Engine speed is lost. Engine speed does not drop at idle: we are looking for the cause and fix it. Why sensors die

02.12.2020

Unstable idle speed or lack thereof is one of the most common engine problems and can be solved in a variety of ways.

Engine

One of the most common problems with a car's engine is erratic or no idle speed. Driving such a car becomes a real problem when driving in heavy city traffic. Besides the fact that the driver can learn a lot of "flattering" about himself from other road users, he can create a real emergency.

The idle system is critical to the operation of the engine, from starting it to the power modes, which is why it is so important to pay attention to it.

The idle system is critical to the overall performance of the engine, from starting to power, and therefore it is so important to pay attention to it. Experienced motorists know what can cause problems with rpm on carburetor and injection engines, and most importantly, how to "treat" these unpleasant automobile "diseases".

Idle system

The early releases had a dependent idle speed, and due to their design, they practically did not cause any problems with idle speed to their owners.

However, the times when a liter of gasoline cost 9 kopecks, and a bottle of mineral water - 10, are over, fuel economy has become relevant. She, in fact, contributed to the emergence of an autonomous idle, introduced mainly to reduce fuel consumption.

The advent of autonomous idling in the design of the carburetor increased the requirements for fuel cleanliness, and also complicated the maintenance of this device. Filters for fuel cleaning began to be introduced into the power supply system, since their absence began to directly affect the stable operation of the engine.

If on early carburetors it was enough to set the idle with a special screw at a certain angle, now everything is more complicated. Idling was separated into a separate system, with its own channels and nozzles responsible for supplying and metering fuel and air. In addition, an idle solenoid valve appeared, which works only when there is power on its winding.

The idle system has become more complicated, which has reduced its reliability, since now any speck or hair in the fuel can lead to interruptions in the operation of the engine or even to its complete stop.

A carburetor equipped with an idle solenoid valve is more economical in fuel consumption, but less reliable in terms of the stability of this idle speed. This is due to the fact that at any time the fuel jet located in the valve can become clogged, and the power supply to the solenoid valve can also be lost.

Unstable turnovers and reasons for their occurrence

Unstable engine rpm can be caused by sticking of the throttle valve, mainly due to its not returning to its original position. Most often, the reason lies in a faulty valve drive mechanics, or in a large amount of deposits on the inner walls of the lower part of the carburetor.

In this case, it is necessary to check the elements of the throttle valve drive and clean the throttle assembly. It is better to check the operation of the drive with an assistant: the assistant needs to smoothly press the gas pedal all the way, and the driver should follow the throttle actuator lever. The flap should take a vertical position and return without jamming to its original position. If the drive of the secondary chamber is mechanical, then at the end of the stroke of the damper of the first chamber, the damper of the secondary chamber should also open, and then also return to its original position.

When the assistant drowns the gas pedal to the end, you need to check the full travel of the throttle actuator lever, trying to squeeze the lever to the extreme position by hand. If the lever has a stroke, then it is necessary to achieve its full stroke from the gas pedal.

When an uneven stroke of the dampers is observed (they close in jerks or do not fully return to their original position), the carburetor must be removed, disassembled and cleaned the throttle body.

If the car is operated mainly within the city, then the shutter of the secondary chamber can generally be jammed, since, in general, traffic in the city is carried out on the first camera. You shouldn't try to use force to develop it. For these purposes, there is a Carburetor Cleaning spray that does an excellent job of doing this.

With this tool, the throttle assembly on the injection motors is also cleaned. In addition, it can be used without disassembling the carburetor: with the air filter removed, inject a small dose of flushing into the primary chamber while adding gas. The motor will "choke", as it were, dropping speed, and will immediately respond with an increase. By repeating this procedure 2-3 times, you can be sure that the throttle assembly is flushed. However, in order to thoroughly "put things in order" in the valve body, it is still better to disassemble the carburetor and rinse it in detail.

Floating speed of the injection engine

Unstable idle speed in most cases is associated with contamination of the throttle assembly or extraneous air suction.

