We check the internal combustion engine with a gas analyzer - does it make sense?

The majority of motorists with experience have a clear stereotype in their minds: a gas analyzer is a device with which once "traffic cops" were forced to part with a certain amount from your wallet. In short, this thing is completely useless. However, this is not at all the case! This device, when used correctly, helps to detect many problems that an engine has.

What does a gas analyzer measure?

Everyone is familiar with the content of CO and CO in the first place.₂. The device measures oxides and carbon dioxide as a percentage. However, exhaust gases contain many other substances that are no less harmful. They are only measured in parts per million (parts per million or ppm for short), that is, 10 thousand ppm is just 1%. This means that very little of these substances is enough to harm the environment and human health.


So what does a running car engine “emit” and what can an analysis of the substances contained in the exhaust “tell” about?

Nitrogen oxides

Their amount should not exceed 1000 ppm (0,1%). NO NO₂ and other similar compounds are the strongest carcinogens, causing a whole host of diseases, the most "simple" of which is lung disease. In the worst case, it can come to cancer, problems with the heart, blood vessels. Therefore, there is nothing surprising in the fact that modern environmental requirements for cars are constantly tightening.


Previously, a simple recirculation system was installed in the machines, which allowed the use of exhaust gases. But even she irritated many car owners who considered her useless, and even harmful. Today, complicated EGRs with a pair of circuits are often installed on vehicles. Just this system reduces the amount of nitrogen oxides in the exhaust. And if there are a lot of them, what does this mean?

Causes of the problem

First of all, you should make sure that the EGR itself is working, in which a special valve plays one of the main roles. If it is jammed, the system will stop working, there will be no recirculation. As a result, all gases in "full composition" will fly into the silencer. While with a good EGR, they should partially return to the intake manifold (at idle and light load, the simplest systems do not function). A distinctive feature of nitrogen oxides is that their formation requires increased heating and a good load.



If your EGR is good, high NO levels may indicate an abnormal engine operating temperature. Here it is recommended to check the cooling system. At the second stage, it is worth making sure that the composition of the fuel mixture is normal. If it is lean, it will burn slowly and the motor will overheat. And the "bonus" can be the burnout of the valves operating at the outlet. Recall: the optimal composition is 14,7 parts of air and 1 fuel. Only in this case the mixture burns out completely and a minimum of harmful substances is thrown out.

Oxides of carbon

COXNUMX emitted by the exhaust system₂ is practically harmless to humans. This compound is formed by the reaction of CO and O₂. The first of these is carbon monoxide - the most dangerous for humans. Its “meanness” is that it has neither smell nor taste. Having inhaled CO, a person can lose consciousness, and in the worst case, die. Remember how suicides sometimes act: they close in the garage, the car and start the engine.


The high content of carbon monoxide is a consequence of the combustion of an over-enriched mixture. There are many reasons for this. For example, incorrect operation of the oxygen sensor (lambda probe) or throttle valve, leaking nozzle. Sometimes it is a banal air filter clogged with dirt or a non-functioning engine crankcase ventilation. Here it is already difficult to do without serious diagnostics using special equipment.

oxygen and nitrogen

In its pure form, these chemical elements will not bring any harm to health. Remember, the air we breathe is mostly composed of them. However, the presence of these substances in the exhaust in excessive quantities can also tell something. Nitrogen is not involved in the formation of the fuel mixture, so a lot of it or a little does not affect the "well-being" of the engine. Well, except that this element contributes to the formation of its harmful oxides (see above). Another thing - Oh₂. Its content in the exhaust is allowed up to half a percent. And if more?

Then the first thing to do is to look for where it sucks air. Oxygen, which the ECU did not take into account at the inlet, cannot burn out and makes the mixture lean. But Oh₂ the exhaust gas analyzer “calculates” well. The second point is to check the performance of the fuel system. It is likely that the amount of air entering is normal, and not enough fuel. There are also “sea” reasons: a poorly functioning gas pump, a clogged filter, failed nozzles, etc.


A gas analyzer will help you figure this out. If there is a lot of oxygen only at idle, most likely it is sucking air somewhere. The cause may be a broken cylinder head gasket, cracked pipes (for example, crankcase ventilation), which is typical for cars with high mileage. Even a torn corrugation coming from the air filter can be the "culprit". When an increased oxygen content is detected only at medium and / or high speeds under load, the cause should be sought in the fuel system, which does not “give out” a sufficient amount of fuel to the mixture.

Water vapor

Also completely harmless. But if there is a lot of it, this may indicate that coolant has entered the cylinders due to the same punched head gasket. In the worst situation - cracks in the BC, cylinder head.


Steam is immediately visible: thick white smoke from the exhaust pipe, which does not disappear after the engine warms up.

Hydrocarbons CH

There are very few of them, so hydrocarbons are measured in ppm, which we mentioned at the very beginning. For a serviceable internal combustion engine, the norm of these substances is up to 50 ppm. Although ideally, which is not achievable, they cannot exist at all. CH are formed by the constituent components of the fuel, which must be completely burned. If not, the most likely cause is a misfire. This malfunction is well shown by the on-board computer, if any.


But it is much worse when a high content of CH is the result of low compression. There are also many reasons: wear of the rings, their occurrence, deposits on valves that do not close completely, scuffing. In general, at a minimum, you will have to remove the head, at most - fork out for an overhaul of the engine.

Natural gas analyzer

This device is not so common today: even an average-priced scanner will “tell” more about the engine. However, each person has his own "device" - a nose! Carbon monoxide cannot be smelled with it. But if you have run the garage several times, even if the ICE is dizzy for a short time, there is cause for concern. If the exhaust smells like gasoline, the fuel does not burn out completely, there are a lot of CH hydrocarbons (see above). Watery eyes next to the muffler?


The point is nitric acid: it is possible that the engine overheats regularly, there is air leakage. Unfortunately, "smelling" pure oxygen or nitrogen will not work. But you should not abuse this method of troubleshooting: substance abuse is worse than a poorly functioning motor!