How to treat error 0171 lean mixture VAZ-2112 16 valves: causes

Sometimes a car owner encounters problems, the cause of which is very difficult to determine. Error P0171 is one of these problems. There are many versions as to why this error is displayed on the car panel. In this article we will look at the most well-known causes of error P0171 and tell the reader about ways to eliminate it.

What does error P0171 (“fuel supply system too lean”) look like?

At some point, a car owner may discover that a message with code P0171 appears on the dashboard of his car. This message can appear on any car if the engine management system in it is made according to the Euro-2 standard. In such systems, so-called lambda probes are installed, whose task is to monitor the chemical composition of the fuel mixture. The probe monitors that there are 14 parts of air to 1 part gasoline. The amount of air can deviate from this number in any direction, but no more than 30%. As soon as this threshold is exceeded, the driver sees error P0171 on the dashboard.

Reasons for appearance

As stated above, error P0171 occurs due to a lean mixture. This is the root cause. The problem is that the fuel mixture in a modern Euro-2 car can become lean due to a variety of different problems. It is not possible to list them all, so we will limit ourselves to the most famous:

All these problems lead to the fact that the mixture becomes lean and the engine cannot operate stably even at idle. And since a lean mixture burns more slowly, the engine quickly overheats, and the car does not pick up speed well.

Elimination method

It usually consists of three large stages:

Sensors

A clogged MAF (mass air flow sensor, mass air flow sensor) is the most common cause of error P0171. Dust and dirt accumulate on its wires over time. As a result, it does not immediately respond to changed air flow. It's not just dirt that can get into this sensor. Combustion products may be deposited on it, which come out of the throttle valve and from the intake manifold with vapors after the engine stops. Because of these vapors, a thin layer of paraffin appears on the wires, after which the sensor begins to send a signal to the system that there is little air in the fuel mixture. Something similar can happen with other sensors. All of them are thoroughly cleaned using a special spray for cleaning electrical appliances. The second solution to the problem is to completely replace all “suspicious” sensors with new ones. We should not forget about the service life of the sensors. They can simply serve their purpose. Example: it is recommended to change the differential pressure sensor every 80,000 km.

Tightness

If the previous point did not help in solving the problem, you need to check the fuel system for leaks. First of all, the throttle valve is checked for depressurization. Next, all places where the vacuum hoses connect to the exhaust manifold are checked. The hoses are also inspected for mechanical damage, and this applies not only to the intake manifold. It is necessary to inspect the hoses of the fuel vapor trap and crankcase ventilation. The rule is simple: at least within a radius of half a meter from the oxygen sensor, the system must be absolutely sealed. If this condition is not met, the sensor is guaranteed to produce incorrect readings, leading to an error.

Fuel system

If it has reached this stage, the first thing to check is the injectors. They are removed and installed on a special stand, which will give you an idea of their performance. Then the fuel pressure level in the system is measured. If it is too low, the fuel pump is removed and disassembled. It is inspected for contamination, leaking gaskets and mechanical damage. The voltage supplied to this pump is also measured. If none of this helps, check the fuel pressure regulator. If it is ok, you should check to see if the fuel filter is clogged. Many of the above problems can be solved with the help of a high-quality car scanner, the purchase of which should be taken care of.

Error P0171 is a problem that cannot be resolved without an integrated approach. Often, in order to remove an annoying inscription from the panel, a car owner has to literally shovel half of the car. But alas, no one has yet come up with a better way to solve this problem.

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Where does the “too lean mixture” error come from on the VAZ 2112: causes and solutions

Many motorists remember how a problem arose on carburetor engines when a lean mixture appeared due to the carburetor or filters, which not only slowed down the engine, but also increased consumption (consumption rates). With the development of the automotive industry, the reasons for the effect have become more numerous, since many new details have been added that regulate this indicator. No, all motorists know why a lean mixture can appear on a VAZ-2112, and even more so, how to solve this problem.

How to regulate fuel consumption on a VAZ 2112

We have already considered the factors and reasons that affect the use of gasoline in the VAZ 2112. Now you need to know what needs to be done to prevent gasoline consumption from increasing or how to reduce it. The main points to prevent increased fuel consumption are:

constantly change the fuel filter;
monitor the operation of the engine system;
change candles that become black and oily over the years - non-functional;
watch the condition of the fuel pump mesh so that it does not fall into the glass;
The catalyst and exhaust must function.

