P0172: mixture too rich error. Diagnostic code p0172 rich mixture

Error p0172 (p0175) means that the mixture is too rich - that is, over-rich fuel assemblies enter the combustion cylinders.

The main reasons for the formation of rich fuel assemblies

The formation of a rich mixture can be caused by the following reasons:

1. Arising from incorrect operation or incorrect vehicle system settings:

• the result of incorrect settings of the fuel system to reduce fuel consumption;

• incorrect adjustment of the fuel system to increase power.

2. Arising from improper operation of the engine system:

• injectors supply an increased amount of fuel - this is a problem if traces of combustion of the fuel-air mixture are visible on the outside of the injector or on the side of the copper o-ring. In this case, check whether the injector and O-ring are installed correctly;

• the air filter is dirty – the pressure in the cylinders increases if the filter is clogged;

• leaky closure of the air damper - the pressure in the cylinders decreases, which causes disturbances in the internal combustion engine system (consumption increases, power decreases);

• the fuel pressure regulator is faulty - due to incorrect operation of the regulator, the pressure in the cylinders increases or decreases;

• the coolant temperature sensor is broken. It reports incorrect data to the ECU;

• problems with the operation of the throttle position sensor;

• the catalyst does not work;

Depending on the reason that triggered error p0172, problems with the car may be different. For example, fuel consumption will increase or the speed will fluctuate on a hot or cold engine.

Interestingly, almost all errors can be eliminated by adjusting the liquid fuel injection. You shouldn’t delay fixing the problem - the injector may burn out, the spark plugs may burn out, or the pistons may become unusable. It must be said that the problem of a very rich air-fuel mixture is quite common. In car services or workshops, mechanics will solve it quickly and at a low price (depending on the model and service center).

Possible fault location

Most likely, the formation of a rich fuel assembly could be caused by malfunctions of the following elements and systems:

• air intake system;

How does error P0172 manifest itself?

The air-fuel mixture can be over-rich for several reasons, depending on which the behavior of the car will change. So, with error P0172, the car may behave as follows:

• A cold engine will “choke” until it warms up completely;
• The engine will “choke” in a cold and warm state at idle, and the speed will begin to “float”;
• Fuel consumption will increase;
• The car will become less playful.

Symptoms of the P0172 code may occur together or separately from each other.

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.

Error P0172, what should I do?

After identifying and correcting the malfunction that led to the P0172 error, it is necessary to reset the fuel trim. This is required to reset the long-term adjustment.

Consider whether the software settings have been changed. It is quite possible that after “light chip tuning” from a well-known fuel systems engineer throughout the cooperative and reflashing the controller, the engine can operate correctly for some time.

If the malfunction occurs “by itself”, and all the problems listed above do not concern this motor, it is necessary to conduct high-quality computer diagnostics of the engine.

Standards of air in the fuel mixture

The average engine requires approximately 15 kg of air and one kilogram of gasoline for normal operation. If this proportion is shifted towards air, then the mixture is considered lean, if on the contrary - rich.

Can't beat error p2188

year of manufacture 2022, mileage over 170,000 km. 4th generation gas equipment was installed for 10,000 km. Until about 120,000 km, everything worked like clockwork, no checks or errors, until the catalyst fell apart. Instead of a catalyst, a flame arrester was made, but the catalyst error began to occur periodically.

New Lada: Tire pressure in winter for Lada Vesta, Grant, Priora. VAZ 2114/VAZ 2110

It was reset for a few days, when after 327, when it itself disappeared, but after a while it appeared again. I tried to put a fake under the second lambda probe with a piece of catalyst inside, but nothing helped. After a year and a half, succumbing to the persuasion of “major specialists,” I decided to change from Euro-4 to Euro-2.

Since then, P2188 began to pop up constantly.

1. Full maximum of gas. Everything was washed, licked and tested. Conclusion, it works like a clock.

2. Drove it to the service center. We washed the throttle valve, filter, spark plugs and everything that could be replaced. Everything is fire.

But two days later this creature jumped out again. The stitchers immediately gave up, saying that it was because of the gas. The service cleaners also shrug their shoulders and cannot understand anything from the scanner, since there is a memory error. Who cares, they took money for diagnostics, reset the error, but naturally it comes back (I can do this procedure myself via a smartphone and an OBD adapter).

Maybe someone has encountered such a situation. I’m ready to take it to a specialist, but I’m really tired of having to deal with the useless cleaning of spare parts for crazy money. I noticed a pattern that the error occurs more often in wet weather, I looked at the wires, everything seemed to be in order.

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.

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?

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.

The P0172 code is one of the most common that owners of electronically controlled vehicles may encounter. It is often found on cars from the AvtoVAZ plant, as well as on foreign cars - Mercedes, Mazda, Toyota and others. The P0172 code indicates to the driver that the combustion chambers are being supplied with too rich a mixture, causing the engine to malfunction and increasing fuel consumption.

