Error P0172 or “rich mixture” - the fuel supply system is too rich: reasons, how to diagnose and fix

What does error 0172 mean?

Code P0172, which is issued by the on-board computer, is a system error indicating that the fuel mixture is getting too rich into the combustion cylinders.

An over-enriched mixture is a mixture in which the air content is less than normal, and, on the contrary, there is more gasoline than necessary.

Fuel mixture composition diagram
Theoretically, the error can be ignored, but unstable engine operation will not allow you to use the car normally, so you still have to delve into the problem. An average static engine requires 1 kg to operate correctly. about 15 kg of gasoline. air.

If there is less air, then the mixture is considered rich, and if, on the contrary, it is poor. Of course, the proportions of fuel and air are slightly different in different operating modes of the car, so the ECU continuously monitors this ratio and immediately alerts the driver in case of problems.

Symptoms of code P0172

Depending on the nature of the problem, P0172 may or may not be accompanied by drivability problems. At the very least, you will get better fuel economy because when the ECU is in limp mode, it no longer uses feedback from the sensors to adjust the mixture.

In severe cases, you may notice rough idling, lack of power when accelerating, even misfiring or stalling. Symptoms gradually worsen as the engine warms up.

The worst cases may be accompanied by black smoke from the muffler and a flashing warning light, warning you of possible catalytic converter damage.

You may also smell a strong fuel odor and see black soot on the tailpipe or rear of the vehicle, which indicates that there is a lot of unburned fuel passing through the exhaust system.

When the mixture becomes rich

Deviations in mixture preparation appear as a result of certain failures of vehicle systems. The injector is responsible for the process of creating fuel. It prepares mixtures with a certain percentage of oxygen. It is this ability of the presented engine element that allows the engine to operate in different modes.

If necessary, the driver can, thanks to such a device, increase speed, cope with inclines, overtake, etc.

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The rich mixture at the injector is determined by a mathematical formula. The normal ratio is 14.7 kg of oxygen per 1 kg of liquid fuel. If for some reason the amount of oxygen in this formula increases, this composition is called poor. If the amount of fuel in the mixture rises, the mixture acquires the status of rich.

The car owner can independently adjust the level of oxygen supply to the fuel mixture. Errors made in this process lead to breakdowns and improper operation of the vehicle.

Under what conditions does P0172 occur?

In order for the electronic control unit to diagnose error P0172 and transmit information about it to the driver, it must receive information from a number of sensors. The conditions for displaying a message about over-enrichment of the air-fuel mixture are as follows:

1. The engine is started;
2. Fuel is supplied with feedback from the lambda probe;
3. The ECU receives information from the following sensors:
   Coolant;
4. MAP sensor (absolute pressure);
5. Camshaft position;
6. Crankshaft position;
7. Intake air temperatures;
8. Throttle position.
9. In the test cycle, the average combined early and long term fuel trim values ​​are less than 33% for 3 minutes (or more) of the 7 minutes.

The main signs of the error and for which car brands it is typical

With a rich fuel mixture, engine malfunctions can manifest themselves in the form of:

1. Floating speed;
2. Choking at idle (hot and cold);
3. Increased fuel consumption;
4. Loss of dynamic characteristics of the car;
5. The appearance of black or gray exhaust gases;
6. Loud pops in the muffler - fuel burns out in the exhaust system. Often appear when releasing the gas pedal.
7. Black velvet soot on spark plugs.

All these signs can appear either individually or simultaneously. Ignoring the problem can lead to failure of parts of the cylinder-piston group, spark plugs, and exhaust system elements.

Error p0172 is typical for most domestic cars, for example VAZ 2114, UAZ Patriot, Kalina, as well as foreign cars - Toyota Camry v40, Opel Astra J, Toyota Corolla 150, Chevrolet Lacetti 1.6, Chevrolet Cruze, Skoda Fabia, Subaru, Mercedes, Mazda and others. But the reasons for its appearance are identical for all car brands, so it’s worth dwelling on them in more detail.

Driving a car

A mixture that is too rich also appears when driving. Almost any driver will immediately notice this. The car becomes less dynamic. Engine power decreases sharply. Since the combustion process in the engine chamber occurs more slowly, the mechanism is not able to work at full strength.

In some cases, the car may not even move. But this is with very serious deviations in the ratio of fuel and air in the combustion chamber.

When driving a car, the owner may notice that fuel consumption has increased. This is also a characteristic sign of engine malfunction due to running with a rich mixture. This violation can be explained simply. The engine does not operate efficiently under such conditions. The fuel mixture is not being used correctly. To prevent a low combustion rate, the motor begins to inject more liquid fuel into the chamber.

Reasons for a rich mixture on the VAZ-2114

The formation of a rich fuel-air mixture occurs in a number of cases:

• incorrectly adjusted fuel system. As a rule, this is the result of intervention in the system to reduce gas mileage or increase power;
• air filter clogged. In this case, the required amount of air does not enter the combustion chamber;

A dirty air filter is the most common cause of a rich mixture. If error P0172 is detected, you should first check the condition of the filter.

