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

In addition to direct malfunctions of the car that prevent it from being used at all, there may also be minor problems, which, however, can be very difficult to eliminate. For example, this applies to an error that is designated P0171 or simply 0171 .

Causes of a lean mixture

The error shows that the mixture is lean.
How can we 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:

The reason lies in the electronic control unit.
Sensors and electrical equipment.
Fuel system.
Throttle valve and air filter.
Ignition system.

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.

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.

Mass air flow sensor

The IAC sensor is located on the throttle valve

Throttle position sensor

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:

The filter mesh in the module is clogged. To eliminate the problem, you need to replace the element with a new one.

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:

Spark plug . This part requires a comprehensive check, namely: checking the gap between the electrodes, resistance diagnostics, visual inspection for damage, clogging and cracks. If damaged, replace.

Characteristics of different spark plugs

Injector problems

You don't have to be an expert to understand that the problem here lies in the operation of the injector. And first of all, before we start studying lean mixture, let’s try to find out what it is

This is important only because such a reason can lead to expensive repairs for the car.

Why do jerks happen?

The presence of jerks while the car is moving is a problem that directly or indirectly indicates the presence of problems with the engine, or more precisely, a loss of power. In total, there are two features that affect the development of power in the engine - fuel supply and the ignition system.

If with the ignition, everything is more or less clear, due to the inspection of the generator, spark plugs, ignition wires for faults, and the battery for charge, then in the case of the ignition system everything looks much more complicated.

High voltage wires are marked with arrows

Inspecting the condition of the spark plugs

It happens that when mixing these proportions, a malfunction occurs, and the mixture turns out to be rich or lean.

A clear example of the air-fuel mixture ratio.

In order for the car to obtain maximum power when burning fuel in the cylinders, it is necessary to bring its indicator to the level of 0.85 - 0.9, when excess oxygen = > 1 (at this indicator, gasoline burns completely without residue - approx.), and when there is a lack of oxygen and the reading is < 1.

The main reasons for a lean mixture

The cause of these problems is most often a clogged air filter (see “replacing the air filter”), clogged injectors, wear in the fuel pump, and there may also be air leaks into the system. All these reasons are, one way or another, related to the stable operation of the engine.

What do spark plugs tell us?

So, a light brown tint will indicate that the system is operating normally, a too dark tint will indicate a lack of (enriched mixture - approx.), too light, an excess (depleted - approx.) mixture.

Candles with different types of soot

Please pay attention to the fact that if, in the presence of such malfunctions, the throughput decreases by at least 10-15%, this may lead to further failure of the oxygen sensor (lambda probe, if equipped - approx.), or worse, lead to increased detonation. And this, as you can already understand, will directly affect the performance of the motor.

You can change the readings of engine performance characteristics by cleaning the injector (nozzles), provided that the ignition elements are working properly

And this, as you can already understand, will directly affect the performance of the motor. You can change the engine performance readings by cleaning the injector (nozzles), provided the ignition elements are working correctly.

Diagnostics of the throttle valve block on a VAZ-2114

If you have never performed such a procedure, then first of all you can be advised to inspect the condition of the throttle valve for carbon deposits and other deposits, because fuel vapors coming from the intake manifold settle precisely in this place, accumulating over time.

And the already deposited carbon deposits prevent the damper from closing completely, allowing more air into the system, thereby changing the composition of the mixture - making it leaner. Since large traces of carbon deposits can be detected visually, cleaning should be done with a regular carburetor cleaner, sold in cylinders of different capacities.

We dismantle the throttle assembly

How to clean the injector yourself!

If you do not want to take your car to a specialized workshop to clean the injector, then you can handle this on your own. This work can be carried out both on the removed mechanism and directly on it.

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

On which cars is this problem most common?

