What does the error code too rich mixture p0172 mean and how to fix it

Error p0172 means too rich mixture (or system too rich). Thus, a re-enriched fuel mixture is supplied to the combustion cylinders. Like the P0171 code, the rich mixture fault is systemic. That is, it does not indicate an obvious malfunction of the sensors, but the fuel quantity parameters exceed the limit value.

OBD II Diagnostic Trouble Code (DTC) P0172.

Depending on the reason that caused the appearance of such an error code, the behavior of the car can also be different. In some cases, noticeable fuel consumption will appear, and in others, only choking at idle or floating speed either on a hot engine or when it is still cold.

Error conditions

The engine must be started and the fuel supply occurs with feedback from the oxygen sensor (lambda probe), and there is no error from the coolant sensor, intake air temperature sensor, absolute pressure (MAP - sensor), DPPV, DPKV and throttle position sensor. When the average total values of short-term and long-term fuel trims are less than 33% for just over 3 minutes out of the 7th test period. The indicator light on the instrument panel will go out only if the diagnostics does not detect a failure after three test cycles.

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).

You can often hear from a diagnostician “you have a rich mixture.” For an unprepared car enthusiast it sounds mysterious and alarming. Let's figure out what a “rich mixture on an injection engine” is and how bad it is

Possible causes of error p0172

To understand what causes the rich mixture error, you need to make a list of reasons for yourself using a small algorithm:

Enrichment of the mixture occurs due to incomplete combustion (excessive supply or lack of air):

when the fuel does not burn, it means the spark plugs or coils are not working well;
when it is supplied in excess, the oxygen sensor or injectors are to blame;
There is not enough air - the air flow sensor gives incorrect data.

Excess fuel can rarely happen, but lack of air is a typical problem. Air is supplied to the fuel through the connection between the MAP sensor and the lambda probe. But in addition to sensors, the problem can also be caused by a violation of thermal clearances (engines with gas turbochargers), mechanical damage to various gaskets and seals, irregularities in the timing belt or insufficient compression.

To deal with all possible sources that caused the failure, the check is carried out on the following points:

Analyze information from the scanner;
Simulate the conditions for the occurrence of this malfunction;
Check components and systems (presence of good contacts, absence of suction, operability) that may lead to error p0172.

Based on all of the above, we can determine the main reasons:

Mass air flow meter (mass air flow meter), its contamination, damage, loss of contact.
Air filter, clogged or leaking air.
Oxygen sensor, its malfunction (degradation, damaged wiring).
The adsorber valve, its improper functioning affects the capture of gasoline vapors.
Fuel rail pressure. High pressure may be caused by a faulty pressure regulator or a damaged fuel return system.

Search for air leaks from a smoke generator

For a smoke generator from a cigarette we will need:

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.

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 spark plugs, voltage wires and coils. Measure the fuel pressure with a pressure gauge. Check the ignition marks. And also check the connections at the air inlet and exhaust manifold for air leaks.

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.

Author: Ivan Matieshin

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.

Causes of a mixture that is too rich

A mixture that is too rich is usually produced for reasons such as:

Incorrect fuel system adjustment . This may be the result of unqualified intervention or attempts to reduce gasoline consumption or increase the power of the power unit.
Incorrect ECU firmware . This may also be a sign of an inexperienced specialist or the owner’s desire to make the car more powerful and more economical.
Clogged air filter . Some owners forget to change this element during scheduled maintenance or carry out this activity too rarely. Maintenance should be carried out strictly according to the regulations. Otherwise, this can lead to serious problems with engine operation. It is easy to notice that the filter is dirty by visual inspection.

Incorrect injector settings or contamination . Injectors can become dirty due to time and poor quality fuel. They should be cleaned regularly with chemicals or ultrasound. You can do chemical cleaning yourself. Inspecting the injectors will help determine contamination.

Failure of the mass air flow sensor. Checking the part will help identify the problem. You can replace it yourself. But sometimes mass air flow sensors are sold already defective. Therefore, even after replacement, its serviceability should be viewed critically and another part should be taken for checking.
Increased pressure in the rail or failure of the pressure regulator . Replacing the regulator will help solve the problem.

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.