• incorrectly configured injectors;

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Injector inspection

• high fuel pressure in the rail or malfunction of the pressure regulator;
• air flow meter failure. In this case, the sensor transmits incorrect data to the on-board computer, as a result of which the fuel supply system operates in accordance with these indicators;

New mass air flow sensor

• economizer malfunction.

Fuel supply deviations

Since the process of forming a combustible mixture consists of two main components (gasoline and air), disturbances are possible from the supply side of each of them. Excess fuel is detected much less often than lack of air. But typical fuel supply disruptions should be considered in more detail.

A mixture that is too rich due to fuel system issues can be caused by high line pressure. This deviation is caused by a malfunction of the fuel pump or regulation system. To check this version, use a special fuel pressure gauge.

Deviations in the composition of the mixture can be caused by the adsorber. Due to a malfunction of the vapor recovery system, a large amount of gasoline is released through it.

The injectors may also be faulty. The injector may not be able to hold fuel when closed. This causes it to enter the chamber even when the nozzles are closed.

Air supply faults

The “Rich mixture” error, which is detected by the car’s diagnostic system, is much more often caused by insufficient oxygen supply to the combustion chamber. There are several reasons for this violation.

First of all, the air filter may be simply dirty. For some reasons (severe operating conditions, driving on dirty roads), this element of the oxygen purification system may become unusable even before the time specified by the manufacturer. Therefore, it is necessary to visually evaluate the cleaner. If it is dirty or coated with oil, it must be replaced urgently. Otherwise, the motor will quickly fail.

In some cases, the cause of inadequate air supply to the combustion chamber may be a breakdown of the air flow sensor. This will help identify the scanner readings. Sometimes a faulty air pressure sensor in the manifold system is detected.

How serious is P0172 - Too Rich?

With this error, the car will not pass the emission test. If the fuel content in the mixture is very high, black smoke may come out of the exhaust pipe. In addition, unburned fuel can damage the catalyst. And the most noticeable thing is increased fuel consumption.

Signs of a too rich mixture on a VAZ-2114

If the engine behaves incorrectly and consumes more fuel than it should, there may be many reasons for this. However, the first signal indicating that the power system has a rich mixture will be error message P0172 .

Appearance of a spark plug with an over-rich mixture

In addition, there are a number of symptoms that are immediately noticeable:

1. Strong pops in the muffler , regardless of speed, more often at high speeds. This happens because unburned fuel in the combustion chamber invariably enters the exhaust system along with the exhaust gases. It cannot leave the muffler as easily as gases do, so it accumulates in the labyrinths of the muffler and, when it reaches a certain temperature, ignites or explodes. This is fraught not only with special sound effects, but also with torn or torn off resonators and mufflers.
2. The smoke from the exhaust pipe becomes dark or completely black . This happens for the reason that the fuel burned in the exhaust system is not filtered by anything; more precisely, the gas from the combustion of gasoline in the muffler does not undergo filtration.

Black smoke from the exhaust pipe

Visual inspection of spark plugs

When and how does a mixture become too rich?

Despite the fact that we now blame gasoline for having too much of it, in fact, most often it turns out that the proportion of the mixture is off due to less air.

The first thing to do, and this is the easiest thing, is to check the condition of the air filter. It may simply be clogged, so the required amount of air no longer enters the combustion chamber.

If the filter is obviously clean, then there may be several reasons:

Incorrectly adjusted injectors . They can open and close on time, but the amount of fuel injected may be too large. As a rule, injectors can only be checked on a special stand, as can their cleaning and adjustment. But more often than not, they are simply changed. When replacing, pay attention to the correct choice of injectors.

How to tell if a mixture is rich

Several characteristic features:

• Pops, explosions in the muffler. Excess fuel, unburned as a result of an incorrect ratio, explodes in the hot exhaust pipe;
• Black exhaust and carbon deposits on the exhaust pipe;
• Loss of dynamics. The driver feels as if the car is being held by the bumper;
• Increased consumption. The car tries to compensate for the excess air by adding fuel;
• Rich mixture error "P0172". Read by the scanner when CHECK ENGINE lights up on the panel:

How to diagnose trouble code P0172?

• Checking the fuel pressure in the fuel rail
• Using indicator lights, the voltage pulses of the fuel injectors are checked.
• Vacuum hoses are checked for leaks
• The serviceability of the mass air flow sensor and oxygen sensors is checked
• Checking the patency of the exhaust system

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Lean mixture (injector), signs and consequences

Blend Setting

While the vehicle is moving, the Pilot records the operation of the oxygen sensor and air flow sensor. At the same time, you can see in real time which mixture is lean or rich .

The signs of a poor mixture are a stalling engine, more air than 14.7 g, ignites faster and is accompanied by excess heating. Such a mixture is prone to detonation, at low speeds this is not a problem. At full load, mixture 14 is already considered dangerous. It is not reasonable to make the entire system on a 14.7 mixture. At low speeds this will not be enough for acceleration, and at higher speeds you will simply catch detonation.

