What Clearance Should Be In Ignition Trimmer

Even after purchasing and installing a new set of candles, various troubles sometimes arise. Motor operation may be uneven, jerking, as well as knocking, are observed. Not everyone knows what clearance should be on candles. It is worth correcting this gap, and the motor will work again, as expected.

What it is?

This gap is the distance between the two electrodes. It is necessary for the optimal ignition of the fuel mixture and the normal operation of the candle itself. If this distance will even slightly differ from the standards recommended by the manufacturer, then you can forget about the smooth operation of the engine. The car twitches during acceleration and uniform movement, detonation is also observed.

What Clearance Should Be In Ignition Trimmer

Ignition work in the combustion chamber

Candles are the latest element in the ignition of a car. They are constantly in direct contact with a mixture of gasoline and air. It is candles that ignite the combustible mixture. And ignition can be effective, as it should be according to technical regulations and ideas of engineers, or with low efficiency due to the influence of certain factors.

After the fuel-air mixture enters the engine cylinder, the piston will go up. Thus, the mixture is compressed. At the moment when the piston reaches its peak or dead center, the Hall sensor or ECU gives an impulse or command. As a result, the mixture ignites. The spark is responsible for ignition – an electric spark jumps between its two electrodes, which provokes the combustion of the fuel mixture.

But this burning may not be. This is not necessarily related to any malfunction in the ignition system. Just set the wrong gap. So, misfires may occur, due to which the engine efficiency is significantly reduced. Sometimes the motor may not start at all.

The effect of spark gaps on engine performance

Let’s look at how the gap between the spark plug electrodes will affect the operation of the engine. This is an important parameter that should be considered when diagnosing a power unit.

Small clearance

In the case when the gap is insufficient, gaps can be observed during ignition of the air-fuel mixture. A spark formed between two electrodes that are close to each other is too weak to ignite a combustible mixture. It may even be strong enough, but not enough to maintain stable combustion.

Therefore, cars can twitch when driving, slowly gain speed, not develop full power. In the carburetor power supply system, the spark plugs are often also filled with fuel – the engine will troit. You can solve the problem by increasing the clearance in the candles.

How to understand that he is small? Speaking of dimensions, the gap can be 0.1-0.4 millimeters. It is important immediately after purchase to check the distance between the electrodes and, if necessary, adjust it.

Large clearance of candles

Most candle manufacturers set normal clearances. However, during operation, the distance between the electrodes may increase. The gap does not grow by itself, but because of wear. It manifests itself if the candle works long enough. The electrodes are metal, and they have to work under the influence of discharges and high temperatures. Over time, these elements burn out. In this case, both electrodes are affected – the upper and lower. The first is made thinner, rounded off. And the second goes down.

For this reason, the power of the spark decreases, and quite significantly. A large gap in the candles also can not normally set the fuel mixture on fire. For this very reason, breakdowns often occur on the insulator of the lower electrode. The spark will surely find the shortest path for itself. In winter, the car may not start at all.

One more important point should be noted. On electrodes, the gap of which is too large, carbon deposits are more often formed. The spark suffers from a large gap, and here is also a black dense coating. Ignition on such a candle may not pass at all. It is important to periodically twist the candles and change or clean them. It is recommended to do this every 15 thousand kilometers. A large gap is the distance between the electrodes of 1.3 mm or more.

What is the norm?

What clearance should there be on candles if the lower limit is from 0.4 mm and the upper limit is from 1.3 mm? The optimal parameter for each motor will be different. First of all, different gaps are needed based on different ignition systems. For injection engines, a distance of 1 to 1.3 mm can be considered a normal clearance.

For carburetor engines, where the ignition is based on a distributor and a Hall sensor, the distance between the electrodes from 0.5 mm to 0.6 mm is considered normal. If the ignition is electronic (and this is not uncommon on modern cars), then the clearance on the VAZ-2170 spark plugs should be in the range from 0.7 to 0.8 mm.

Video: What Clearance Should Be In Ignition Trimmer

As you can see, the difference is quite substantial. It’s all about different ignition systems. Carburetor cars have low voltages, and the spark here will be weaker. Accordingly, the clearance should be minimal.

On injection engines, the ignition is more powerful. The electrical system is characterized by high voltages. That is why the normal clearance on the spark plugs for the injector is greater. If the distance is less, then the motor will not work stably.

Check and set the clearance

Measuring the gap is very simple. First you need to unscrew them, clean, and then take measurements. It is best to use a probe to measure the clearance. But if it is not, you can get by with the usual ruler.