The problem with code P0171 can occur on different machines, but there are always statistics on which brands this error is most often present. Here is a list of some of them:

Audi (Audi a3, Audi a4, Audi a6, Audi q5)
BMW (BMW X3, BMW X5, E39, E46, E53, E60, F10)
Cadillac (Cadillac SRX)
Chery (Chery Amulet)
Chevrolet (Chevrolet Aveo, Camaro, Captiva, Cobalt, Cruz, Lacetti, Silverado, Spark, Trailblazer, Epica)
Chrysler (Chrysler Voyager, PT Cruiser, Sebring)
Citroen (Citroen C4)
Daewoo (Daewoo Gentra, Lanos, Matiz, Nexia)
Dodge (Dodge Caravan, Ram, Stratus)
Fiat (Fiat Albea)
Ford (Ford Galaxy, Kuga, Maverick, Mondeo, Taurus, Focus, Fusion, Expedition, Explorer, Escape, F-150)
Honda (Honda Accord, Pilot, SRV, Fit, Civic)
Hover
Hummer H3
Hyundai (Hyundai Getz, Santa Fe, Sonata, Tucson, Elantra)
Infiniti (Infiniti fx35)
Isuzu (Isuzu Rodeo)
Jaguar
Jeep (Jeep Grand Cherokee)
Kia (Kia Carnival, Rio, Sid, Sorento, Spectra, Sportage, Cerato)
Land Rover (Land Rover Range Rover, Freelander)
Lexus (Lexus gx470, ls430, lx470, rx300, rx330, rx350)
Lifan (Lifan x60)
Mazda (Mazda 3, Mazda 6, Mazda cx5, Mazda cx7, Demio, Premasi, Tribute, Surname, MPV)
Mercedes (Mercedes w203, w211)
Mitsubishi (Mitsubishi Outlander, Galant, Delica, Lancer, Montero, Pajero)
Nissan (Nissan Avenir, Hell, Almera, Bluebird Silphy, Vingroad, Beetle, Qashqai, Cube, Maxima, March, Micra, Murano, Note, Primera, Sunny, Serena, Teana, Tiida, X-Trail)
Opel (Opel Antara, Astra, Vectra, Zafira, Insignia, Corsa, Meriva, Mokka)
Peugeot (Peugeot 207, 307, 308, 408, Partner)
Pontiac (Pontiac Vibe, Montana)
Ravon (Ravon P4)
Rover
Saab
Seat
Skoda (Skoda Yeti, Octavia, Superb, Fabia)
Ssangyong (Sangyong Kyron)
Subaru (Subaru Outback, Impreza, Legacy, Tribeca, Forester)
Suzuki (Suzuki Vitara, Grand Vitara, Ignis, Liana, Swift, sx4)
Toyota (Toyota Avensis, Auris, Vitz, Vish, Ipsum, Camry, Corolla, Land Cruiser, Matrix, Passo, Platz, Prado, Prius, Rav4, Celica, Sienna, Tundra, Fielder, Funcargo, Highlander, Estima, Yaris)
Volkswagen (Volkswagen Bora, Golf, Jetta, Caddy, Passat, Polo Sedan, Touareg, Tiguan)
Volvo (Volvo s40, s60, s80, xc90)
VAZ 2107, 2109, 21099, 2110, 2112, 2114, 2115
Volga Cyber
Gazelle
Lada Vesta, Granta, Kalina, Largus, Niva, Priora
Tagaz Tager
UAZ Bukhanka, Patriot, 409

With fault code P0171, you can sometimes encounter other errors. The most common ones are: P0100, P0106, P0130, P0131, P0132, P0134, P0137, P0172, P0174, P0175, P0300, P0302, P0303, P0327, P0420, P0422, P0441, P1101, P1130, P201 5, P2187, P2195, C1201 , U1001.

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 excess air

If, after carrying out this work, instability is also observed in the operation of the system, pay attention to possible places where excess air occurs, since it also affects the leanness of the mixture and the main reasons lie in the following:

Presence of dirt or marks on the mass air flow sensor.
Presence of air leaks, i.e. vacuum leak.

And in order to eliminate the above reasons, it is necessary to conduct a thorough diagnosis.

Troubleshooting

Mass air flow sensor - the air flow sensor can become clogged due to natural reasons, as well as from vapors that come from the throttle valve while the car is not running. And then, over time, accumulating in a thick layer on the thin thread of the sensor, forcing it to send inaccurate data to the ECU, which in turn negatively affects the parameters of air flow and flow into the system.

When diagnosing its malfunction, it is best not to rush into purchasing, since it costs a lot of money, but it is best to check its performance on a known working device. And when it is established that the reason lies in it, then you can try to clean it, or then replace it with a new one.

Vacuum leak

Vacuum leak - these words mean any form of air leaks, i.e. suction into the system, primarily through the manifold gasket or hoses.