When the throttle assembly is dirty (when visually inspecting oil with dirt), its channels are clogged and the bypass channel is not completely blocked by the idle speed regulator. The throttle assembly is removed and cleaned.

In case of extraneous air leakage, the mass air flow sensor gives incorrect data, which either adds or decreases the amount of fuel in order to equalize the mixture ratio. Turnovers, respectively, then fall, then rise. Leakage is detected by careful examination of the air supply channel.

Quick Start - Solution or Emergency?

An unstable engine start is associated with a malfunction of either the engine itself or its life support systems: the fuel and ignition systems (with a working battery and oil corresponding to the season).

Many people use the Quick Start tool to start the engine, but this is only a temporary solution. It can be used only in an emergency, when the delay is really like death, but at the first opportunity it is necessary to find and eliminate the cause of the unstable launch.

The "Quick Start" tool contains a large amount of highly flammable fractions and promotes quick engine start, which is especially effective at low temperatures.

Use the "Quick Start" tool as follows: without starting the engine, inject the compound into the intake manifold or the primary chamber of the carburetor, and then start the engine. Repeat the procedure if necessary.

Quick Start can also be used to diagnose the power system. When unstable revolutions are observed, interruptions in the operation of the engine, it is necessary to inject the composition into the intake manifold. If the engine is stable, there is a problem in the power supply system. When no changes are observed, either the ignition system or the gas distribution is faulty.

Using ether to start a motor

To start engines, starting fluid is also used - diethyl ether. Ether has high volatility and low flash point (mixed with air in a ratio of 2 to 48%).

However, ether is very insidious; if it is misused (or counterfeit ether), disastrous consequences for the engine are possible literally in the first seconds of launch. This is due to the fact that ether has a high combustion rate, creating enormous shock loads on all elements of the cylinder-piston group. Its combustion is sometimes accompanied by an explosive effect, which leads to instant damage to engine parts.

To prevent this, additional components are introduced into the starting ether liquid, which have lubricating, stabilizing and reducing the combustion rate and the temperature threshold of the mixture's autoignition.

If it happens in winter, it must be borne in mind that the engine must be prepared for winter operation. When the engine is started on summer oil in severe frost, the engine parts may simply "stick" to each other and simply break down after starting. In addition, summer oil will not be able to supply all rubbing vapors after starting, which will greatly increase their wear.

Starting with the use of an ethereal starting aerosol is best done with two people: one turns on the ignition, and the second injects into the intake manifold (moving the corrugation off the throttle) by pressing the spray gun 1-3 times, and only then starts. This will minimize shock loads when starting the motor.

Theoretically, the mixture is allowed to be injected into the cavity of the air filter, but since there have been cases of ignition, it is better to refrain from this method.

A serviceable and fully regulated engine should start independently without using any starting mixtures at temperatures up to - 35 C. Priority should be given to its technical condition, and starting mixtures should be used only as a last resort.

It is essential that all powertrain systems are working properly. In this case, the engine should operate normally both under load and in idle mode.

In practice, drivers often encounter a problem when, after the throttle is released, the engine speed does not fall or falls with a long delay. It is quite obvious that excessive idle speed indicates a problem and is the cause of increased fuel consumption.

In this article, we will talk about why the engine speed does not fall, and also consider the main reasons why such problems arise in cars.

Read in this article

When throttle is released, the RPM is increased or "freezes": common faults

Let's start with the fact that on many cars with an injector, it rises during warming up. This is necessary in order for the power unit to operate stably after a cold start.

However, after the temperature rises, the control unit lowers the speed of XX, bringing them to normal. On many cars with a carburetor, the driver independently increases the speed during warming up, using the so-called "suction".

Moreover, after the engine is warmed up, the idle speed is, on average, 650-950 rpm. If you press the gas and release the accelerator, the revs should increase, and then decrease again to the specified values.

Also, a situation often arises when the speed is slowly dumped or is constantly kept at around 1.5 thousand rpm, 2 thousand revolutions, etc. Naturally, in such cases, the consumption increases and the internal combustion engine wears out more, which indicates the need for diagnostics.

