Before we talk about the device, operation and diagnostics of the lambda probe, let's turn to some features of the fuel system. We will be assisted in this by the magazine's expert, Fedor Alexandrovich Ryazanov, a diagnostician with extensive work experience, head of training courses for diagnosticians at the InzhKar company.
The modern motorist wants to own a powerful, but at the same time economical car. Ecologists have another requirement - the minimum content of harmful substances in the exhaust of the car. And in these matters, the interests of motorists and environmentalists eventually coincide. And that's why.
It is known that when the engine does not burn all the fuel, fuel consumption increases, and the cost of operating the car also increases. The power of the engine (or internal combustion engine) under conditions of incomplete combustion of the fuel inevitably drops, and the torque decreases. At the same time, the level of harmful substances in the exhaust of the car increases.
In this regard, one of the main tasks of modern automotive industry is the most complete combustion of the fuel mixture in the engine.
Combustion of the mixture is directly affected by its composition. The ideal situation is the stoichiometric composition of the fuel. In simpler terms, the proportion must be observed - 14.7 kg of air should account for 1 kg of fuel. It is this ratio that allows you to optimally use both. The owner of the car receives more torque and, as a result, adequate acceleration of the car, uniform engine operation in all operating modes. Fuel consumption also drops, and the car stops polluting the environment.
Deviations from the correct composition of the fuel mixture - rich and lean mixture. A rich fuel mixture is formed when there is little oxygen in the cylinders, but a lot of fuel, which, of course, due to a lack of oxygen, cannot completely burn out. Consequently, a car running on a rich mixture will consume more fuel, and an excess of unburned fuel, in this case, will cool the combustion chamber, engine power will decrease, unburned fuel will enter the atmosphere, polluting it.
Another situation: the engine receives a lean fuel mixture. In this case, the fuel in the cylinders will not burn completely due to a lack of fuel. In this case, you will also have to forget about the economy for which such engines were developed. After all, a lean mixture does not burn well, and this automatically leads to a drop in torque. The driver has to press on the gas more, which in turn leads to excessive fuel consumption.
Thus, it is clear that from all aspects, only the stoichiometry of the fuel mixture (proportion 14.7/1) is the most optimal mode of engine operation. And, of course, a car that has just rolled off the assembly line usually fits into all the limits of this criterion. But the "factory" setting may differ from the ideal. Moreover, during the operation of the car, wear of some components inevitably occurs, the sensors responsible for setting the fuel system may lose the accuracy of the settings. As a result, the composition of the fuel mixture is increasingly moving away from ideal indicators.
In this case, a lambda probe is just needed, it captures the amount of oxygen in the car's exhaust. And if there is a large amount of oxygen in the exhaust, this “signals” a lean fuel mixture and, conversely, if there is no oxygen in the exhaust, this indicates that the mixture has become rich. And we have already found out that in both cases, the engine power decreases, fuel consumption increases, and the environmental friendliness of the exhaust decreases. The task of the lambda probe is precisely to correct these deviations.
Let's take the following situation as an example: nozzles in the fuel system are clogged, their performance has decreased, the mixture has become lean. The lamb probe fixes this fact, and the fuel system control unit reacts to this information and “tops up” some fuel into the cylinders. This is how deviations that occur are corrected, taking into account the readings of this sensor.
Thus, the main purpose of the lambda probe is to compensate for deviations in the composition of the fuel mixture that inevitably occur during the operation of the car.
However, you need to understand that the lambda probe as such is not a panacea for all ills, it only allows you to return the composition of the fuel mixture to a state of stoichiometry. But this is not the elimination of defects, but only their compensation.
Let's get back to our injectors. When the injectors are dirty, the efficiency of atomizing gasoline is impaired, the fuel is atomized in large drops, they evaporate with difficulty. And the fuel supply system calculates the volume of fuel that is necessary to achieve the state of stoichiometry, for this, the readings of the air flow sensor are recorded. However, if gasoline in the system is sprayed in large drops, its vapors do not completely mix with air, some of the vapors burn out, and some of the gasoline droplets simply fly out into the exhaust pipe. The lambda probe interprets this situation as a lean mixture, and the fuel system sensor, which "does not see" individual drops of gasoline, adds fuel to bring the mixture to a state of stoichiometry. But in this case, fuel consumption rises sharply.