The vacuum pump and return hose may cause

Pay attention to the condition of the pipe leading from the air filter to the throttle valve, and the hoses that go to the crankcase ventilation. There should be no visible damage to them, as well as large cracks through which excess air could enter.

In addition to all of the above, you can check the engine oil dipstick and the oil filler cap on the neck, because if these connections are not completely closed, they can cause the appearance of that same excess air.

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.

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.

New Lada: How to connect a radio so that it works without ignition

How to diagnose P0171?

Since the P0171 trouble code means the vehicle is running lean, it can be caused by many different sensors or faulty parts.

This guide is about how to fix the P0171 code the fastest way and what an experienced mechanic will do to find the problem. When performing these steps, you may need some tools to quickly and effectively troubleshoot problems. But you can do without them, try following the instructions.

1. Connect the charger to the car

The first step you should always take when diagnosing a car. You will often turn on the ignition while troubleshooting, and the vehicle voltage should not be low.

Low voltage may cause other unrelated trouble codes. In rare cases, low voltage can even damage electronics, so always use a charger when diagnosing.

2. Check all sensor parameters using an OBD2 scanner

If you have an OBD2 scanner, you can check all sensor parameters. Just check the values of the MAF, coolant temperature, boost pressure, intake temperature sensors and make sure the values are correct.

Many scanners have tables of base values that should be displayed at certain speeds and temperatures. Also, check the oxygen sensor parameters and make sure they are correct. Replace faulty sensors, clear error codes and try again.

You can also do it the old fashioned way and measure all the sensors with a multimeter. This will take a very long time and you have to find which values are correct. If possible, we always recommend using an OBD2 scanner.

3. Check for other fault codes

If you have measured all sensor parameters and are satisfied that they are correct, check for other stored and associated fault codes in the controller. They can tell you where to start your search.

Many problems with sensors occur periodically. When you check them, you get normal parameters, but while driving they may not work correctly and cause a P0171 code.

The control unit is smart. It recognizes the faulty value in just a second and this triggers a fault code. These are the trouble codes you should be looking for. If you receive another error code from any sensor, you need to start checking with the corresponding part of the car first. This can save a lot of time.

Check for inlet leaks

Air leaks are a common problem when it comes to the P0171 code. Leaks in the intake manifold/vacuum hoses/turbocharger can fool the MAF sensor and cause the mixture to lean.

The mass air flow sensor measures all the air entering the engine and reports this amount to the controller. The ECU then injects fuel into the engine depending on the amount of air. A leak can distort this value, resulting in a lean mixture.

The easiest way to find a leak is to use a smoke generator. They, unfortunately, are quite expensive for the car enthusiast. You can make a smoke generator yourself.

Video on how to find air leaks at home without a smoke generator:

And one more piece of advice. You can use a flammable spray like Quick Start or brake cleaner. Spray around the intake while the engine is idling. If the RPM increases, there is a leak in the spray area. For the same purposes, you can use a soap solution.

An air leak can often be found in the PCV valve, especially on VAG vehicles such as Audi, Volkswagen, Seat and Skoda. If you have one of these cars, check the PCV valve under the intake manifold or on top of the engine on newer 2-liter engines.

PCV valve

You should also check the EVAP valve, which controls fuel gases. A leaky or faulty EVAP valve can cause a lean mixture. You can test this valve by blowing through it to see if it is closed or not when it should be.

The problem often occurs in the hose between the intake manifold and the fuel pressure regulator. This causes low fuel pressure and sets the P0171 code.

Check fuel pressure

Low fuel pressure is a common occurrence with the P0171 code. Troubleshooting this problem can be quite difficult because you often check the fuel pressure only at idle. Low blood pressure can occur in other situations. This is usually solved by connecting a pressure gauge.

Many cars have a fuel pressure sensor that allows you to monitor the pressure while driving. But the problem is that this sensor may also be faulty. In this case, the controller will show a low fuel pressure error.

In any case, you need to check the fuel pressure at idle. This may indicate a faulty fuel pump or fuel filter. To check, you will need to connect a pressure gauge to the fuel line.

You should find out what pressure your car has. Disconnect the vacuum hose between the intake manifold and the fuel pressure regulator to obtain the correct value. You can ask a partner to rev the engine to see if the fuel pressure drops.

6. EGR check valve

An open EGR valve when it should be closed can fool the air flow sensor and cause a lean mixture. Checking the EGR valve can be a challenging task. This usually requires removing it or using a smoke generator.