A lean mixture has consequences - at high speeds, with full load, the level of detonation reaches catastrophic consequences. Burnout or fusion of the piston, burnout of valves or spark plugs. An increase in temperature and loss of power is the simplest thing that can happen to an engine during detonation. Usually this is a seized and overheated motor.

How to remove error P0172

The test must be done from simple to complex. That is, the simplest thing is to check whether there is air leakage on the intake and exhaust manifolds, then check the spark plugs, spark plug wires (there are often broken wires) and the ignition coil. For a complete check, you also need to check the lambda probe, MAF, and DTOZH sensors with a multimeter. Then check the ignition marks and fuel pressure with a pressure gauge.

After eliminating the found cause, you need to reset the fuel supply adjustment. Typically, P0172 errors are resolved by flushing or replacing the mass air flow sensor and oxygen sensor.

Recommended Tools to Fix P0172

There are several important tools that will help you fix the P0172 trouble code. These tools include:

• Car charger.
• Multimeter.
• OBD-II scanner.
• Pressure gauge.
• MAF cleaner.

What needs to be repaired to resolve P0172?

• Repairing leaky vacuum hoses
• Replacing a faulty fuel injector, fuel pump or fuel pressure regulator
• Replacing a clogged VAZ air filter
• Replacing the thermostat or coolant temperature sensor
• Replacing spark plugs
• Replacing or cleaning the mass air flow sensor and oxygen sensors

How to return the mixture to normal

If the problem is similar to those described above, you should contact a competent diagnostician. Sometimes the cause of a rich mixture can be eliminated by adjusting the throttle valve or injector. In other cases, replacement of “flying” sensors is required. Therefore, a specialist is needed who has the knowledge, experience and equipment to conduct a comprehensive diagnosis.

Chip tuning can eliminate problems with the oxygen sensor (lambda) - this is one of its functions. When choosing this solution, trust the professionals to reprogram the control unit (ECU).

Codes related to P0172

When diagnosing trouble code P0172, you may also encounter other errors:

• P0170 - the fuel-air mixture ratio is impaired, bank 1.
• P0173 - the fuel-air mixture ratio is impaired, bank 2.
• P0175 - mixture too rich, bank 2.
• P0101 - The air flow sensor output signal is out of range.
• P0104 - intermittent signal from the mass air flow sensor.
• P030x - Cylinder misfire is random or specific.
• P0171 - mixture too lean, bank 1.
• P0174 - mixture too lean, bank 2.

How to save gasoline using an injector in simple ways

The simplest and often very effective way to reduce fuel consumption is to clean the injector, since contamination disrupts the correct shape of the spray pattern. At the same time, due to the delay in gear shifting, the dynamic acceleration characteristics of the vehicle also change.

Similar preventive measures include cleaning a clogged air filter. It affects the reliability of the data transmitted to the electronic control unit and indirectly affects the calculation of specific gasoline consumption at a given load.

Malfunctions in the operation of the catalyst lead to the fact that it resists the release of exhaust gases. This leads to insufficient discharge in the exhaust manifold, and this, in turn, leads to the transmission of distorted information about the increased load. The system, reacting to the supposedly increased load, increases the fuel supply, excessively enriching the air-fuel mixture. Failure of the catalyst is caused by using gasoline of worse quality than recommended by the manufacturer. Therefore, the advice to comply with fuel quality requirements is one of the first and most widespread.

While the vehicle is moving, the Pilot records the operation of the oxygen sensor and air flow sensor. At the same time, you can see on the computer monitor in real time which mixture is lean or rich.

Content

Expert advice

If the mixture in the fuel tank is too rich, the first thing experienced auto mechanics recommend doing is resetting the additional settings for the injector. If the owner independently adjusted the fuel control system, he could make serious mistakes. A rich fuel mixture will lead to inevitable engine failure very soon.

If the cause of the deviation is related to the injector system, this can be determined visually. With such a malfunction, traces of fuel combustion appear on the outside of the injector.

Burnt and soot can also be found on one side of the copper O-ring. Such deviations are caused by incorrect installation of the injector. If the O-ring is not in its place, similar malfunctions are also possible.

Sources

• https://adact2.ru/a/prichiny-bogatoy-smesi-na-inzhektore
• https://remontvazov.com/oshibka-0172-na-vaz-2114
• https://elm3.ru/diagnostika/oshibka-p0172
• https://FB.ru/article/283131/slishkom-bogataya-smes-prichinyi-i-sposobyi-ustraneniya-ot-professionalov
• https://okeydrive.ru/oshibka-p0172-slishkom-bogataya-smes/
• https://AutoTopik.ru/diagnostika-neispravnostei/1598-r0172.html
• https://autotime.net.ua/oshibka-p0172-vaz-slishkom-bogataya-smes/
• https://autostuk.ru/oshibka-r0172.html

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