Error 171 mixture too lean

The reasons for this error are in many ways a mirror image of the reasons for the appearance of error P0172 in the controller memory.

A lambda probe that degrades over time may physically stop working - that is, deviations in the oxygen balance “from different sides” of the sensitive element will no longer lead to a change in voltage at its terminals (here we are talking about the classic version of a platinum oxygen sensor, which is precisely the source of voltage). For the ECU, this is equivalent to a constantly lean mixture; accordingly, the “fuel supply correction” parameter will begin to constantly go positive.

How to find an air leak

First method. It is the simplest, it allows you to find out whether there are any air leaks at all and does not require absolutely any equipment. All we need is just the key for “10”. You need to unscrew the mass air flow sensor from the air filter and pull it out together into the corrugation.

Now we start the engine and, using the palm of our hand, completely block the air inlet into the intake manifold through the mass air flow sensor. The corrugation should shrink from the vacuum and after a couple of seconds the engine will stall. We don’t let go of our hand and listen for where things hiss—this is an extra air leak (more details in the video below).

Second way. Here we need some kind of flammable liquid - gasoline, ether, WD-40, carburetor cleaning fluid, etc. It is best, of course, to use gasoline or ether, they are more natural for engine operation. We fill a syringe with gasoline or take a can of any of the above liquids and spray all the connections of the intake manifold. If any of the connections are not sealed, then the liquid will definitely get inside the manifold and the engine speed, at the same time, should change (either decrease or increase). If the engine does not react in any way, then the connection is sealed, there are no problems with it and you need to look further. Well, if the engine starts to react, consider half the job done. We change the gasket or hose and rejoice that error P0171 has disappeared.

The third method is to use a smoke generator. If you don’t have such a thing in your garage, you can ask your friends for it or make it yourself. There are many options for making smoke generators on the Internet. I chose the simplest and fastest - a smoke generator made from a regular cigarette.

How serious is code P0171?

The P0171 code is a serious problem. If this error is stored in the ECM, then the car's engine will not maintain the correct air to fuel ratio. While driving there will be a loss of power and increased fuel consumption. In order for the car to work normally, the malfunction must be eliminated as soon as possible. Incorrect engine operation over a long period of time can lead to more serious malfunctions that will require much more money to eliminate.

Source

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.

Video "Lean mixture"

On-board computer error P0171 means that the fuel mixture is too lean. Those. the amount of air supplied does not correspond to the amount of gasoline supplied. As a result, part of the gasoline does not burn in the combustion chamber, but burns out in the manifold or exits through the exhaust system.

Some of the symptoms that accompany error P0171:

The engine shakes and jerks
Increased fuel consumption
The car stalls
Weak engine thrust

Air leak

First of all, check the air leak after the mass air flow sensor. Check how tightly all clamps are tightened. Check connections with soapy water. Air leaks will give themselves away as air bubbles in the solution. If there is a strong air leak, you will hear a characteristic hissing sound.

A good article on how to find an air leak: https://www.drive2.ru/l/10216700/

Mass air flow sensor

If no air leaks are observed, check the air flow sensor (MAF). For information on checking the sensor, read the article How to check the mass air flow sensor. The easiest way to diagnose in case of error p0171 is to disconnect the mark from the sensor while the engine is running. If immediately after switching off the engine operation has leveled off, the engine does not twitch and responds well to gas, it’s time to replace the mass air flow sensor with a new one.

MAP pressure sensor

The pressure sensor can also cause message P0171.

Check the connection of the contacts to the sensor.
Check the contact for ground.
The ideal option is to temporarily install a working MAP sensor from another car.

Intake manifold

Make sure that there are no cracks, chips, or missing sealant in the intake manifold where air can get in.

Fuel system malfunction

Check the pressure in the fuel rail at a service station, check the fine filter from the fuel pump.

Mixture too lean

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 even is. This is important only because such a reason can lead to expensive repairs to 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

To ensure a successful engine start, it is necessary to mix the fuel and air mixture in ideal proportions; this is what the injector is responsible for.

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 readings are equal. The main reasons for a lean mixture

The main and most important symptom that the system has a lean mixture is a stalling or unstable engine. And if the mixture is very poor, then it is possible that it will not start at all.

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?

One of the fundamental checks for the condition of the mixture will be to assess the condition of the spark plug.

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.

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:

Dirt has entered the sensor that takes into account air flow, causing the measurement to be incorrect.
There has been a leak in the EGR valve, which is responsible for recycling exhaust gases in the engine. The valve began to close poorly, as a result, excess air began to flow into the intake manifold.
The EGR differential pressure sensor is faulty, resulting in more air flowing through the EGR valve than required.
One or more vacuum leaks have occurred.
There were problems with the fuel pump, due to which its power decreased significantly.
The fuel injectors are clogged.
The fuel pressure regulator has lost its seal.
The air flow sensor is faulty.
The oxygen metering sensor is faulty.

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.

Clogged injectors

If you do not change the fuel elements of the car system on time, a lean mixture may form on the injector, the reasons for which will lie in the incorrect operation of the injectors. That is, fuel is supplied, but supplied in fairly low quantities. An injector is a special device related to the injection system of a car. There are many elements: electromagnetic, electrohydraulic or piezohydraulic. Vehicles with gasoline engines use electromagnetic parts.

To solve the problem, you can restore the previous injection by washing the injectors, which is carried out only using special equipment.

By the way, to avoid contamination of fuel filters and injectors, you should clean the fuel tank at regular intervals, since there is a large accumulation of dirt, sand or other substances there.

Elimination method

It usually consists of three large stages:

Checking fuel sensors.
Checking the fuel system and injectors.
Check the tightness of all hoses and manifolds.

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.

Fuel system malfunction

Other causes of a lean mixture on the injector are due to improper operation of the vehicle's fuel system. As a rule, operational disruptions occur due to low-quality fuel, which is filled at little-known gas stations. One of the options for unstable engine operation and the formation of a lean mixture is clogged fuel cells of the car. In such cases, there is a misfire in 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 into the fuel pump. The second element is most often located near the tank on the bottom of the car, less often in the engine compartment. To avoid over-leaning 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.

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:

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.

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

Idle speed sensor (although it would be more correct to say regulator).

The IAC sensor is located on the throttle valve

Throttle position sensor.

Throttle position sensor

Oxygen 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.

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

Poor or intermittent operation of the fuel pump. For treatment, it is necessary to dismantle the product, carry out diagnostics and, if necessary, replace the element with a new one.

Checking the fuel pump by immersion in water

What to do if there is an error

The causes of a lean mixture on the injector (including VAZ 2110), if detected, can be eliminated independently, but the best solution would be to take the vehicle to a specialized workshop, where auto mechanics will carry out high-quality diagnostics and will be able to detect other malfunctions in the operation of 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 air-fuel mixture being created. As a rule, on injection engines and carburetor engines, the car owner has this opportunity. An example is adjusting the throttle opening angle. To do this, it is enough to change the position of the locking ring, alternately moving it along the special grooves of the damper.