High idle engine speeds are possible causes. Why the engine speed does not fall and what to do At idle 1500 and do not fall

Hello dear friends! While operating your car, almost every driver faces certain difficulties and problems. Someone , for others, antifreeze boils, and for others, the engine speed does not drop at all Idling. It is about the latter situation that we will talk with you today.

This is a widespread malfunction in which the engine constantly keeps revs. Leaving the engine at idle (XX), all the same, the tachometer needle does not want to go down.

Similar situations are found in almost everyone who has an injector and carburetor under the hood, diesel and gasoline ICE. At the same time, the reasons for injectors and carburetors are different. Let's take a closer look at them.

How to determine if there is a problem

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

In practice, identifying a problem that has suddenly appeared is quite simple. Even in those situations when a novice is driving, and he does not have much experience in such matters. First of all, you can just listen to operation of the internal combustion engine. The lower the speed of the motor, 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 record exactly what speed 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, for each power unit there are rules for idle speed. Usually it is from 650 to 950 rotations within a minute.

Now take a look at the instruction manual. There, the parameters of the norm for XX are necessarily indicated. If the current values differ 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 helped by on-board electronics. If the revolutions on the twentieth turn out to be higher than the norm laid down by the manufacturer, on dashboard The check engine light will probably come on. Here I advise you to look into our material, where we talked about and their meaning.

Possible consequences

Similar phenomena occur on a large number of machines. Almost any modern and enough old motor able to present such a surprise to its owner. It could be:

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

It would seem that, well, the speed 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 frightening in their cost of restoration.

In no case should you leave an increase in speed at idle.

This can be explained by several main possible consequences.

Here are the potential problems:

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

There are enough reasons to quickly take action and eliminate the provoking factor.

RPM drop on carbureted 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 revolutions are kept at a fairly high level at idle, the reasons may lie in the following:

Idling system incorrectly adjusted. If it has been interfered with recently, be sure to check the current setting;
Problems with . An increase in idle speed may be due to its improper closing. Check the damper for soot. There may also be a chip or crack. There is only a replacement;
Needle valve. The reason is its location. Perhaps when an incorrect dosage of fuel enters the chamber;
Block head gasket. She just burned out. Will 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 performance of the suction. Usually the problem is solved by lubricating the drive and cable.

It is these reasons that most often appear on cars with carbureted engines when at idle the RPMs remain at an abnormally high level. They are potentially considered in situations where the engine almost immediately.

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

Problems on the injector

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

Unlike carburetor internal combustion engines, where all the problems lie in the mechanical part, the injector has a high probability of electronic malfunctions.

Malfunction or failure of the sensor that controls the temperature of the coolant. This is the drive to permanent job in engine warm-up mode. You need a diagnostic scanner and probably a replacement controller;
Malfunction or breakdown of the XX sensor. He is a sensor. mass flow air. Diagnostics with special equipment will help. Eliminate open wiring with a multimeter, replace the assembly as necessary;
The same problems, but with the throttle position sensor. That is throttle valve. The controller either jammed or broke;
Throttle return spring. It can stretch or come off, causing the corresponding behavior of the motor at idle. The node is returned to its place or changed to a new one;
Hall throttle cable. Relevant for older cars. Replacing or lubricating will help solve the problem;
Gaskets for injectors. They don't get damaged that often. Diagnosing the problem is difficult. They are usually checked last.

Be careful when running and observing the behavior of the tachometer in your car. If you see RPMs fluctuating, rising to abnormal levels, and behaving uncharacteristically, don't ignore these symptoms.

Many owners of fuel-injected cars have seen the effects when idle (XX) suddenly drops. Especially often this phenomenon occurs when the engine is warmed up to operating temperatures. Sometimes the RPMs drop so low that the engine stalls. Let's see what can provoke low rpm idling on a warm engine, and also find out why they fall. This information will be useful to everyone.

The origins of unstable engine operation on the twentieth

How will the picture develop if the control unit does not receive data on the amount and volume of air consumed? So, for example, the reaction of the throttle sensor will be as follows - the speed will initially increase, but then the fuel mixture will begin to become poorer, as a result of which low speed will be established on a hot engine. There is only one reason for this - the amount of air consumed by the motor has decreased.

However, the opposite also happens - the fuel mixture is enriched, and the engine starts to gain momentum again. Such cycles can alternate indefinitely, these are floating revolutions. Especially relevant is the problem of low idle on a warm engine in winter.