Symptoms of error P0172

The error code P0172 displayed on the on-board computer or during diagnostics with a scanner is often accompanied by the following symptoms:

Increased gasoline consumption. The driver has to refuel more often, and the fuel is enough for less kilometers. Sometimes the increase in consumption is very sharp and noticeable;
Reduced motor power. The engine does not pull, the car accelerates worse and does not drive as quickly as before;
Strong popping sounds from the muffler. It is impossible not to hear such a sharp and unpleasant sound;
Black smoke from the chimney. When the engine is running, thick black smoke can be seen from the exhaust pipe;
Large carbon deposits on the spark plugs. Can be seen visually.

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. Sometimes this indicator is restored for some time after the car is driven at high speed, but usually the improvement does not last long.

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.

Video: How to use the ELM 327 scanner on a VAZ 2114?

The fuel mixture entering the engine cylinders must have strictly defined proportions of fuel and air content. If their quantity changes in any direction, the result is either a lean mixture, with low fuel content and high air content, or an enriched mixture, in which there is too much fuel.

Incomplete combustion occurs because there is not enough oxygen. Therefore, the residues are released through the exhaust valves and further into the exhaust pipe. As a result, several problems arise at once:

Fuel burns out outside the combustion chamber, which leads to rapid wear of valves and other elements.
The engine consumes too much fuel, but its power only decreases, and it works intermittently, it may not start or stall.

Therefore, a mixture that is too rich is not at all good for the car, just like a mixture that is too lean. Its composition must be strictly controlled, and modern cars have various sensors that help maintain the required proportions in different situations.

In case of various failures, the driver can see warnings on the on-board computer screen.

How to proceed

You will need to check:

First of all, it is necessary to remember whether the on-board electronic system has been reconfigured. It often happens that the problem appears precisely after the ECU has been reflashed.

Here, the power unit usually works normally for some time, but eventually, if the new settings do not correspond to the current ratings of the installed sensors, the problem makes itself known. Ultimately, fuel is supplied to the injector incorrectly.

In addition, there is a possibility of a malfunction in the injection system after the sensor responsible for air flow or some other built into the fuel circuit has been replaced.

In other cases, when the breakdown is not related to the above reasons, you will need to diagnose the power unit using a computer. To do this you will have to go to a car service center.

What does code p0172 mean?

Error p0172 appears just when the mixture is too rich. This is a system error that can occur either accidentally or during real failures. It may appear by chance when the engine has just started, and incorrect data has been received from the sensors several times in a row. When everything returns to normal, this message disappears.

But if this is a real problem, then the driver himself may feel that the car is not behaving as usual - the engine is “choking”, does not hold speed, pulls weakly, malfunctions, and may even stall.

This situation requires immediate intervention - diagnosis and adjustment or repair.

Recommended Tools to Fix P0172

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

Error p0172 means the mixture is too rich (or system too rich). Thus, a re-enriched fuel mixture is supplied to the combustion cylinders. Like the P0171 code, the rich mixture fault is systemic. That is, it does not indicate an obvious malfunction of the sensors, but the fuel quantity parameters exceed the limit value.

OBD II Diagnostic Trouble Code (DTC) P0172.

Possible causes of error p0172

The system that forms the fuel mixture operates based on data from a pair of main sensors:

The lambda probe, located in the exhaust manifold, measures the amount of unburned oxygen. When the mixture contains one part fuel and 14.7 parts air, the sensor returns a value of 1, that is, the composition is optimal. Otherwise, it returns other values, based on which the composition is adjusted. This works like feedback.
The MAP sensor measures the absolute pressure in the intake manifold, helping to calculate the air density in this place and its flow.

In addition, information from other sensors is used - camshaft and crankshaft position, air temperature and throttle position. Different conditions are taken into account, including gaps in different temperature conditions - on a cold and hot engine, in summer or winter conditions. All this allows you to adjust the composition of the mixture.

If any of the sensors transmits an incorrect value, this may indicate either a dangerous situation in a particular unit or a problem with the sensor itself. And this can lead to the appearance of error p0172 - mixture too rich. It can actually be formed due to incorrect initial data.