Therefore, for the operation of the lambda probe, it is not the factor of how the system copes with bringing the mixture to stoichiometry that is important, but the factor of what “price” it manages to do this.
Consider the oscillogram of the lambda probe. The sensor itself cannot distinguish between a stoichiometry state and a rich fuel mixture state, since there is no oxygen in the exhaust in either case. In the absence of oxygen in the fuel, the control unit (ECU - electronic control unit) slightly reduces the amount of fuel supplied to the cylinder. As a result, oxygen appears in the exhaust.
And in this case, the readings of the lambda probe are below 0.4 V, which for the sensor is a sign that the fuel mixture is lean (LEARN). At low lambda probe values (below 0.4 V), the control unit increases the fuel supply by several percent, the mixture becomes rich and the sensor readings reach a level above 0.6 V. The ECU interprets this as a sign that there is a rich mixture (RICH) in the fuel system. The fuel supply decreases, the readings of the labda probe fall, the cycle repeats - the composition of the mixture begins to fluctuate. In time with the change in the composition of the mixture, the readings of the lambda probe change. The ECU understands such fluctuations as a normal phenomenon, indicating that the composition of the fuel mixture is in the stoichiometry zone.
Recall also that the catalyst of the car must contain zirconium, this metal is able to accumulate oxygen. And in the lean mixture phase, oxygen is stored in the catalyst, and in the rich mixture phase, it is consumed. As a result, at the outlet of the fuel mixture, the catalyst burns out all its residues.
At idle, such oscillations occur with a frequency of one oscillation of about one second. The time of such a switch is another important indicator for a lamb probe. In our case (see oscillogram, Fig. 1), the switching time was 88 ms, while the norm is 120 ms.
If the switching takes a long time, as in the case of our oscillogram (see oscillogram, Fig. 2) - 350 ms, and besides, this situation is repeated many times, the control unit will generate an error: “slow reaction of the lambda probe”.
The values at which this error appears are determined mainly by the settings of the control unit software.
Thus, for diagnostics using a lambda probe, it is necessary to study the switching phases of the sensor. And if at least one switch from low to high reading appears on the oscillogram (maximum - 1V, minimum - 0V), this means that the lambda probe is working properly. A good sensor makes approximately one switch per second. Recall that in the operation algorithm of the control unit, lambda probe readings below 0.4V “beep” about a lean mixture, and above 0.6 V about a rich one. Therefore, it is possible to assess the state of the vehicle’s fuel system by the sensor operation. In our case (see oscillogram, Fig. 3), the control unit managed to compensate for all defects and derive stoichiometry.
Let's go back to the example with dirty injectors. With a lean mixture, the readings of the lambda probe fall below 0.4V. The control unit adds fuel until the mixture becomes rich. Note that in this case, the control unit “on its own” deviated from the parameters set by the manufacturer in its map. He records the deviation value in his memory as a fuel correction (fuel trime). The maximum allowable fuel correction for most modern cars is ± 20-25%. Correction in "plus" means that the unit had to add fuel, correction in "minus" - on the contrary, reduce.
Suppose the malfunction is of a long-term nature: the control unit has already reached the fuel correction limit, the error code lights up - “Fuel correction limits exceeded”. By erasing the code, such a defect cannot be corrected, and the presence of this malfunction will entail excessive fuel consumption. It is worth noting that problems are already detected at 15% of the fuel correction: the car almost does not drive, but consumes a large amount of fuel.
That is, it is important to remember that the fuel correction indicator and the operation of the lambda probe are a complex parameter, it indicates the presence of a defect, but does not indicate a specific cause that will have to be found and eliminated at a car service.
And a little about the structural features of the lambda probe. Such a sensor has a zirconium cone, which is placed on one side into the exhaust gases. Zirconium is a unique material because oxygen can pass through it. The oxygen ion, "sticking" to the zirconium atoms, moves along them, while a voltage appears on the zirconium cap. And if everything goes in the normal order, then the diffusion of oxygen ions is carried out evenly, and the voltage on the cone plates is 1V. If oxygen appears in the exhaust, diffusion is impossible, and the voltage in this case is 0V. Titanium oxide can be used instead of zirconium in lambda probes. The difference between a zirconium lambda probe and a titanium one is that the first one generates voltage, and the other changes its resistance (in the range from 0 to 5V), and it needs a circuit that converts the changing resistance into voltage.