The adjustment is also extremely simple – with a smaller gap with a screwdriver or something else, the electrodes are pushed apart. If the distance is greater, then you can tap on the upper electrode with something.


If the engine is unstable, if there are misfire, if it seems that the engine is troit, the first thing is to check what the clearance should be on the candle. The resource and serviceability of the internal combustion engine depend on this.

At the moment, there are several types of internal combustion engines – gasoline and diesel. And if the mixture’s arson is not required for the operation of the latter (it burns from the compression force), then in the case of gasoline a spark is needed. It is produced by a special element – a candle. Those are available on injection and carburetor machines. During operation, motorists often wonder what kind of clearance should be on the candles. Today we will talk about this topic in more detail.

About the ignition

A candle is the last element that comes in contact with the fuel-air mixture. Its main function is to set fire to the fuel at the moment when the piston is at top dead center. Voltage is supplied from high voltage wires. In turn, the interval between the supply of a spark is set by the ignition coil. When the piston is at TDC, a spark runs between the spark electrodes. She is the catalyst for this process.

The mixture ignites, the compression energy is transmitted to the piston. After the removal of gases, the process is repeated again. However, in order for the spark to be able to pierce the electrodes normally and ignite the mixture, the gap should be optimal. During operation, it changes. So, distinguish between small and large gaps. How they affect the operation of the engine, we will describe further.

What is the effect of small clearance?

If the gap between the electrodes is small (less than 0.4 millimeters), this will primarily be manifested in the nature of the engine. In this case, the owner will observe misfire. Why is this happening? The fact is that a powerful spark is required to set fire to a combustible mixture. And since the distance between the electrodes is small, then its strength will be insignificant. As a result, the combustible mixture will ignite once. The motor starts to troit. On carburetor aggregates often "floods" candles. This is not very good, as the motor operates in overload mode.

Large clearance is not always good

Therefore, if the spark is weak with a small gap, it must be maximized. But it is not so. If the gap is 1.3 millimeters or more, the spark will simply not pass between the electrodes. The motor will start to troit again. In addition to this, a candle deposit will appear.

How often to check?

Note that the manufacturers themselves do not oblige to check and adjust the gap (including iridium candles). However, practice shows that over time this parameter automatically changes in one direction or another, since the candle is constantly under voltage and high pressure. What to do in this case? Experienced motorists recommend checking the clearance on spark plugs every 15 thousand kilometers and, if necessary, correcting the readings.

What is the norm?

So, we have certain data. Small clearance is everything below 0.4 millimeters. Large – 1.3 and above. What clearance should be on candles? It all depends on the type of food. On carburetor cars with a distributor ignition system, this parameter is 0.5-0.6 millimeters. But not all units should have such a clearance on the candles. The carburetor with electronic ignition works fine with a clearance of 0.7-0.8 millimeters.

Spark plug clearance for gas

How to set?

If you notice that the car began to behave differently, misfires appeared, it is worth checking the condition of the candles. They may have the wrong clearance. To adjust the parameter, disconnect the high-voltage wires and unscrew the candle with a special key (as in the photo below).

So, we pass to setup. Using probes, we determine the exact clearance on the spark plugs. Please note that on cars with a contact system (old Zhiguli and Muscovites) this parameter is 0.1 mm lower than on contactless ones. If the gap is less than normal, the electrode is bent with a flat screwdriver. If the value is higher, the element is pressed with the same tool, only on the other side. Some candles may have a lateral arrangement of the electrode (and there are several).

In this case, a gap is set for each element. Take-off should be minimal. Having set the gap of one candle, we twist it into place, put the armored wires and proceed to set up the next one. It is important not to confuse the location of the high voltage wires. Therefore, twist the candles one at a time, and not all at once. Or make special marks. Otherwise, the motor may simply not start. At this stage, the setting of the spark plugs can be considered complete.

Why is sticking so important?

A correctly adjusted candle is not only the key to the coordinated operation of the engine. The clearance parameter also affects fuel consumption. By setting the desired distance between the electrodes, you will reduce it by 5-6 percent. Also, the normal clearance positively affects the life of the candle itself, since it will no longer pierce the insulator.

If you regularly monitor this parameter, the life of the candle can reach 60 thousand kilometers. This applies to both injection and carburetor engines.


So, we found out what the clearance should be on the candles, and how to properly adjust it. As you can see, the procedure is very simple. Even a novice motorist can cope with it. In conclusion, we note that the gaps need to be checked on new candles (the central electrode may have been bent during transportation). That’s all. We hope this article helped you solve this issue.