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:

Eliminating the error: mixture too rich

The fuel mixture consists of just a couple of components - fuel and air. The x proportions are controlled using various sensors. Therefore, the reasons for the over-enriched mixture error may be as follows:

Problems in the systems responsible for air purification and supply.
Malfunctions in systems responsible for fuel supply, for example, fuel pump, regulation system.
A malfunction of any sensor transmitting incorrect information.

The reason may also be a malfunction of the injectors, when even when they are buried they continue to pass fuel into the combustion chamber. Because of this, it appears there in increased concentration.

Identifying these problems takes time. You can start with simple steps, such as checking the air supply. Sometimes you can visually notice that the air filter is dirty, and if it is clogged with dust and oil, it must be replaced. Sometimes this solves the problem.

It is useful to test the sensors and see their readings. A faulty lambda probe can be quickly identified, and it is often the culprit of this problem. The faulty unit can be replaced.

Some car owners independently adjust the injector, making a number of mistakes. As a result, a rich mixture may form, although all components are in good working order. This needs to be fixed as quickly as possible, without waiting for the engine to break down.

The error may appear due to violations of thermal clearances or damage to sealing materials, when there is insufficient compression or the operation of the timing belt is disrupted. This usually requires contacting specialists.

There are also complex problems, for example, those associated with a malfunction of the control unit. It is very difficult to detect and eliminate this on your own; it is better to turn to specialists.

Error P0172 is due to the fact that the mixture is supplied to the cylinders too rich. This is accompanied by the following symptoms:

The engine seems to be choking. When you press the gas pedal, the engine gains speed with a delay, and vibration is felt in the cabin.
Black carbon deposits form on the spark plugs.
Fuel consumption increases because Some of the fuel does not detonate and goes into the exhaust pipe.
The car's dynamics decrease, this is especially noticeable when overtaking and starting from a stop.
Idle speeds float

To solve the problem you need to check:

Mass air flow sensor

First of all, check the mass air flow sensor - MAF. How to check the sensor using a multimeter, read the article at the link.

There is a high probability that the sensor is transmitting incorrect data, which is why a rich mixture is supplied to the cylinders. It is especially important to pay attention to the sensor if there is also a P0102 error.

MAP pressure sensor

The MAP sensor can also be the cause of error P0172. Check the sensor:

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.

Air leak

Check for air leaks after the mass air flow sensor. Leaks often occur due to the receiver's corrugation not being fully tightened. It is recommended to spray soapy water on the parts where air passes through. Places where air passes will become noticeable. If the air leak is eliminated, reset the errors. P0172 should no longer appear.

Fuel injectors

The next thing to check is the fuel injectors. First check if voltage is supplied to each of them. There are special stands for checking injectors, but as a rule, they cannot be found in every city.

Air filter

Check and replace the air filter if necessary.

Throttle valve

Check the throttle sensor. For this

Turn off the engine
Disconnect the wires that go to the throttle position sensor. There will be three wires: power, ground and signal wire.
Start the engine and use a tester to determine the ground and signal wire (exclude the wire in which the voltage is 5 volts to ground - this is power and is not needed now).
Measure the RESISTANCE between ground and signal wire. The resistance should be in the range of 0.8 - 1.2 kOhm.
Then open the throttle fully and measure the resistance again. It should be within 2.3 to 2.7 kOhm.

If the resistance is different, the TPS must be replaced.

Absorber valve

The canister valve is controlled by the ECU. the valve could open and hang in such a position, which creates excess air leaks, which leads to P0172.

The error “Fuel supply system too rich” most often appears in VAZ cars, in particular Kalina, Priora. And also in a number of others: Ford, Opel, Mercedes

Other OBD2 errors

Content

Error p0172 on the VAZ 2114 is a fairly common problem that is signaled by the on-board computer. What does this error code mean, what causes it, and what actions should the car owner take? We’ll talk about this in today’s article.

Error P0172 on the screen

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.

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.

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.

Signs of a rich mixture on a VAZ-2114

A too rich mixture on a VAZ-2114 manifests itself not only by issuing error p072, but also by the following symptoms:

high gas consumption. Moreover, consumption increases sharply and is explained by inefficient consumption of the fuel mixture;

Soot on the spark plug with a rich mixture

loss of engine power. A mixture in which the air content is less than normal burns more slowly than usual, and often not completely. As a result, the piston is not provided with optimal force, which is why the engine power decreases;
black smoke from the exhaust pipe. The reason lies in the lack of filtration of gas from gasoline combustion;

Black smoke with rich mixture

the appearance of strong pops in the muffler. The reason is a lack of air in the engine cylinders.