By adhering to these rules, you can save on fuel costs for the VAZ 2112 by 7.5 liters.

Basic rules for reducing gasoline consumption

An attentive driver must constantly monitor all indicators of the car. Monitor the oil level, monitor engine operation, and monitor all filters and strainers. If you bought a car that has already traveled a certain number of kilometers and its fuel consumption exceeds 10 liters, then you should immediately take the following actions:

change oil (adjust level);
replace the filter;
check the quality of gasoline;
observe the performance of the fuel pump;
regulate driving maneuverability.

If all this does not lead to the desired result, then you need to do computer diagnostics of the car.

Causes of a lean mixture

The error shows that the mixture is lean

How to determine the problem of the occurrence of a lean mixture effect in the engine cylinders? There are several reasons why this process may occur. So, let's look at all the possible options:

Now that all the reasons have been considered, you can move directly to elimination methods.

Making a poor mixture into a good one!

To eliminate the causes of a lean mixture, you will have to work hard, since there are quite a lot of components in which a malfunction could occur. It is worth considering the sequence of actions to find the problem area and eliminate the cause.

Problems in the ECU

The first place you need to look is the electronic control unit of the engine and its systems. Thus, the accumulation of errors in the ECU can lead not only to changes in the mixture, but also to other malfunctions. In order to eliminate the cause, you need to connect to the unit using a USB-Auto cable and look for any faults. Often, this is where the initial answer to the question lies. This or that error will show which node caused the malfunction. As practice shows, this may be one of the sensors.

Diagnostics of the ECU for errors

If, however, a large number of errors are detected during connection, then a reset is necessary. If it does not help, and the sensors are all working, then motorists recommend reinstalling the car software. It depends on the type of control unit that is installed on the vehicle.

Self-diagnosis and reset of ECU errors on the instrument panel

Sensors and electronics

Failure of one of the sensors can result in a lean mixture. So, exactly what indicators need to be checked for performance in engines:

Mass air flow sensor

The IAC sensor is located on the throttle valve

Throttle position sensor

After checking all these products, you need to connect to the computer and reset the errors.

It is also recommended to check the wires that go to the sensors for breakdowns. If necessary, damaged elements must be replaced and the error reset procedure repeated.

Fuel system

One of the main systems that leads to a lean mixture is the fuel system. The main reason is insufficient pressure in the fuel rail. This may be due to several reasons:

Mesh filter installed in the fuel module

Checking the fuel pump by immersion in water

Sectional view of the fuel filter after removal from the vehicle

Cleaning injectors without removing them from the car

Throttle

If the problem does not go away when repairing the fuel system, then you need to pay attention to the air supply system to the engine. So, the cause of a lean mixture may be a clogged throttle valve or air filter.

Dirty air filter removed from the car

To diagnose, you need to remove the filter element from its seat and inspect it. The presence of oil stains may indicate poor performance of the valve stem seals. A large accumulation of dust causes it to not allow air to pass through in the required amount. To fix the problem, you need to replace the element. The throttle also needs to be dismantled and inspected. If there is too much blockage, clean it with WD-40.

Cleaning the throttle valve

Ignition system

The last system where a lean mixture could be caused is the ignition system. So, it is necessary to diagnose the following elements:

Characteristics of different spark plugs

Error P0171 - Air/fuel mixture too lean, bank 1

Trouble code P0171 indicates that the vehicle's engine is running too lean (bank 1).

What does P0171 mean?

Trouble P0171 is a general trouble code that indicates that the engine's fuel system is not operating properly or there is a vacuum leak on the specified side of the engine (bank 1). If your car engine is running lean, it means that there is too little fuel or too much air entering the engine.

Causes of error P0171

The most common causes of P0171 are:

Fuel pressure regulator malfunction
Damage to the fuel pump
Fuel filter clogged
PCM (Powertrain control module) malfunction
Vacuum leak
Malfunction of one or more fuel injectors
Malfunction of one or more oxygen sensors
Malfunction of the mass air flow sensor

What are the symptoms of P0171?

The main symptoms of error P0171 are:

Engine power drop
Check Engine Light Illuminates
Engine stalling or erratic operation
Problems starting the engine
Complete engine failure
Damage to the catalytic converter (if the problem is not resolved for a long time)

How does a mechanic diagnose a P0171 code?

