Lean fuel-air mixture: injector, carburetor, LPG

When P0171 appears, it indicates that the engine is receiving too little fuel or too much air. This causes the air/fuel mixture to form incorrectly, leading to problems.

For proper operation of the power unit, an optimal mixture is necessary. The standard fuel to air ratio is 1:14.7. If there is a significant deviation from this indicator, the mixture becomes rich (too much fuel) or lean (too much air). It is a too lean mixture that causes error P0171 to appear.

Symptoms of malfunction

Engine operation with a mixture that is too lean is manifested by the following symptoms:

• significant loss of power;
• The Check Engine light is on on the instrument panel;
• engine throbbing or throbbing (unstable idling);
• problems starting the engine;
• motor overheating.

If the problem with a lean mixture is not addressed, fuel consumption increases, as the driver is forced to press harder on the gas and drive at higher speeds. Damage to the catalytic converter can also occur over time.

Dips when pressing the gas - we diagnose and fix the problem

Cars are complex mechanisms with very interesting operating systems. Every time a certain malfunction or problem is detected, the car owner strives to understand its nature, and, if possible, eliminate it himself. If your car begins to experience dips when you press the gas, you should contact a specialist, but before that you can check several of the most common options for the presence of this unpleasant manifestation.

The reasons for this phenomenon may lie in various factors. For carburetor cars, for example, this may even be a physical malfunction and sudden movement of the throttle valve. But often we are talking about the breakdown of certain functions of the electronic control of the fuel supply system. Let's take a closer look at all the intricacies of this breakdown.

Type of failures when pressing the gas - determine the cause of the malfunction

Before drawing any conclusions about the problem, it is worth determining the type of failure, which will often tell you the node in which you need to look for a breakdown. The most common option for carburetor engines is a second lack of traction, and then a sharp jerk. The carburetor itself is often to blame for this, but spark plugs can also be to blame for this phenomenon.

Considering the fairly simple work with candles and wires, this theory is worth checking first. Such failures due to the fault of spark plugs or wires can happen on injection and even diesel power units. The following components may also be responsible for the presence of such problems in a car:

• fuel distribution system - the jets can get clogged, which causes jerking when you sharply press the gas pedal;
• damage directly to the carburetor or injector system;
• inconsistencies in the operation of the electronic fuel control system;
• breakdown of engine temperature and gasoline mixture enrichment sensors;
• problems with the car's electronic system, computer malfunctions.

The last breakdown is the most common manifestation that determines the negative aspects of transport operation. Today, a breakdown or failure of the on-board computer to function correctly makes the vehicle impossible to operate. This is the main disadvantage of high technologies that are so eager to be introduced into modern technology.

But failures when pressing the accelerator pedal are not always the result of a failure of the computer or sensors. The most common cause of the problem is broken spark plugs. But if, after replacing the spark plugs, the problem repeats after several hundred kilometers, you should look for the problem in the sensors that affect the enrichment of the mixture. Due to their incorrect operation, spark plugs quickly fail.

Non-standard cases and reasons for failures when pressing the gas pedal

Often, with this problem, drivers turn to specialized service centers, because communication with the specialists of such companies can often tell you non-standard reasons for failures in engine operation. Sometimes, when diagnosing a car, specialists find uneven engine operation, which, combined with failures during acceleration, means a breakdown of the main idle speed and fuel economy sensors.

Sometimes failures occur due to a lack of fuel, but it often happens that gasoline flows like a river without any obstacles, which also prevents it from igniting properly. In such situations, the car may stall and show incredible fuel consumption figures. The only way to deal with such problems is as follows:

• bringing the car to a specialized service with high-quality computer diagnostics;
• performing a thorough check of the operation of each component of the machine, especially the fuel supply system;
• preventive cleaning of the injector, jets or injectors depending on the engine type;
• checking the correct operation of the engine control computer program;
• replacing spark plugs, replacing fuel filters and other elements that require updating.

A huge range of problems can cause such problems. Therefore, you should not concentrate only on the fuel supply system or only on the spark plugs. It is necessary to comprehensively diagnose the car, find all possible problems and eliminate them. Of course, you can do this yourself only if you have a sufficient number of skills and tools.

By turning to specialists, you get access to the extensive experience of professionals. If you are faced with a certain problem, then other owners of cars of your make and model have also faced this problem more than once. Therefore, with the help of the experience of an official service center, solving the problem will be much easier.

See more information about possible causes of engine failure in the video:

Let's sum it up

If you are faced with a problem such as dips when pressing the gas pedal, go to a car store and buy new spark plugs. This often helps get rid of the problem or temporarily delay a trip to the service center. If the problem recurs again, you should go to specialists and conduct a full diagnosis of the computer control and fuel supply system.

After such a study, you can easily obtain the necessary information about the problem and make a decision to repair or replace certain machine components. Often, repairing such a problem is not too expensive. Have you ever had problems with symptoms such as engine failure?

Causes of DTC P0171

Since the mixture can be lean due to too much air or not enough fuel, we will look at these two problems separately.