Step-by-step instructions for troubleshooting

Look for its signs. When error P0172 appears, the procedure is as follows:

1. Check spark plugs. The absence of black dense carbon deposits is a direct indication of a malfunction of the lambda probe; measuring the voltage at the output of the oxygen sensor will help confirm this (it should fall during the gas release, when the injection computer cuts off the supply of gasoline to the cylinders).
2. Check the condition of the engine oil in the crankcase.
3. On cars with a mass air flow sensor, check the sensor readings; on others, check the air temperature sensor.
4. Try disconnecting the adsorber from the intake manifold.
5. Measure fuel pressure.
6. Remove the fuel rail with injectors and force the fuel pump to turn on using a jumper between the power contacts of the pump relay. The injector nozzles must remain dry.

How does error P0172 manifest itself?

The air-fuel mixture can be over-rich for several reasons, depending on which the behavior of the car will change. So, with error P0172, the car may behave as follows:

• A cold engine will “choke” until it warms up completely;
• The engine will “choke” in a cold and warm state at idle, and the speed will begin to “float”;
• Fuel consumption will increase;
• The car will become less playful.

General concept

Delving into the concept of what a too rich mixture is (VAZ, Skoda, BMW, Chevrolet, etc.), a few words should be said about the fuel itself. It consists of gasoline (diesel) and air correlated in a certain proportion. Liquid fuel is supplied to the engine cylinders. This ratio largely depends on its quantity.

A rich mixture is one that contains more gasoline and less air than normal. Since there is not enough oxygen inside the combustion chamber, the engine process loses power. Because of this, gasoline burns out already in the muffler. Some auto mechanics call this state of fuel high-calorie.

These violations are reflected in the appearance of the spark plugs. A characteristic black soot appears on them. There may be several reasons for this state of the engine system. They must be found and eliminated.

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;

The ECU receives information from the following sensors:

• Coolant;
• MAP sensor (absolute pressure);
• Camshaft position;
• Crankshaft position;
• Intake air temperatures;
• Throttle position.

• 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.

On which cars is this problem most common?

The problem with code P0172 can occur on different machines, but there are always statistics on which brands this error occurs more often. Here is a list of some of them:

• Audi (Audi a4, Audi a6)
• BMW (BMW X5, F10)
• Cadillac (Cadillac SRX)
• Chery (Chery Amulet)
• Chevrolet (Chevrolet Aveo, Cruz, Lacetti, Orlando, Rezzo, Spark, Tahoe, Trailblazer, Epica)
• Chrysler (Chrysler Voyager, Pacifica, Sebring)
• Citroen (Citroen C4, C5)
• Daewoo (Daewoo Matiz, Nexia)
• Dodge (Dodge Dakota, Intrepid, Caravan, Ram, Stratus)
• Fiat (Fiat Albea, Doblo)
• Ford (Ford Mondeo, Focus, Fusion)
• Geely (Geely MK)
• Honda (Honda Accord, Jazz, Odyssey, SRV, Fit, Civic)
• Hover
• Hyundai (Hyundai Getz, Tucson, Elantra)
• Jaguar (Jaguar XJ, X-Type)
• Jeep (Jeep Grand Cherokee)
• Kia (Kia Rio, Sid, Spectra, Sportage, Cerato)
• Land Rover (Land Rover Range Rover)
• Lexus (Lexus gx470, is250, rx300)
• Lifan
• Mazda (Mazda 3, Mazda 6, Mazda cx5, Mazda cx7, Mazda RX-8, Surname, MPV)
• Mercedes (Mercedes m272, ml350, w164, w203, w204, w211, w212, w221)
• Mitsubishi (Mitsubishi Lancer)
• Nissan (Nissan Almera, Vingroad, Primera, Sunny, Skyline, X-Trail)
• Opel (Opel Astra)
• Peugeot (Peugeot 207, 308, 407, 408, 3008)
• Porsche (Porsche Cayenne)
• Rover
• Saab
• Skoda (Skoda Yeti, Octavia, Rapid, Fabia)
• Ssangyong (Sangyong Kyron, Rexton)
• Subaru (Subaru Outback, Impreza, Tribeca, Forester)
• Suzuki
• Toyota (Toyota Avensis, Allion, Auris, Vish, Gaia, Camry, Corolla, Noah, Prius, Probox, Rav4)
• Volkswagen (Volkswagen Golf, Jetta, Caddy, Passat, Polo Sedan, Tiguan)
• Volvo (Volvo s40, s60)
• VAZ 2107, 2108, 2110, 2112, 2114, 2115
• Gazelle Next
• Lada Vesta, Granta, Kalina, Niva, Priora
• Tagaz Tager
• UAZ Bukhanka, Patriot, 409

With fault code P0172, you can sometimes encounter other errors. The most common ones are: P0106, P0131, P0132, P0134, P0138, P0151, P0170, P0171, P0175, P0300, P0363, P0420, P0501, P2178, P2188.