A layer of platinum on a cone over zirconium allows you to remove stress from it, plays the role of a catalyst, burns gasoline and unburned oxygen. Everything worsens when using low-quality fuel, as well as fuel additives, which literally clog the layer of platinum and zirconium, and the probe fails. However, in this case, if the probe is not physically damaged, a normal flush will return it to working order. "Modern scourge" is the addition of anti-knock additives to fuel. Until recently, ferrocent was used as an additive - a dangerous substance that we dubbed "red death" for its red tint, as well as for the ability to quickly disable candles, lambda probes and a catalyst, ”notes Fedor Alexandrovich. The probe can "freeze" in the high or low position, i.e. either in the rich phase or in the lean phase. And in this case, the sensor will reach the limits of fuel correction and stop trying to equalize the composition of the mixture to stoichiometry.
We start diagnosing the state of the fuel supply system by connecting the scanner to the car. The absence of the code "Exceeding the limits of fuel correction" does not mean that there are no defects in the fuel supply system. It is necessary to make sure in the Data Stream that there are fluctuations in the lambda probe (stoichiometry has been achieved), and also, by the value of the fuel correction, to estimate at what price it was achieved.
Summing up, we note once again that when checking the lambda probe, it is necessary to pay attention to sensor fluctuations, if any, the sensor is working; if the lambda control system does not fluctuate, this may indicate either a malfunction of the lambda probe or a poor or rich fuel mixture. That is, you first need to check the sensors themselves. To do this, you need to forcibly enrich or lean the mixture in order to get fluctuations in the lambda and make sure that it is working.
The lambda probes discussed above are called "jump". Those. they indicate whether there is oxygen in the exhaust or not. But increasingly stringent environmental requirements have forced manufacturers to develop sensors that can not only work on the “Yes-No” principle, but also determine the percentage of oxygen in the exhaust. Such sensors are called "broadband oxygen sensors".
The principles of their operation and the features of car diagnostics based on the readings of broadband lambda probes will be discussed in the following publications.
OPINION
Maxim Pastukhov, DENSO Rus technical specialist: “Practice shows that the main reasons for the failure of lambda probes are: 1. Contamination of the lambda probe with fuel combustion products. In fact, these are additives that are used to increase the octane number of gasoline, eliminate detonation, or for other purposes. It also affects the degree of purification of the fuel. Additives, sulfur and paraffins “clog” the conductive layer of the lambda probe, and it “blinds”. The control unit puts the engine into emergency mode, and we see the "Check Engine" icon on the dashboard. By the way, spark plugs, valves, catalyst and other engine components also suffer from the above things. It makes sense to take a comprehensive approach to repair if the lambda probe is out of order. 2. Aggressive mixture, which is sprinkled on our roads. It corrodes the insulation of the wires and the wires themselves. To protect against this, we use double insulation of the wires, and also hide the place of welding of the wires with the sensor inside the lambda probe.”
There are many car malfunctions, due to which the further operation of the vehicle becomes problematic. Such malfunctions include an error in the operation of a car with the number P0171 or 0171. These numbers indicate the presence of a lean mixture. The causes of a lean mixture on the injector are quite diverse. First of all, you need to look at the condition of the machine while using a lean mixture.
Signs of a lean mixture
The error is displayed on the BC screen. This suggests that the amount of fuel in the air-fuel mixture is much less than air.
The presence is manifested in the form or delay when you sharply press the gas pedal. In other cases, the engine may triple or completely stop working at idle. In addition, during acceleration, the vehicle jerks, and the sound of the engine is completely different from the sound of the engine during normal operation. The operation of the power unit when using a lean mixture is not at all stable.
Norms of the mixture index and possible consequences
For cars with the Euro-2 standard and higher, a special sensor was installed on the engines - a lambda probe. He controls the quality of the mixture produced. According to the standard, it is established that 14 parts of air fall on one part of the fuel. If there is a minimum deviation of 0.25, the on-board computer will give an error about a lean mixture. When a lean mixture enters the engine, not only failures in operation appear, but also the possibility of engine overheating. RPM is quite low. In addition, if you do not carry out high-quality diagnostics and do not eliminate the cause of the formation of a lean mixture, then the consequences will become much more deplorable:
- overheating of the power unit;
- burnout of piston rings;
- burning valves;
- low engine thrust;
- piston burnout;
- increased consumption of fuel and lubricants and coolant.