Reasons for the increase in air quantity:

• Vacuum leak (air leak) through lines, intake manifold gaskets, throttle valve, mass air flow sensor, EGR valve, idle air control, vacuum brake booster, etc.;
• malfunction of the mass air flow sensor (MAF);
• oxygen sensor malfunction.

Fuel shortage can be caused by the following factors:

• decreased fuel pump performance;
• dirty fuel pump screen;
• clogged fuel filter and injectors;
• Fuel pressure regulator malfunction.

Where to begin

You should start setting up the Solex 21083 carburetor by adjusting the fuel level in the float chamber. This involves directly starting the engine and warming it up for five minutes. Then the motor is turned off and the following steps are performed:

1. The fuel supply hose is carefully separated to prevent gasoline from entering the chamber during further operation.
2. The five screws securing the cover are removed.
3. The choke system cable is removed.
4. The lid is lifted horizontally with extreme caution so that the floats are not damaged.
5. In the chamber itself, the fuel level is measured using a ruler or caliper.

The distance from the top level of gasoline to the edge of the sealing surface of the lid should be from twenty-three to twenty-five millimeters. It is necessary to select an average value, since the fuel level is not able to be in a constant state due to the manifold, which itself does not have the ability to be in a horizontal position all the time. If there is a deviation from the norm in the parameters set earlier, then it is enough to bend the float holders to correct the situation.

The main reasons for the lean mixture in the injection system

The reasons for a poor mixture on the injector are clogged filters and injectors, air leaks, and wear of the fuel pump. The pressure control regulator in the mechanical injection system may also become clogged. Thus, the back pressure on the dosing plunger increases, which leads to clogging of the strainer and dosing channels. All this can lead to failure of the electronic-mechanical injection system.

If the throughput of the injector decreases even by 10%, this can already lead to breakdown of the oxygen sensor. A clogged injector can also result in resonating detonations, which can significantly damage the engine itself.

You can improve engine parameters (power, efficiency) by cleaning the injector. It is recommended to clean the injector every 20,000 - 30,000 km. Adhering to this cleaning interval will allow you to maintain the injector in proper condition.

It is also necessary to look at the condition of the throttle, since fuel vapors that come from the intake manifold tend to settle on the surface of the throttle valve and other parts associated with it. This leads to changes in the parameters of the air-fuel mixture. Contamination of this area of ​​the engine is very difficult to detect. You can clean the throttle valve using an aerosol spray.

The injector can be cleaned in the engine itself or completely removed and cleaned using a special mechanism.

When cleaning the injector inside the engine, a compressor is needed to direct the atomizer into the fuel system, allowing the valves and combustion chamber to be cleaned. The cleaning procedure takes 10 – 15 minutes. If this procedure does not bring the desired effect, it is recommended to remove the injector. This event is not very cheap and requires dismantling the injector and the use of expensive equipment (ultrasonic treatment, washing with detergents in different directions).

A lean fuel mixture is also associated with excess air. Main reasons:

• — presence of dirt in the air flow sensor.
• - vacuum leak.
• — air entering the intake manifold due to the EGR valve not closing tightly.
• — EGR pressure sensor malfunction.

To eliminate the above problems you need to:

• — check the tightness of the collectors and all hoses.
• — check the functionality of the oxygen flow sensor (lambda probe) and air flow sensor (MAF).

The most common cause of a “lean mixture” error is a clogged air flow sensor. The sensor's response to changes in air flow parameters may be slowed down due to the presence of a large amount of dirt on its wire. The fuel flow sensor can also become clogged with fuel vapors that escape through the intake manifold and throttle body when the engine is not running. Thus, these vapors accumulate in a paraffin layer on the sensor wire, which causes a signal to be sent about a lack of air. If the MAF sensor malfunctions, it must either be cleaned with a special product for electrical appliances or simply replaced.

What is a lean and rich mixture?

Welcome! What is a rich mixture, please tell me if it’s not difficult for you? What is the poor thing then? We are asked such questions mainly by young guys, the older generation is not interested in this and therefore many people have to explain everything in detail what and how, so in order not to explain any more, we wrote this article in which we answered these two questions in as much detail as possible, but However, if you have any other questions, then ask us them in the comments and we will answer them too!

Note! At the very end of the article, there is a very interesting video about how using a lean mixture you can save fuel in a car, but before you start watching it, read the entire article so that you understand at least a little what a lean mixture is and what it is rich mixture!

Basics! Have you heard anything about the engine power system? If you just blow about it, then a picture of a battery appears before your eyes, a picture of some wires emerges, but in fact, power is not related to the battery and not to the wires, the whole point is that for the engine to work, it needs to be powered by something, you already know that the car drives only because an explosion occurs in the cylinder, that is, in the car there are four cylinders, in each of them an explosion occurs at a certain time, namely, the mixture of gasoline and air is first compressed (Number 1), and through strong compression, the spark plug gives a spark and the mixture of gasoline and air ignites, thereby after this ignition an explosion occurs (Number 2) during which the piston flies down and, by inertia, reaches its dead center again, where after this an explosion occurs again and the same thing repeats situation until you turn off the car's engine.