On some cars, events can develop in a different way - the revolutions grow, for example, up to 2000 rpm, and they remain so. The reason is that the injector injects increased portions of fuel. The amount of air does not grow, otherwise the engine could raise the speed to 3 thousand, however, then it would still start to stall.

Fuel quality

When idle speed drops on a warm engine, you should not discount fuel. It is possible that the problem is not related to the electronics, sensors or executive mechanisms. Maybe the whole point is that the driver fills up with lower-octane gasoline, and the ECU is designed for high-octane brands. Hence the lean mixture, so the control unit has no choice but to work like this.

Possible reasons

So what is causing this problem? One of the most vulnerable links in injection engines are sensors. One of the elements that directly affects the operation of the engine and its quality is the idle speed sensor. Often you can find it near the throttle. This is a stepper motor with a conical shut-off needle. When the throttle is closed, air enters bypassing the damper through the idle channel, which is blocked by a needle.

Another culprit for very low idle is Air is the second important component for cooking fuel mixture after gasoline. Therefore, if the mixture is rather poor, then there is nowhere to take high turns.

When the system malfunctions, the ECU cannot correctly select and calculate the proportions of the fuel mixture in XX mode. As a result, the engine will be unstable, the speed will begin to fall and rise.

A less common cold idle problem with a warm engine can be a malfunction of the EGR system, or rather its valve. The element is installed in the intake manifold and its function is to remove exhaust gases. This is nothing but Periodically the sensor needs to be cleaned.

It will not be superfluous to also make sure that there is no air leakage in the system and check the state of the throttle valve. Often the problem of low speed can be associated with a dirty damper or its mechanical damage, deformation. It often happens that, for one reason or another, the damper jams - hence another reason for low revs.

Why do sensors die?

Experts identify two reasons for low idle speed. One of them is related to the low quality of fuel. Often, an underestimated octane number not only greatly pollutes the working surface of the sensor, but can also cause various malfunctions in the operation of electronic components.

In addition, often the sensors fail due to a banal marriage or exceeding the service life. Inexpensive sensors may well be of poor quality or defective. That's why low idle appears on the car.

How to eliminate air leakage?

In order to exclude or confirm the leakage of excess unaccounted air into the system, check the tightness of the air supply system.

To do this, you can remove the air pipe and blow into it from a compressor or pump. The hose can be placed in water. This will reveal cracks and other defects.

How to check the idle speed sensor?

It is recommended to use a multimeter to check if the sensor is working. The verification procedure is very simple. Replace the resistance between the contacts in the sensor block. It is important that the ignition is on. The resistance between different pairs of contacts should be between 39.5 and 81 ohms. If during measurements the multimeter gives other readings, then the sensor should be replaced.

Checking the DMRV

So, first, to check, turn on the ignition. You need to check the voltage with a multimeter. Measure it between the contacts with the green and yellow wire. On the various cars voltage can vary from 0.9 to 1.2 V. You can determine the output of the mass air flow sensor and appearance candles - black carbon deposits indicate that it is better to replace it.

How to clean the idle speed controller (IAC)?

When there is a problem with low idle on a warm engine, in some cases it can be eliminated by flushing with DXC. To do this, de-energize the car. The regulator is located on the throttle assembly, below the TPS (throttle position sensor). You should prepare a clean rag, a screwdriver, liquid in an aerosol can - this can be any tool for cleaning carburetors or injectors.

Cleaning begins with dismantling - to remove, just unscrew the fixing screws. Sometimes there are bolts. After the sensor has been removed from its seat, you can start the cleaning process. The work is carried out with the help of rags treated with liquid from a can.

It is also necessary to spray from a can on a needle. Last on various models the car can be both metal and plastic. The cleaner will not damage the plastic. But the liquid must not get under the spring. If this still happened, it is recommended to purge the sensor as soon as possible. compressed air. If this is not done, the fluid will wash out the internal lubricant, which will cause complete failure. IAC progress out of service.

Conclusion

As you can see, only a few sensors can provoke low engine speeds at idle. But even one small element can significantly ruin the life of the car owner, especially if the speed does not always fall. But this is not a problem, because this issue can be solved easily, without large investments.

It is necessary that all systems of the power unit work properly. In this case, the engine should work normally both under load and at idle.