Many OBD2 scanners have an electronic EGR test function. They check the air entering the engine as it opens and closes. This can often help locate a faulty EGR valve because the test will give a positive or negative result.

The ECU often recognizes faulty EGR valves and stores a fault code stored in the controller's memory, but not in all cases. So it's better to double check it. Faulty EGR valves causing P0171 are common on Opel engines. Clogged EGR lines on Opel engines can also cause this.

Here is a video on how to check the EGR valve:

Checking air leaks at the outlet

Air leaking into the exhaust system in front of the oxygen sensors can fool them and cause code P0171. To check for this, the easiest way is to start the engine and listen carefully for any leaks in front of the O2 sensors.

You can have someone plug the exhaust pipe to create pressure in the exhaust system. If you have a smoke generator, everything is even easier. Simply connect it to the rear exhaust pipe and check for smoke from potential leak areas.

It could also be the oxygen sensor that is causing the P0171 code, but this is something you should have already checked in the previous diagnostic steps.

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).

Diagnosis and problem solving

A dirty MAF sensor can skew air intake measurements and therefore skew fuel injection calculations. Next, check the fuel pressure to make sure it is in the correct range. Excessive pressure, due to a faulty pressure regulator or a compressed line tube, will cause more fuel to be injected than the ECU expected.

Check that the ECT and IAT (inlet air temperature) readings are correct. The ECU can pick up blocked sensors, so it's good to check that the ECT and IAT readings are within the normal range.

For example, if the engine is running for half an hour on a hot day, the ECT should show a temperature of about 80°C. If it still reads 0°C, the ECU will richen the air/fuel mixture to compensate, resulting in a rich condition.

Reduced fuel pressure

With the engine running, record the fuel pressure, and then stop the engine. Fuel pressure may drop slightly but should remain stable for at least 10 or 15 minutes.

If fuel pressure continues to drop, you may have a leaking fuel injector, which will result in a rich and possibly non-ignitable condition.

Valve blocking

A faulty valve in the cylinder head dumps unburned fuel into the exhaust gas stream. Check and correct this problem before attempting to correct a rich air/fuel mixture error.

Pay attention to other trouble codes that may be present at the same time as P0171. For example, for VVT (variable valve timing) or ignition system

Traffic fumes

Check the exhaust system for leaks, especially in front of the first O₂ sensor. Damage can be mechanical, in the form of cracks, or caused by corrosion.

The entry of atmospheric air before this sensor can distort the oxygen content measurements. At the same time, the ECU will try to compensate the mixture and add fuel.

Carrying out an inspection

Speaking about the lack of fuel, there are also three main reasons.

The first includes problematic operation of the fuel pump, when it does not have enough power or it does not work as it should.
Next comes the non-optimal resistance of the fuel filter.
Well, the third reason will be a leak that may occur in the pressure regulator. Also, the breakdown may consist of simple contamination of the fuel injectors.

Sometimes we may need to check almost all possible causes in order to find exactly the one that is typical for our case.

Checking the MAF sensor using a multimeter (video)

Therefore, the first thing you need to do is check the sensors. As you may know, one of the most common problems is a clogged sensor, which is responsible for controlling air flow. If too much dirt has accumulated on its wire, this may cause the response to changes in air flow to become too slow.

It can also be contaminated by fuel vapors that pass through the intake manifold and through the throttle body when the engine is not running. These pairs can deposit a special layer of paraffin on the sensor wire, which will send data to the system about the incorrect proportion of the mixture.

What happens next is that the engine control unit cannot add fuel when the amount of air is too high. And after that, an error code will appear on the sensor screen indicating a lean mixture.

False errors P0100 and P0102

It also happens that along with the indicated error, other codes appear, like p0100 or p0102, by which you should definitely know that the problem lies in the sensor. To solve this problem, you need to clean the sensor. To do this, use specialized means for cleaning electrical appliances or the so-called carb cleaner, which is evenly sprayed onto the element that needs to be cleaned. But, still, the best option would be to install a new sensor.

“Vacuum” leak (video about checking for air leaks)

Also, be sure to check the system for vacuum leaks. Depressurization can occur in any part of the inlet pipeline. But this can also happen at the outlet of the throttle body, namely at the place where the vacuum-type hoses and the intake manifold are connected. In addition, depressurization can even appear in places such as the throttle body gasket and the intake manifold.

