"Poor mix" - what is it? Causes of formation, consequences

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:41

In order for the car to work well, the engine needs quality power. In order for an explosion of the required power to be obtained in the combustion chambers, the mixture of fuel and air must be of high quality. Sometimes it is prepared with deviations in one direction or the other. This is a poor mixture, or vice versa - a rich one. What is it, what are the causes of lean fuel mixture, symptoms and how does the engine work? Let's try to answer these questions.

The process of mixture formation in car engines

In an internal combustion engine, a combustible mixture of the required composition is prepared in carburetors or, in the case of an injection power system, is calculated by electronics. A mixture where 15 kg of air is used for 1 kg of gasoline or other fuel is considered normal. In this mode, the engine runs quite economically, while its power is at a high level. To save money, the amount of air in the mixture is increased. So, a lean mixture is when 1l of gasoline is used up to 15-17 kg of air. Fuel consumption becomes minimal, and power losses are only 8-10%. A lean mixture is when more than 17 kg of air falls on 1 liter of gasoline. On such a composition, the engine is unstable, a large amount of fuel is consumed, and power is reduced. This is harmful to the power unit. In addition, this phenomenon often leads to misfiring in the ignition system, delays when pressing the accelerator pedal.

Also, the motor may change the sound of operation and become unstable. In injection units that comply with Euro2, a lambda probe is installed. It controls the quality of the fuel mixture supplied to the combustion chambers.

Why does the mixture get lean

Owners of injected cars know that with the help of the ECU and the corresponding settings in the firmware, the power unit can independently change the ratio of air and gasoline vapors, that is, change the fuel mixture. Many people think: the motor works automatically, and that's good. However, most owners of injection cars forget about balance. Sometimes a lean mixture is prepared. Why does this happen? There are various reasons for this.

Main signs of lean fuel mixture

The main symptom that determines that the car is running on the wrong composition is an engine that constantly stalls. With a very small amount of gasoline vapor in the mixture, the spark generated by the candle simply cannot ignite such fuel. Another sign is that the car twitches in the process of movement, or even moves at all.jerkily. Sometimes these symptoms can also indicate other malfunctions. Therefore, it is worth checking other systems as well.

You can tell if a lean air-fuel mixture is being prepared by looking at the candles. But this is true only for injection units. If they are brown, the engine is in perfect order. If the candles are white or light, then there is a lot of air in the fuel composition. If a dark soot is found on the element, this indicates a lack of air. However, carbon deposits are not always a good indicator of a wrong mixture. In the event of an incorrect ignition timing, the color of the candle does not correspond to the normal one. If a lean mixture is supplied to the engine, the car owner will hear characteristic pops in the muffler. When it's just a lean mixture, it will shoot like a machine gun. If, on the contrary, the fuel composition is too rich, then the explosions will be single and short. And finally, the most accurate sign and diagnostic method is to check exhaust gases using a gas analyzer. If the engine is running in the wrong mode, the on-board computer or diagnostic system will also report this. In the list of errors of modern ECUs there is an error - a poor mixture. It is designated P0171.

Effects of running a lean engine

In general, the consequences are not so many. The engine will choke when idling. There is also a serious risk of overheating - the fuel mixture burns much more slowly than necessary. It will be difficult for the engine to rev under load. In the most serious situations,when a lean mixture is fed for a long time, the engine overheats greatly, which in most cases leads to burnout of the valves. And these are serious repair costs.

Also among the consequences is a huge fuel consumption. It increases due to difficulties in the process of gaining momentum. Therefore, owners of cars with such problems are advised to drive in low gears.

Reasons for lean mix

There are several typical reasons why the fuel mixture is not properly prepared. All these reasons can be divided into a large amount of air and a small amount of fuel.

Lean mixture errors can often occur with high air supply. In this case, it is recommended to check the fuel flow sensor - very often the sensor channels become dirty. The second reason is a vacuum leak. The third is the EGR valve, which sucks in extra air. The valve may be broken or not close properly. If a lean mixture enters the cylinders, the reasons are the injector, ignition, fuel system, malfunction of the gas distribution system.

How to check the EGR valve

To check the operation of this valve, it is first dismantled and then checked. The test can be carried out with compressed air. Air is supplied to one of the holes - the valve must work. You can see it at the top through the hole. The valve becomes clogged due to the presence of dirty air in it. On a socket or plateelement formed carbonaceous deposits. The valve sticks, and as a result, an incorrect, and often too lean mixture is prepared.

DMRV sensor

Sometimes you need to check everything you can. It is worth starting with the diagnosis of sensors. As you know, one of the most popular problems is a clogged or clogged air flow sensor. If a large amount of dirt has accumulated on it, then this often leads to a slow response of the computer to the air flow and its change. Additionally, the sensor may become contaminated with fuel vapors that pass through the intake manifold. Also, plaque can build up through the throttle body when the engine is not running. A layer of paraffin is deposited on the sensor, due to which incorrect data on the proportions of the fuel mixture enter the ECU.

Then a situation arises when the engine control unit cannot add the required amount of fuel to the mixture (while the amount of air is already large enough). And then an error appears on the sensor display - a lean fuel mixture.

Faults in the intake system

Throttle Diagnosis is also recommended to troubleshoot a lean mixture problem. The position of the damper must clearly correspond to the position of the accelerator pedal. If the throttle valve is automatic, it is important to pay attention to the fact that its position corresponds to the temperature of the power unit. On a hot engine, it should be fully open, on a cold one, it should be turned to a certain angle. If the damper is open, thenair damper control system defective. What else is sinned if a lean mixture forms in the engine? The reasons are the injector and damaged intake manifold gaskets. To eliminate this malfunction, it is recommended to tighten the manifold, and, if necessary, replace the gaskets.

Timing problems

So that the gas distribution mechanism does not affect the leanness of the fuel mixture, it must be checked. And if necessary, adjust. When examining the gas distribution mechanism, special attention is paid to the tension roller and the belt (its condition and marks). If the drive is chain, then the chain is checked along with the tensioner system.

Fuel system

Checking the fuel system will not be superfluous. Here it is important to check the performance of the injectors, but this can only be done with special equipment. Often, most injector problems are associated with low-quality gasoline - then you can get off with a simple flush of these parts.

Then check the fuel pressure level and the performance of the fuel pump, if there is one in the system. Check the voltage at the pump. Among other things, they check the fuel pressure regulator and the fuel filter.

False errors

It happens that the system, along with lean mixture errors, issues other codes. For example p0100 or p0102. They immediately show that the cause is in the sensor. To solve the problem, you need to clean the sensor. For these purposes, it is recommended to use special tools forcleaning electrical appliances. But a replacement is better.

Lean mixture codes

Don't think that if a "lean mixture" error occurs, the reasons for this report only one code. For example, P0171 is standard, but for Ford cars, this code reports problems in the first cylinder. Some Honda models may have a P0172 code that reports a lean condition.

On the popular Chevrolet Captiva, the mixture problem is indicated differently - P2177. But to eliminate it, you need to use universal methods. On a Japanese Mazda-6, code 2178 appears, which also indicates a lean mixture. All this is determined by the method of computer diagnostics.

Repair ASAP

It should be remembered that if the engine has been operated for a long time with such problems, this can significantly reduce its resource. A lean mixture can cause premature failure of a huge number of various components and assemblies. In this case, the repair will be much more expensive than if the diagnosis is made in time and the malfunction is eliminated.