First, the mechanic will check the engine for vacuum leaks using a vacuum gauge. If there is a leak, a hissing sound will be heard. It can usually be heard clearly when the engine is turned off.
He will then check the fuel pressure sensor and mass air flow sensor using the fuel pressure gauge.
To maintain the correct air-fuel mixture ratio, the vacuum pressure and fuel pressure in the engine must correspond to the values specified in the manufacturer's specifications.
If no fault is found after performing the above checks, the problem is most likely a fault with one or more of the oxygen sensors.
The mechanic will check the operation of the oxygen sensors following the procedure set forth by the vehicle manufacturer.
If no problem is found, the mechanic will check the PCM (Powertrain control module).

Common mistakes when diagnosing code P0171

The most common mistake made when diagnosing a P0171 code is that mechanics do not consult the vehicle manufacturer's technical service bulletin for common troubleshooting tips before diagnosing the error.

Although recommendations may not be provided for all error codes, it is important to review the Technical Service Bulletin as in some cases this will save time and make it easier to diagnose and resolve the error.

How serious is P0171?

Error P0171 is considered quite serious, since when it appears, problems with the engine may occur.

If the air-fuel mixture ratio is incorrect, fuel consumption can significantly increase and engine power can decrease.

If this code is detected, it is recommended that you contact a qualified technician as soon as possible to diagnose and correct the error to ensure smooth operation of the vehicle.

What repairs can fix the P0171 code?

Replacing the fuel pump
Replacing the fuel filter
Replacing the fuel pressure regulator
Replacing the PCM (Powertrain control module)
Replacing one or more fuel injectors
Replacing one or more oxygen sensors
Replacing the mass air flow sensor
Repairing existing leaks

Additional comments for troubleshooting P0171

To avoid further damage to the vehicle, as well as costly repairs, if this code is detected, you should contact a qualified technician as soon as possible to diagnose and correct the error.

Need help with error code P0171?

The company - CarChek, offers a service - on-site computer diagnostics; specialists from our company will come to your home or office to diagnose and identify problems with your car. Find out the cost and sign up for on-site computer diagnostics or contact a consultant by phone

conclusions

It is quite easy to establish the cause of a lean mixture on a VAZ-2112, and knowing it, you can eliminate it. Of course, not all motorists are able to make repairs themselves. Therefore, if you are not sure that you can handle it, we recommend that you contact a car service, where they will do everything efficiently and quickly. Not always true!

We had such a problem on our 12. They suspected that fuel consumption had increased significantly. Unfortunately, we couldn’t handle it on our own and had to go to a service station.

For no apparent reason, the consumption increased greatly, I came to the guys for service, they established the reason, the air flow sensor was covered, well, they changed the filter to catch up.

Maybe someone knows (or has encountered) a problem like mine (VAZ-21103, 2001 year old, mileage 91,000 + km, one owner, no major problems have arisen over the entire period. Due to circumstances, the last three -four years, rarely used, annual mileage does not exceed 3,000 km, only gasoline). From time to time, the following situation began to appear: The car drives as usual, and then it stops moving, but does not stall, but simply does not pull. In this case (but not always), error 0171 appears (the system is too lean). Then, after several kilometers of torment, the car starts driving again, as if nothing had happened. I also noticed that when you press the gas to the floor, you get the feeling that the car doesn’t understand what they want from it. You start to take off the gas, she (!) suddenly begins to accelerate confidently! I have already adapted to the fact that in order to accelerate it, I look for the point of travel of the gas pedal at the very beginning, at which it begins to accelerate. If you press the gas a little, that's it, it starts to go dull! Sometimes it helps to remove the terminal for 10-15 minutes, after which everything returns to normal again. I went to diagnosticians (different ones), connected the scanner - no errors were visible, everything worked fine, the idle values were also normal. I arrived with error 0171, they say that the system is too poor and they say that there could be a lot of things. It’s possible to drive as you are, but it’s not entirely normal—there’s no certainty that while overtaking, the car might suddenly, for no apparent reason, become dull. Yes, such jambs, it gives out both in a straight line and on the rise...