Checking the fuel system (video)

And, of course, it wouldn’t hurt to check the fuel system. First of all, it is necessary to monitor the performance of the injectors, which is carried out exclusively on a special stand. Most problems with injectors occur due to low-quality fuel; in this case, flushing the injectors will help.

Next, you need to check the fuel pressure, as well as the performance of the gasoline pump, if present. You also need to check the voltage on it.

Among other things, pay attention to the fuel pressure regulator and the fuel filter, as they must be in good working order so as not to cause a lean mixture.

Search for air leaks from a smoke generator

For a smoke generator from a cigarette we will need:

empty 1.5-2 liter bottle
bottom from the same bottle
knife
drill with 5-6mm drill bit
a couple of cigarettes
old bicycle camera
hose from the brake booster (or similar).
pump or compressor

I explain in detail how to assemble all this into a finished structure in the video below. We connect a ready-made smoke generator instead of a vacuum amplifier and begin to pump smoke into the intake manifold, simultaneously checking all the connections and hoses to see if smoke is coming out of them. The appearance of smoke indicates a leaky connection and, accordingly, a possible air leak.

Also, separately from the intake manifold, you should check the vacuum brake booster and the adsorber valve. It is quite easy to check the vacuum seal - just disconnect it from the intake manifold, install a plug and see if there are any changes in the operation of the engine. If it starts to work smoothly and well, then the problem is in the vacuum seal - you need to check the hose itself; if it is intact, we buy a new vacuum seal.

The adsorber valve can be checked just as easily - we disconnect the hose from the throttle assembly and blow into it - it should not blow, i.e. the valve should be closed. If it blows, the valve must be replaced.

We figured out the main reasons for air leaks. Now the second point - LOW fuel.

The first thing to check here is the pressure in the fuel rail. It should not be lower than 3.8 kg/cm2 at XX. If it is lower and when you change the gas it drops even lower, this means that the fuel pump has “died”. In such a situation, you need to replace it and see what happens. Also, check the condition of the mesh and fuel filter. In general, it is advisable to change the filter every 10,000 km along with an oil change.

The second is clogged injectors. Through clogged injectors, less fuel may enter the cylinder than is needed for normal operation. In this case, we wash the injectors, and at the same time it is better to immediately blow out the entire fuel system and replace the filter so that the remaining dirt does not get into the injectors again.

These are all the main reasons for the appearance of error P0171 lean mixture. By checking each of them in turn, you can fix the problem yourself.

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.

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...

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.

If you find an error, please select a piece of text and press Ctrl+Enter.

Error "Lean mixture"

Error on the on-board computer screen

This is a lean mixture error.

Video on lean mixture and fuel economy from “ICE Theory”

A similar problem appears in a situation where the engine takes in a significant portion of air from the atmosphere for one of many reasons. Also, the problem may lie in insufficient fuel injection due to clogging or other problems.

Symptoms and behavior of the car with such an error

This phenomenon can lead to misfires, as well as delays that occur in the car’s response to pressing the gas pedal. The car may start to stall or stall at stops (idling).

In addition, when accelerating, a noticeable twitching is felt, and dips are observed during idle.

Well, the engine itself changes its sound, starting to work extremely unstable. In those engine monitoring and control systems that support Euro 2 and higher standards, there is a lambda probe. It is he who is responsible for controlling the quality of the mixture. It is optimal if there are about 14.7 parts of ordinary atmospheric air per part of fuel.

How does a car behave with a similar problem?

If the engine receives too lean a mixture, this can cause the car to begin to “chop” at idle, and also overheat, since the rate of combustion of the mixture becomes much lower. If you listen closely, you may hear popping noises in the intake manifold. The revs pick up extremely slowly under load.

A lean mixture can be recognized by deposits on the spark plugs.

Burnout of valves and piston system

In the most difficult situations, if the engine overheats very much, this can lead to burnout of the valves and piston system, which entails serious costs for further maintenance and repairs.

A burnt valve will require serious financial investment in car repairs.

High fuel consumption

If a car is used for a long time with such a problem, this can lead to very high fuel consumption, which occurs due to a slow increase in speed. So, drivers have to operate their car in lower gears more often. A lean mixture can occur when the supply balance of its components is upset.

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.

Age: 2022 years old

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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.