So let's start with the common carburetor problems. Often times, the engine speed will not reset due to throttle problems. For example, when the driver presses on the gas, the throttle must be opened wider to allow more air to enter the cylinders for fuel combustion. After the gas pedal is released, the damper closes, the speed decreases.

If the damper does not close to the end, the re-enriched mixture enters the cylinders, the speed is increased. The cause may be severe contamination of the throttle assembly or damage to the damper itself (deformation). First you need to clean the damper; carburetor cleaning fluid is suitable as a cleaner.

We also note that the damper does not close tightly even when the drive cable is worn out. In this case, the cable must be replaced. On carburetor machines, engine speed does not drop often even if the gasket between the carburetor is out of order. The intake manifold, which is damaged, may also be the culprit.

The main challenge is to find the right ratio of fuel and air. Often, a high level of fuel in the carburetor's float chamber will also lead to increased revs. The test should start with the needle valve.

Now let's move on to the injector. Pay attention to many injection cars. As for the malfunctions, the injection system itself is more complicated, that is, there are more reasons for high rpm compared to the carburetor.

As a rule, speed problems can be caused by malfunctions of both mechanical elements and electronic components. In the list of major malfunctions, experts highlight malfunctions of the coolant temperature sensor, which is installed in.

In simple words, if the specified sensor gives an incorrect signal, the ECU considers that the engine is cold and activates the warm-up mode. In this case, the control unit raises the speed so that the power unit works stably and reaches operating temperature faster.

Also, speed problems can begin due to malfunctions and malfunctions (idle speed controller). It also happens that the throttle cable sticks and wedges. Also, the spring that closes the throttle valve can stretch or be damaged.

Special attention should be paid to gaskets, since air leakage can lead to the violation of mixture formation. This means that it is necessary to separately inspect the manifold gaskets, injector seals, etc.

Floating revs: reasons

Note that in some cases the turnovers do not just slowly fall or stay at the same level, but “float”. In this case, the engine may become unstable. first they fall, then they rise sharply and everything repeats. A frequent reason for this phenomenon is the supply of excess air, which leads to "jumps" in speed at XX.

Such problems arise in the event of a failure of the air supply sensor (), which allows the ECU to calculate how much air has entered and how much fuel to supply to prepare the required mixture.

If malfunctions occur, the control unit cannot prepare the "correct" mixture for the XX mode, which causes jumps in revolutions after releasing the gas pedal or when the engine is idling.

Let's sum up

As you can see, in many cases, in-depth diagnostics may be necessary in order to determine exactly why the engine speed is not dumping. For carburetor engines, cleaning and adjusting the carburetor itself is often necessary, while an injector will.

If the problem does not lie on the surface (the damper cable is acidic, after washing or dry cleaning, the carpet in the cabin is incorrectly placed, which presses the gas pedal, etc.), then it is better to take the car to the service.

The most difficult situation is when it involves a large number of sensors and actuators. In this case, even the use of diagnostic equipment does not always allow you to quickly and accurately determine the problem.

If diagnostics is difficult, it is optimal to deliver the car to a service that specializes in the repair of a specific car brand. As a rule, these are official dealer service stations, less often you can find third-party organizations.

Finally, we note that timely detection of the problem allows you to save other components and assemblies. In other words, high rpms, rpm float and jumps indicate that there is a problem with the air / fuel supply or mixture formation. Ignoring such problems negatively affects the engine and its service life.

How to determine if there is a problem

First you need to understand how you can independently determine the increased or just abnormally high revs on your own car. Indeed, even at idle, there is a certain level of revolutions and it must be stably maintained.

In practice, it is quite easy to identify an abrupt problem. Even in those situations when a beginner is driving, he does not have much experience in such matters. The first step is to simply listen to the work of the internal combustion engine. The lower the engine speed, the quieter it will eventually run. But it's even easier to diagnose the problem with , which is installed on the vast majority of cars and trucks. Look at the position of the arrow and note exactly what rpm you see when driving at a measured, calm pace, and what the device shows after warming up or when you release the gas.