How to resolve the error

Regardless of the cause of error P0172, you should not delay repairs; a rich mixture will shorten the life of the catalyst. The most likely sources of problems are checked and eliminated first:

Examine the candles. Check by the presence of black soot that the mixture is over-rich.
On vehicles with a return line, remove the hose from the regulator and try to bleed it to ensure it is not pinched anywhere along the way to the gas tank.
Find out the correct fuel pressure values for your car. For a VAZ with a drain ramp it is 3 bar, with a drainless one - 4. Please note that the pressure on the drain ramp is measured with the vacuum pipe removed from the regulator, otherwise the readings at idle will be 0.6-0.5 bar lower! The pressure gauge itself for measurement can be inexpensively purchased or borrowed.
Connect the tester to the signal wire of the lambda probe in voltage measurement mode. It is more convenient to use pointer instruments - they do not have the same inertia as digital ones; on a working lambda probe, you can see the needle oscillate from 0.25 to 0.75 V.
Measure the voltage at the output of the mass air flow sensor with the engine turned off, comparing it with the standard one, if it is possible to find it out. For example, for VAZ sensors it should not be higher than 1.03 V (Bosch) and 0.04 V (Siemens).
Check the level and condition of the engine oil.
Without “catching” the source of the problem, contact the service - for a qualified diagnostician there will be no problems here.

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Causes of a lean mixture

The error shows that the mixture is lean

Now that all the reasons have been considered, you can move directly to elimination methods.

Making a poor mixture into a good one!

Problems in the ECU

Diagnostics of the ECU for errors

Self-diagnosis and reset of ECU errors on the instrument panel

Sensors and electronics

Failure of one of the sensors can result in a lean mixture. So, exactly what indicators need to be checked for performance in engines:

Mass air flow sensor

The IAC sensor is located on the throttle valve

Throttle position sensor

After checking all these products, you need to connect to the computer and reset the errors.

It is also recommended to check the wires that go to the sensors for breakdowns. If necessary, damaged elements must be replaced and the error reset procedure repeated.

Fuel system

One of the main systems that leads to a lean mixture is the fuel system. The main reason is insufficient pressure in the fuel rail. This may be due to several reasons:

Mesh filter installed in the fuel module

Checking the fuel pump by immersion in water

Sectional view of the fuel filter after removal from the vehicle

Cleaning injectors without removing them from the car

Throttle

Dirty air filter removed from the car

Cleaning the throttle valve

Ignition system

The last system where a lean mixture could be caused is the ignition system. So, it is necessary to diagnose the following elements:

Characteristics of different spark plugs

How serious is P0171?

Measure fuel pressure - pressure gauges are inexpensive, you can find a suitable one from friends. The measurement is carried out both with the engine turned off and with it running. If even with the engine off, the pressure is below normal (for your car, find the exact value on the Internet - usually from 3 to 4.5 bar), then the fuel pressure regulator is most likely to blame: a “tired” fuel pump is usually enough to produce the required pressure in the absence of fuel consumption. But its drop while the engine is running is more like a pump malfunction or a clogged filter.
Was there any floating idle speed before? They will leak air into the intake even before the mixture begins to become too lean.
Check the air temperature sensor using the method described above.
It is difficult to assess the condition of the injectors “on the knee” - here it is better to contact a service center. By the way, it will be cheaper to bring them already removed and pay only for the work of the stand.

Seal

The main symptoms of error P0171 are:

Engine power drop
Check Engine Light Illuminates
Engine stalling or erratic operation
Problems starting the engine
Complete engine failure
Damage to the catalytic converter (if the problem is not resolved for a long time)

First, the mechanic will check the engine for vacuum leaks using a vacuum gauge. If there is a leak, a hissing sound will be heard. It can usually be heard clearly when the engine is turned off.
He will then check the fuel pressure sensor and mass air flow sensor using the fuel pressure gauge.
To maintain the correct air-fuel mixture ratio, the vacuum pressure and fuel pressure in the engine must correspond to the values specified in the manufacturer's specifications.
If no fault is found after performing the above checks, the problem is most likely a fault with one or more of the oxygen sensors.
The mechanic will check the operation of the oxygen sensors following the procedure set forth by the vehicle manufacturer.
If no problem is found, the mechanic will check the PCM (Powertrain control module).

Replacing the fuel pump
Replacing the fuel filter
Replacing the fuel pressure regulator
Replacing the PCM (Powertrain control module)
Replacing one or more fuel injectors
Replacing one or more oxygen sensors
Replacing the mass air flow sensor
Repairing existing leaks

Dirt in the air flow sensor, as a result of which it cannot correctly take into account air flow;
Vacuum leak;
The EGR valve, which is responsible for exhaust gas recirculation, does not close tightly enough and allows air into the intake manifold;
High air flow through the EGR valve due to a faulty EGR differential pressure sensor.