Lean mixture codes

But you should not think that for all reasons there is only one code, as for all cars. For example, the P0171 code in question is standard. But, in Ford cars, this code will indicate problems in the first cylinder block, while the P0174 code will indicate shortcomings in the second cylinder block. But on some Honda car models, code P0172 (45) may appear, which also indicates a lean mixture error, which turns out to be incorrectly prepared.

On the popular Chevrolet Captiva car in our country, a similar problem will be indicated within its own diagnostic system with code (DTC) P2177. But, the methods for eliminating this code are exactly the same as for other cars. In the Mazda 6, code 2178 may appear, which is exactly the same as what the previously mentioned codes indicate.

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;

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.

Poor fuel assembly: concepts

Lean fuel mixture

- This is a fuel assembly with a reduced gasoline content and an increased air content.

The error code assigned to this error by the on-board computer is P0171. Literally, this code stands for very poor fuel supply. Sometimes poor FA is called low-calorie.

A poor fuel mixture shows itself with the following signs: very poor traction, especially noticeable on steep climbs, engine overheating, the injector makes popping sounds, and white or gray smoke comes out of the exhaust pipe.

Reasons for preparing a lean fuel assembly: fuel pump malfunction, use of gasoline with water or other impurities, fuel sensor malfunction, vacuum hoses or intake manifold malfunction, injectors supply too little gasoline, pressure sensor malfunction.

Signs of a rich mixture

The formation of a rich fuel mixture occurs with a chic set of manifestations.

Problems of preparing car fuel mixture

Ways to eliminate error p0172

If an injection engine prepares a mixture that is too rich, the first thing the car owner needs to do is eliminate various additional settings for the volume of air or gasoline supplied.

If the vehicle has undergone fuel system adjustments, they should be cancelled. If the engine runs for a long time on an over-enriched mixture, the result may be damage to the pistons and spark plugs.

Often a rich mixture on a VAZ 2114 is formed due to incorrect supply of gasoline by the injectors. You should pay attention to the injectors if traces of fuel assembly combustion are found on the outside of the injector. Traces from the combustion of the fuel-air mixture can be found on the copper o-ring. If such signs appear, it is advisable to ensure that the injector is installed correctly.

Cleaning the fuel system of a VAZ 2114

If the problem is in the injectors, then it is not necessary to remove them. To check the functionality, just listen carefully to the noise of the motor in operating condition. Faulty (or clogged) injectors produce a high-frequency, dull sound. Faulty injectors will have to be replaced, but clogged ones can be cleaned at home.

Cleaning injectors

There are several methods for this:

Flushing with special additives that should be added to the fuel tank. The advantage of this method is that the additive not only flushes the injectors, but also normalizes the operation of the entire engine.
Ultrasonic cleaning. This work is not quite simple and requires first removing the injectors from the car and then installing them back. In addition, expensive equipment is needed to carry out such cleaning.
Cleaning the injectors using a syringe and a special washing liquid.

If the cause of error p0172 lies in a dirty air filter, then it is best to simply replace it with a new one. If at the moment there is no money to buy a new filter, then it can be cleaned fairly quickly.

Cleaning the air filter

The procedure is very simple:

open the hood, disconnect the battery and unscrew the screws of the filter safety cover;
manually remove the filter from the grooves of the cover;
treat with a special impregnation, wait 10-15 minutes and rinse the filter element in clean water;
Allow the filter to dry completely and replace it. You can speed up the drying process using a regular home hair dryer.

If the cause of the rich mixture is a faulty pressure regulator, it should be replaced:

disconnect the negative terminal of the wire from the battery;
remove the vacuum hose and unscrew the nuts of the drain tube, holding the hose fitting;
use a rubber ring to connect the washer and tube;
unfasten the clamping bar;
loosen the screws that secure the regulator to the ramp and remove it;
Attach the new regulator in the reverse order.

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 P0172. 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.