Reasons and how to determine them
The causes of a poor air-fuel mixture (injector) are quite simple and lie in the operation of the car. You can determine them using engine diagnostics. First of all, the presence of such can be seen from the deposits on the candles.
Also, the causes of a lean mixture on the injector are associated with malfunctions in the fuel injection system. She is responsible not only for the supply of fuel to the power unit, but also for the correct preparation of the air-fuel mixture. In this case, it may be that the problem is related to the fuel or air supply setting. Because of this, the mixture is over-depleted. To solve the problem, the car owner should seek help from specialists, since a failure of the injection system can cover sensor malfunctions, improper adjustment of throttle angles. It also happens to be a rally of part of the firmware on the internal combustion engine. It is worth remembering that the composition of the mixture can change by some values only for a minimally short time. Otherwise, you need to look for the problem and fix it.
What to do in case of an error
The causes of a lean mixture on the injector (including the VAZ 2110) can be eliminated on their own if they are detected, however, the best solution would be to drive the vehicle to a specialized workshop, where auto mechanics will conduct high-quality diagnostics and be able to detect other malfunctions in the vehicle. It is also worth contacting a service station because most drivers simply do not know how to control and adjust the composition of the created air-fuel mixture. As a rule, on injection engines and on carburetors, the car owner has this opportunity. An example is the throttle valve opening angle adjustment. To do this, it is enough to change the position of the retaining ring, alternately moving it along the special grooves of the damper.
Self adjustment
Most drivers are very happy to be able to adjust the throttle angle, as they are completely confident that this will adjust the fuel consumption. In addition, some resort to the firmware of the electronic control unit of the vehicle. In order not to disable some units or ECUs, it is worth seeking help from qualified craftsmen who can, with the help of special programs, improve some car performance without affecting the quality of the mixture. Otherwise, the risk of "killing" the engine of your vehicle increases. Thus, a poor mixture is formed on the injector, the reasons (2114 is no exception) for which lie in the self-adjustment of angles or the intervention of an inexperienced car owner in the operation of the engine system.
Fuel system malfunction
Other causes of a lean mixture on the injector are the vehicle not working properly. As a rule, malfunctions occur due to low-quality fuel, which is poured at little-known gas stations. One of the options for unstable engine operation and the formation of a lean mixture is clogged fuel cells in a car. In such cases, there is a gap in the operation of the engine. As a result, the car may jerk. To prevent this from happening, it is necessary to purchase fuel only from trusted gas stations. Both fuel elements should also be replaced in a timely manner. Remember that one filter is presented on the injector in the form of a mesh and is installed directly in the fuel pump. The second element is most often located not far from the tank on the bottom of the car, less often - in the engine compartment. To avoid over-depletion of the mixture, it is necessary to change them at least once every 40,000 km. Sometimes this figure may be lower, since it all depends on the quality of gasoline.
Clogged nozzles
If you do not change the fuel elements of the car system in time, a lean mixture may form on the injector, the causes of which will lie in the incorrect operation of the injectors. That is, fuel is supplied, but is supplied in a fairly low amount. The nozzle is a special device related to the vehicle injection system. There are many elements: electromagnetic, electro-hydraulic or piezo-hydraulic. Gasoline vehicles use electromagnetic parts.
The reason for the failure is as follows. Fuel filters that are not replaced in time begin to pass fuel along with foreign substances over time, without conducting high-quality cleaning. Since the holes at the needle and nozzle of the injectors are rather small, the incoming fuel with foreign contaminants form deposits on the walls, due to which the already small diameter of the fuel passage decreases even more. As a result, the required amount of fuel does not enter the engine and lean mixture problems occur.
To solve the problem, you can restore the previous injection, which is carried out only using special equipment.
By the way, in order to avoid contamination of the injectors, the fuel tank should be cleaned at short intervals, as there is a large accumulation of dirt, sand or other substances.
Other causes and solutions
The system produces a lean fuel mixture at the injector. The reasons may be different. For example, it may be formed due to the presence of foreign objects, so you should inspect the pipes and hoses that go from the air filter for a tight seal.