Now let's get closer to the power system, for this you just need to understand what parts belong to this system and you will understand in the future when we talk about the power system, so this system includes all those parts that supply fuel and all those that supply air to the cylinder, for example, on injection cars, the power system looks like this:

And if we take carburetor cars, then their power system also consists of parts that relate to the fuel supply and parts that relate to the supply of air to the cylinders, for example, see the diagram of the VAZ 2109 car:

What is a rich mixture?

Any type of mixture involves a mixture of fuel and an air mixture, this combination is usually 1 to 14, or 1 to 12, etc. In fact, this means this, namely 1 kilogram of gasoline per 14 kilograms of air and the same with the second value, namely 1 kilogram of gasoline per 12 kg of air, etc.

This is the so-called mixture, the most normal mixture level is somewhere around 1 to 14, at this level the car will drive decently and will not consume much fuel either, but if you want to enrich this mixture, that is, make less air and more gasoline, then you can enrich it to 1 to 12, with this combination of gasoline will be spent more than with the previous combination, and this is understandable because 1 kg of fuel already accounts for less kg of air, so fuel will be spent faster, but the car will drive better than with the previous mixture.

But you can’t make the mixture very rich, for example, you can’t make 1 kg of fuel to 5 kg of air, because if the mixture is so rich, then your engine will stop running normally, and most importantly, the engine will heat up very quickly and appear to no one unnecessary detonation, which has a very detrimental effect on the engine and reduces its life by a very decent number of times, so as you already understood from this, you cannot greatly richen the mixture, about 1 in 12, or 1 in 13 will be enough. (You can see what detonation is and why it has such a detrimental effect on the engine in the article entitled: “What is engine detonation?”)

Now a few more words about a highly enriched mixture, have you ever noticed black smoke from the muffler of any car? Basically, such smoke occurs precisely because of an over-enriched mixture in the car, so if today you adjusted the carburetor yourself or gave it to someone else, and after adjustment, black smoke began to pour out of your chimney, then this indicates that the carburetor was configured incorrectly and thus the mixture was very much over-enriched, after which the car should start to drive worse, fuel consumption should also increase and, accordingly, this very black smoke will begin to pour out of the car’s exhaust pipe.

Note! By the way, the same situation will happen with the injector as with the carburetor, the situation which is described a little higher, if a car with distributed fuel injection (Injector) is given into the hands of a not very experienced tuner, and he, as they say, will incorrectly wire the brains, thereby causing the pipe to also begin to emit black smoke and this will indicate that the mixture is over-enriched, and thus, as has already been said, fuel consumption will increase, the car will drive worse, detonation will appear and much more, so let experienced people do the brainwashing on your car and Don’t let just anyone set up carburetors either!

And in conclusion, we note a couple of facts due to which the mixture itself can become rich, without interfering with the carburetor, for example, one of such factors is a heavily contaminated air filter, because when it is contaminated, little air begins to enter the cylinders and so much gasoline will be supplied and therefore the mixture itself will become richer, which will subsequently lead to a reduced engine life. (This applies only to the carburetor, because in the injector the brains themselves distribute how much fuel needs to be supplied to the engine, for example, you set it to 1 to 14 and the injector will always supply that much to the cylinders)

What is a lean mixture?

Note! Before you start reading about the lean mixture, be sure to read about the rich one, because everything the main thing has been said and chewed on, so you may not understand something here!

We are talking too much about the rich mixture, we also need to tell you about the poor one what’s what, in general, as you already understand, the normal mixture is about 1 to 14 liters, but this can be enriched to a maximum of 1 to 12, the car will really run better, but unfortunately the consumption will also become higher, but this mixture can also be leaned to a maximum of about 1 in 16, with such a lean mixture the engine will consume less fuel, but unfortunately the ride will be worse, all these values ​​​​where the maximum is written indeed, they will have practically no effect on the engine, that is, its resource will not decrease and will not increase at the same time, but if you go beyond these limits, then the service life and driving performance no longer begin to suffer much and thus the engine drives poorly and wears out faster .

Idle mode - second stage

Having completed adjusting the fuel level in the float chambers, the engine again warms up, coming into working condition. Further work proceeds as follows:

1. The mixture quality screw is located in the recess of the lower part of the carburetor, and then screwed in counterclockwise all the way.
2. When tightening this part, it is very important to control your own strength, since excessive persistence can lead to thread failure.
3. Make five or six turns clockwise to remove the screw.
4. The engine starts again and the choke is removed.
5. The quantity screw allows you to set the minimum frequency for the motor to operate without interference.
6. If the device is working properly, then the revolutions are made in an amount from five hundred per minute to one thousand two hundred.
7. The quality screw is turned at a fairly slow pace until unstable motor operation begins.
8. Then, in one or one and a half turns, it turns back again for stable frequency activity.
9. The idle speed is regulated by a quantity screw ranging from eight hundred and fifty to nine hundred pieces per minute; if it is not possible to establish the process, then the quality screw comes to the rescue.

• Attention!

The result of adjusting the idle speed is a competent ratio, where the engine operates extremely steadily and with a minimum vacuum.

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.

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