Insufficiently powerful fuel pump;
Fuel filter with resistance;
Dirty fuel injectors;
Leak in the fuel pressure regulator. To find the cause of the P0171 error, you need to outline the reasons why a lean mixture enters the engine and the check engine shows such an error. After this, a sequential plan for checking the car is drawn up:

Injectors and fuel supply system;
Tightness of intake and exhaust manifolds and accompanying hoses;
Air and oxygen flow sensors (mass air flow sensor and lambda probe).

Don't put it off until later, fix it as quickly as possible

But, in any case, you need to remember that long-term operation of a car with such a problem can lead to premature failure of many components and assemblies. As a result, the bill for repairing your car will be much higher than in the case of a simple check, which we described in the previous sections of this article.

Eliminating the error: mixture too rich

Therefore, in order to find the culprit component or system, you will need to check the MAF, DTOZh and lambda probe sensors with a multimeter. Then check the voltage and wires. Measure with a pressure gauge. Check the ignition marks. And also check the connections at the air intake and exhaust manifold for presence.

Once the problem has been resolved, you will need to reset the fuel trim to reset the long-term trim to 0%.

By following all the recommendations, you will probably be able to cope with incorrect engine operation and the setting of error code P0172 both in VAZ and foreign cars like Toyota or Mercedes, as well as other cars with electronic controls. Although it is often not necessary to complete all the points, in most cases it is necessary to flush or replace the mass air flow sensor or oxygen sensor.

Most modern cars still run on internal combustion engines - principles that are more than 150 years old. Despite all the electronic, intelligent filling, engines of all manufacturers are still susceptible to typical diseases and problems of internal combustion engines. One of these problems is a rich fuel mixture, which can make even a modern car with an injection engine look like a self-propelled stroller from the second half of the 19th century.

The symptoms of this problem are difficult to ignore, and it is completely impossible not to notice them, regardless of driving experience. If your car's engine runs on a rich fuel mixture, you will notice a number of unpleasant symptoms:

pops and shots coming from the muffler;
black or gray smoke comes out of the exhaust pipe;
the “Check engine” icon is lit on the dashboard;
when reading, error P0172 is detected;
failures in dynamics - the car seems to stumble;
fuel consumption increases significantly;
In advanced cases, the car may not start at all.

Of course, with such problems the car is almost impossible to operate. Many car owners, especially inexperienced ones, are very frightened by such symptoms and consider this a serious breakdown, the correction of which will be expensive. In fact, everything is much simpler and more prosaic, and long-term ignoring of the problem of a rich mixture can be costly.

What does error P0171 (“fuel supply system too lean”) look like?

The probe monitors that there are 14 parts of air to 1 part gasoline. The amount of air can deviate from this number in any direction, but no more than 30%. As soon as this threshold is exceeded, the driver sees error P0171 on the dashboard.

Rich fuel assembly: concepts

Thus, the composition of the fuel mixture is determined by the ratio of air to fuel. This ratio depends on the volume of liquid fuel supplied to the cylinders. When acceleration occurs, the liquid fuel is intensively saturated with air mass. When this ratio is disrupted, the air/fuel mixture is either rich or lean.

Preparing the fuel-air mixture is a process for which the car's injector is responsible. The injection system prepares mixtures with different oxygen contents, and this is what provides a variety of operating modes for the internal combustion engine. It is the composition of the fuel mixture that allows the car to sharply increase speed while overtaking or overcome an incline.

A rich mixture is a mixture that contains less air than required and more gasoline than required. The burning rate of the rich mixture is reduced, and therefore it burns out already in the muffler. Sometimes such a mixture is symbolically called high-calorie.

There is a mathematical formula that determines at what ratio of atmospheric air to fuel the fuel mixture will be normal, rich or lean. It is believed that the normal ratio is a mixture of 14.7 kg of air and 1 kg of liquid fuel. If the ratio of 14:1 is increased in favor of the air mixture, the fuel mixture will be lean. And, on the contrary, when the ratio is 14:1 in favor of liquid fuel, the mixture will be rich.

Artificial boosting of engine power is ensured by adjusting the fuel supply when the amount of supplied oxygen increases. The car owner’s desire to save on fuel consumption is achieved by supplying more atmospheric air.