Why does P0172 - mixture too rich occur?

To understand the reasons for the appearance of error P0172, you need to understand the process of formation of the air-fuel mixture and its combustion. After analyzing it, we can conclude that the mixture may be enriched due to the supply of too much fuel or due to insufficient air supply.

Absolute pressure and oxygen sensors are responsible for supplying air for mixing with fuel.

In addition to improper operation of the sensors, an error with lack of air can occur for the following reasons:

Also, error P0172 can manifest itself due to over-richness of the mixture as a result of poor combustion. This problem may be caused by improper operation of the spark plugs or ignition coils.

It cannot be ruled out that problems with the mixture and its combustion arise due to failure of the oxygen or air flow sensors.

Other signs

Of course, there are many reasons for excessive fuel consumption. But usually the first sign here is code P0172.

There are also a number of other signs of a problem:

• Loud pops are heard from the muffler;
• the smoke coming out of the chimney is black or dark gray;
• power is lost.

Noisy exhaust occurs more often at high speeds. The reason is that the fuel does not burn completely and is therefore discharged along with the gases to the outside. However, in its path there is a muffler that does not allow fuel to pass through, so it accumulates in it and explodes when it reaches a critical mass. As a result, there is a risk of destruction of the muffler itself or the resonators.

Blackish smoke comes out due to the fact that the combustion of gasoline residues occurs in the exhaust system, where the products formed during ignition are not filtered.

The loss of power is due to slow and incomplete combustion of fuel. As a result, it literally floods the candles, which leads to the loss of spark and, accordingly, to an even worse situation. In this situation, the piston does not receive a normal push and a decrease in power occurs.

Under such circumstances, gasoline consumption cannot but increase. The presence of a malfunction in the system does not prevent fuel from flowing into the engine, but it is used there with very low efficiency. A significant part of it is simply thrown into the wind, and in the literal sense.

What to do if P0172 Combustion Too Rich Occurs

To determine the causes of the error, you need to check the information that the diagnostic scanner transmits when simulating the conditions for the error. If you can’t immediately identify the problem, you need to act according to the following scenario:

The mass air flow sensor is checked for chips, damage, oxidation, and loss of contact;

After identifying and correcting the malfunction that led to the P0172 error, it is necessary to reset the fuel trim. This is required to reset the long-term adjustment.

Main reasons

There are several main reasons that cause deviations in the air-to-gasoline ratio. The most basic of them may be deviations in the engine control system, as well as malfunctions of the air damper drive. An injector malfunction may also explain why a rich mixture is detected. If the carburetor is not adjusted correctly, it can also cause deviations. Another factor in the formation of a rich mixture is a clogged air filter.

Often the cause of problems in the fuel system is the wrong actions of the car owner. In order to reduce gasoline consumption or increase engine power, the driver may incorrectly adjust the system. As a result, he gets problems with the engine and the need for extraordinary maintenance or even repairs.

Automatic diagnostic system

If your vehicle's diagnostic system indicates that a "Compound Too Rich" error has occurred, certain actions must be taken. To do this, you need to understand the principles of the scanner.

Air is supplied to the fuel when diagnosing the MAP sensor and lambda probe. Perhaps it is caused by deviations of these particular systems. However, in addition to them, problems may be associated with deviations in thermal clearances (engine with LPG), mechanical damage to sealing materials, insufficient compression or deviation during timing operation.

To understand why automatic diagnostics indicate such an error, the car owner can take several steps. First of all, you need to analyze the information that the scanner provides. Next, you can artificially simulate the conditions for the occurrence of such a malfunction.

The next step could be to check components and mechanisms, such as contacts, absence of suction, as well as the operability of systems related to the supply of fuel and oxygen to the combustion chamber.

What should the fuel-air mixture be?

Under ideal engine operating conditions, the amount of air should exceed the amount of fuel by 14.7 times. That is, for one drop of fuel there are 14.7 “drops” of air. This ratio is called stoichiometric and is most useful in terms of engine efficiency.

A rich mixture is a violation of the “golden” rule. Within certain limits, a slight enrichment can give an increase in power, but everything has a limit, beyond which a malfunction occurs.

How to tell if a mixture is rich

Several characteristic features:

Rare breakdowns

Experts say that 90% of all “Rich mixture” errors are related to injector adjustment. It is not difficult to eliminate it. The main thing is to pay attention to improper operation of the car engine in time.

The rarest and most exotic are considered to be malfunctions of the engine control unit, as well as poor condition of the contacts. Sometimes there are cases of oxygen sensor poisoning. An experienced specialist can identify such deviations. In this case, not every car owner can solve the problem on their own.

Having considered what a rich mixture is, you can understand the danger of such a situation. If unforeseen situations arise, it is better to contact the service center. At service points there is the necessary tool with which you can perform diagnostics. This will save the car's engine.

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). Do chip tuning

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.