Another cause could be a cracked intake manifold. Eventually, you will have to replace it. The cost of this part is quite high. In addition, air is sucked in from the place of the XX sensor. It is worth checking the sealing ring at the installation site.
Uncertain reasons
In other situations, it happens that a poor mixture is formed on the injector in a VAZ 2107 car, the reasons for this are completely unknown. The diagnostics carried out indicate the presence of a malfunction with a lean mixture, but does not allow determining the cause that led to its formation. In this case, you will have to search at random - to look through all the systems.
Firstly, the causes of a lean mixture on the injector can be caused by deposits of dirt on the connecting plugs, which interferes with the quality of the engine. You should also inspect suitable nozzles for air leakage. It is also necessary to flush the injector itself, since due to low-quality gasoline, strong carbon deposits form on the walls inside.
In this article, all the main reasons that affect the formation of a lean mixture were considered, thanks to which the driver will broaden his horizons and will be able to otherwise make repairs on his own. If you are a novice car enthusiast, you should not make repairs without experience, it is better to send the car for diagnostics to the service station. And most importantly - remember that timely elimination of the problem will increase the life of your unit.
Might be useful to someone. Auto Toyota Carina II (European), 4A-FE LB, 1.6L, manual. Ordered a long life sensor lean mixture (sensor, lean mixture), code 21, 89463-29035 (internal factory marking 89463-20050 NG 192500-0200). For the same one they asked for ~17K rubles. + wait up to 2 months until they bring it. After a long search and reading information on the internet, the sensor 89463-29045 was chosen, which was delivered in 1.5 weeks + 8K p. The connector, of course, did not fit, I had to cut it off from the old one. I didn’t solder the wires, but twisted and insulated them with a heat-shrink tube (I think that’s what it’s called). Mechanically everything came up, nothing had to be adjusted anywhere. I put a new gasket (it was included), installed the sensor, made a "reset" from EFI. Code 21 did not appear. Subjectively, the engine began to work somehow differently, softer, especially when the revolutions were over 2-3 thousand. It has not yet been possible to measure the flow rate, because everything is in the stage of behavior testing, but it is clear that the city is less than 10 liters.
background. Over the past winter, the warm-up revolutions have grown to about 3 thousand, the consumption in the city is somewhere around 12-15 liters. Spring drove the car to the local "Kulibin". He was tinkering with it for about half a day, after which the heating steels were around 1600 rpm, the heating itself takes from 5 to 15 minutes (if you stand), depending on the minus outside. After warming up, the speed drops to the prescribed 700-800 rpm. and a little "float" (visually on the tachometer plus or minus 30 rpm), while driving the car does not blunt and, in general, behaves normally. Kulibin himself did not admit what he was doing (apparently this is his know-how), hinted that he had cleaned some thing that is located in the coolant line in the throttle area, warned that my lambda was inoperative. I rushed to look for what is on my engine on existential and how much. As a result, it turned out that my engine is a European version of Lean Burn with one lean mixture sensor and no oxygen sensor.
By the way, before going to the mechanic, I cleaned the return valve and the BDZ using a carb cleaner. There was dirt! After a trip to the mechanic and the completion of the procedure for buying a new sensor, the oil was changed with a filter and coolant. Before installing a new sensor, the following was noticed: the morning plant is normal, the trip to work is also, if there were day trips - there was a drop in revolutions to 400-500 after cranking (then the revolutions went to warm-up for 1 minute) and at traffic lights, especially if there is a big "plus" on the street. The next day - the same situation. Apparently, it is necessary to check the adjustment of the BDZ and candles.
In general, for the entire period of operation (since 1998) of this car, I didn’t really get under the hood, I changed consumables at the right time and changed the cylinder head gasket a couple of times: the first time was the legacy of the previous owner (he had something leaking, which - something changed or not - it’s not clear) to the Chinese “thick” (swamp green), they warned that it didn’t pass for a long time, so it is, for about 7000 km. there was a "breakdown" of the gasket between the 2nd and 3rd cylinders about 1 cm wide, the result is the second replacement with the original (black, "thin"), it has been running for the 3rd year, it seems without problems. Both times - with polishing of the head.
Now I'm struggling with "dimming" in the head light, like the reflectors are dirty.
Here is such an experience. Good luck to everyone and a speedy and high-quality victory over the ailments of steel horses.