In practice, quite often, drivers are faced with a problem when, after releasing the gas, the engine speed does not fall or falls with a long delay. It is quite obvious that high idle indicates a problem and causes 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 on and in cars.

Read in this article

When you release the gas, the speed is increased or “freezes”: common malfunctions

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

However, after the temperature rises, the control unit lowers the idle speed, bringing them back to normal. On many cars with a carburetor, the driver independently increases the speed during warm-up, using the so-called "choke".

At the same time, after the engine is warmed up, normal idling is, on average, 650-950 rpm. If you press the gas and release the accelerator, the speed should increase, and then decrease again to the specified values.

Also, a situation often arises when the speed is slowly dropped or 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 common problems carburetor. Often the engine speed is not reset due to problems with the throttle. For example, when the driver presses on the gas, the throttle must be opened wider to allow more air to enter the cylinders to burn fuel. After the gas pedal is released, the damper closes, the speed decreases.

If the damper does not close completely, an over-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 the carbureted machines the engine speed does not drop often even if the gasket between the carburetor is out of order. Also, the intake manifold, which is damaged, may be the culprit.

The main task is to find the right ratio of fuel and air. Often high levels of fuel in float chamber the carburetor also results in increased RPM. The test should start with the needle valve.

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

As a rule, problems with revolutions can be caused by malfunctions of both mechanical elements and electronic components. In the list of main 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 runs stably and reaches operating temperature faster.

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

Special attention should be paid to gaskets, since air leakage can lead to the fact that mixture formation is disturbed. This means that manifold gaskets, injector seals, etc. need to be inspected separately.

Floating revolutions: reasons

Note that in some cases, the speed does not just slowly fall or stay at the same level, but “float”. In this case, the engine may run unstable. first they fall, then they rise sharply and everything repeats. common cause such a phenomenon is the supply of excess air, which leads to “jumps” in revolutions at the twentieth.

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

If failures occur, the control unit cannot prepare the “correct” mixture for XX mode, which causes speed jumps after releasing the gas pedal or when the engine is idling.

Summing up

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

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

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

If diagnosis is difficult, it is best to deliver the car to a service that specializes in repairing a particular brand of car. As a rule, these are official dealer service stations, less often third-party organizations can be found.

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

The main engine problems with a carburetor power system

The location of the needle valve responsible for adjusting the level of gasoline in the float chamber.
Loose closing of the throttle valve, which often happens when it is clogged or mechanically damaged. A dirty throttle should be cleaned with a special tool that can be purchased at an auto parts store. And in case of mechanical damage to this node, most often, it is required complete replacement carburetor.
Incorrect adjustment of the XX system. This problem often appears after cleaning or replacing the carburetor. To eliminate it, you just need to adjust it, providing the optimal ratio of gasoline and air in the fuel-air mixture.
Consistently high idle may indicate a loose throttle valve located in the primary chamber. This problem appears due to wear of the throttle cable or deformation of the damper itself.
Damage intake manifold or worn gasket between cylinder head or carburetor.

In the case of an injection power system, there are much more possible reasons for an increase in idle speed. This is due to the fact that they can be associated with both the failure of mechanical components and the malfunction of electronic sensors.

The main malfunctions of the injector

Faulty coolant temperature sensor. Interruptions in the operation of this sensor lead to the fact that the motor constantly operates at high speeds, in warm-up mode. In this case, after warming up the power unit to operating temperature the electronic unit control does not reset the speed to normal values, since the sensor signals that the engine has not yet warmed up. The same thing happens when the idle speed controller does not work properly.
Stuck throttle cable. This happens especially often on cars with high mileage.
Violation of the operability of the XX regulator or its electronic sensor, while the idle speed may increase or even disappear.
Throttle position sensor malfunction.
Jumping or excessive stretching of the return spring, which should return the damper to its original position.
Violation of the integrity of the gaskets, rubber seals of the nozzles or the manifold itself. With these malfunctions, excess air from the environment enters the combustion chamber.

The most common reason that the engine speed does not drop to idle when you release the gas may be inaccurate placement of the mat under the accelerator pedal after visiting the car wash.

Summing up

First of all, a malfunction of the injection and carburetor power systems should be diagnosed by inspecting the throttle.

In case of injection engine, to accurately determine the malfunction of a particular sensor will help computer diagnostics. To do this, it is best to use the services of a service that specializes in servicing cars of a particular brand.