Depending on the engine, each power unit has its own idle speed. Usually this is from 650 to 950 rotations per minute.

Now take a look at the instruction manual. The parameters of the norm for XX are necessarily indicated there. If the current values \u200b\u200bdiffer from the indicators from the manual, this can be considered a deviation. That is, you need to start looking for a provoking factor.

Owners of injection engines are greatly assisted by onboard electronics. If the revolutions at XX turn out to be higher than the manufacturer's standard, the engine check lamp on the dashboard will probably turn on. Here I advise you to look into our material, where we talked about and their meaning.

Possible consequences

Similar phenomena are found on a large number of machines. Almost any modern and fairly old motor is able to present such a surprise to its owner. This could be:

VAZ 2109;
Renault Logan 1.4;
VAZ 2107;
VAZ 2110;
Chevrolet Sens;
Mitsubishi Lancer 9;
Niva Chevrolet;
VAZ 2114;
Kia Cherato;
Chevrolet Lacetti;
Chevrolet Lanos;
Toyota Corolla, etc.

It would seem that the turnover has increased, but nothing terrible is happening.

In fact, processes can occur in the engine that are initially invisible to the driver. But gradually the consequences will become obvious and often daunting in their cost of recovery.

In no case should you leave the increase in idle speed.

This can be attributed to several major possible consequences.

Here we are talking about such potential problems:

Fuel consumption will constantly increase, which will negatively affect your budget;
A hot engine leads to problems with the cooling system and an overall decrease in resource;
Often, the fuel will be corny to fly into the pipe, which also threatens its detonation in the exhaust system;
The total resource of the power unit will begin to decrease;
The knot with which the increase in speed is associated will suffer.

There are many reasons for promptly taking action and eliminating the provoking factor.

The drop in revolutions on carburetor internal combustion engines

Despite the new environmental standards, in our country the number of cars with carburetor engines is quite impressive.

If you notice that on such an engine the rpm is kept at a sufficiently high level at XX, the reasons may lie in the following:

The idle system is incorrectly adjusted. If it has recently been tampered with, be sure to check the current setting;
Problems with ... The increase in idle speed may be due to its incorrect closure. Check the valve for carbon deposits. Chipping or cracking is still possible. There is only a replacement;
Needle valve. The reason is its occurrence. Perhaps, when an incorrect dosage of fuel enters the chamber;
Block head gasket. She is corny burned out. We'll have to change;
The suction is open. To check, you need to evaluate the operation of the damper in the primary chamber. If there is a problem, check the suction function. Usually the problem is solved by lubricating the drive and cable.

It is these reasons that most often manifest themselves on cars with carburetor engines, when idle speed remains at an abnormally high level. They are also potentially considered in situations where the engine almost immediately.

There is another option that is relevant for carburetor and injection internal combustion engines. Here we are talking about a sticking gas pedal.

Injector problems

Separately, it is necessary to consider the situations due to which at XX the revolutions can increase precisely on injection types of engines.

Unlike carburetor ICEs, where the whole problem lies in the mechanical part, the injector has a high probability of having electronic faults.

Malfunction or failure of the sensor that controls the temperature of the coolant. This is a drive for constant operation in the warm-up mode of the internal combustion engine. We need a diagnostic scanner and probably a controller replacement;
Malfunction or breakdown of the XX sensor. He is also a mass air flow sensor. Diagnostics with special equipment will help. Eliminate wire breakage with a multimeter, replace the assembly as necessary;
The same problems, but with the throttle position sensor. That is the throttle valve. The controller is either jammed or broken;
Damper return spring. It can stretch or fall off, causing the engine to behave at idle. The node is returned to its place or replaced with a new one;
Hall throttle cable. Relevant for old cars. Replacement or lubrication will help solve the problem;
Sealing gaskets on injectors. They are damaged less often. It is difficult to diagnose the problem. They usually check it last.

Be careful when launching and observing the behavior of the tachometer in your car. If you see RPM float, rise to abnormal levels and behave abnormally, do not ignore these symptoms.