overheating of the candle or lean mixture. We need diagnostics of the fuel supply, cooling system and internal combustion engine electronics.
The red brick or red color of the skirt of the main electrode is bad gasoline, too enriched with additives. Change the gas station, otherwise both the candle and the lambda probe (oxygen sensor) will suffer.
Oiling of the threads and black carbon deposits – the sealing cuffs of the valves are faulty.
Oily skirt, engine troit – the timing valve is damaged, it is necessary to change the piston rings.
Destroyed, damaged insulator – detonation of the internal combustion engine, unusable fuel, incorrect spark plug set, early ignition timing.

Tips & Tricks
Do not rush to change the candles on a hot engine, you can get the threads from the cylinder head.
Do not neglect to clean the dirt around the cylinder block, even under the protective decorative cover there can be dirt and sand that can get into the wells and then into the cylinders. Hence, rapid wear and scuffing when foreign objects enter.
They turned up the candles, do not rush to get them right away – blow out the wells and only then take them out.
Candles are best taken according to the cylinder. This will help to understand if there is a defect in a particular cylinder, on a wire or coil.
Don’t rush to throw it away. Check the condition of the electrode, the presence of carbon deposits, the condition of the insulator for dashes, scratches – this indicates that the coil or wire may fail.
Check new spark plugs. Look for the presence of a distance sleeve with which you can adjust the gap. Check the gaps with a feeler gauge, compare them with the gap on the old candle.
Never throw a candle into a well. The electrode may be deformed. Use the candle key.
Tightening must be done completely. Underloading is fraught with decompression.

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