Many owners injection cars could observe the effects when Idling(XX) suddenly the speed drops. This phenomenon occurs especially often when the engine is warmed up to operating temperatures. Sometimes the revs drop so low that the engine stalls. Let's figure out what can provoke low revs 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 at XX

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

However, the opposite happens - the fuel mixture becomes richer, and the engine begins to gain speed again. Such cycles can alternate endlessly; these are floating revolutions. The problem of low idle speed on a warm engine in winter is especially pressing.

On some cars, events may develop differently - the speed increases, for example, to 2000 rpm, and remains there. The reason is that the injector injects increased amounts of fuel. The amount of air does not increase, otherwise the engine would be able to increase the speed to 3 thousand, however, then it would still start to stall.

Fuel quality

When the idle speed drops on a warm engine, you should not discount fuel. It is possible that the problem is not related to electronics, sensors or actuators. Maybe the whole point is that the driver fills 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 causes this problem? Some of the most vulnerable links in injection engines are sensors. One of the elements that directly affects engine performance and quality is the idle speed sensor. You can often find it near the throttle valve. This stepper motor with a conical locking needle. When the throttle is closed, air bypasses the damper through the idle channel, which is blocked by the needle.

Another culprit for very low idle speed is Air - the second important component for cooking fuel mixture after gasoline. Therefore, if the mixture is lean enough, then high revs nowhere to come from.

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

A less common problem of low idle speed on a warm engine can be incorrect operation EGR systems, or rather its valve. The element is installed in the intake manifold and its function is to remove exhaust gases. This is nothing more than Periodically the sensor needs to be cleaned.

It would also be a good idea to make sure that there is no air leak in the system and check the condition of the throttle valve. Often the problem of low speeds can be associated with a dirty valve or its mechanical damage or deformation. It often happens that for one reason or another the valve jams - hence another reason for low speeds.

Why do sensors die?

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

In addition, sensors often fail due to banal defects or exceeding their service life. Inexpensive sensors may well turn out to be of low quality or defective. This is why low idle speeds appear on cars.

How to prevent air leaks?

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?

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

Checking the mass air flow sensor

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 wires. On various cars the voltage can vary from 0.9 to 1.2 V. The sensor output can be determined mass flow air out of order and appearance spark plugs - black carbon deposits indicate that it is better to replace them.

How to clean the idle air control (IAC)?

When there is a problem with low idle speed on a warm engine, in some cases it can be eliminated by flushing the IAC. To do this, de-energize the car. The regulator is located on 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 product for cleaning carburetors or injectors.

Cleaning begins with dismantling - to remove it, just unscrew the mounting screws. Sometimes there are also bolts. After the sensor was removed from its seat, you can begin the cleaning process. The work is carried out using rags treated with liquid from a spray can.

It is also necessary to spray the needle from the can. Latest on various models a car can be either metal or plastic. The cleaner will not damage the plastic. But the liquid should not get under the spring. If this does happen, it is recommended to blow out the sensor as quickly as possible. compressed air. If this is not done, the liquid will wash away internal lubrication what will cause full exit IAC is out of order.

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 drop. But this is not a problem, because this issue can be solved easily, without large investments.

Owners of front-wheel drive VAZs have enough troubles throughout the entire operation of the car. One of the most annoying ones is high revs idling, moreover, on an already warmed-up car. This problem usually causes annoyance because there are too many reasons for its occurrence, and finding them is not easy.

Let's list them.

1. The most basic is a malfunction or failure of the mass air flow sensor.
2. No less common is the breakdown of the idle air control valve.
3. A crankshaft position sensor providing incorrect information to the control unit can also be the root of high or floating idle speed.
4. The throttle position sensor may also be to blame.
5. It happens that for some reason the gas pedal does not return all the way back. Moreover, this happens both because of a banal malfunction of the cable, and because of something completely ridiculous - for example, after washing the car, they covered the driver’s mat in such a way that the tip of the mat began to touch the pedal.
6. Heavily clogged air filter. Because of this, the combustion mixture is too rich in gasoline, again resulting in high idle speeds.
7. The cable came off the throttle valve.
8. Engine temperature sensor faulty. It gives the car’s “brains” incorrect values, which increase the crankshaft speed, thinking that the engine is cold.

As you can see, in front of us is a whole forest of the most various reasons why there are high revs! Next, we will take a closer look at the most typical, plus the most common problems associated with the problem described. At the same time, we’ll figure out how to eliminate them with our own hands.

Ways to eliminate the “sore”

If such a problem occurs, you need to look for which node is to blame analytically, checking all the specified sensors.

First, consider the following fix option problematic situation. Let's assume that a VAZ 2110 has high revs. An examination of the suspected components for faulty components showed that the throttle position sensor has traces of rust. It is located directly above the throttle valve. Measurements with a voltmeter showed that when the engine is idling, the voltage on it remains high - which means it does not close the damper.

How to fix the problem? For this we only need a screwdriver. Let's begin the procedure.

1. By disconnecting the terminal block and also unscrewing two screws, we dismantle the assembly.
2. We notice that traces of rust inside interfere with the movement of the wheel that regulates the position of the damper.
3. We fill the insides of the defective device with a penetrating anti-rust aerosol.
4. Use a development screwdriver to turn the wheel.
5. We reassemble in reverse order.

Check to see if the engine idle speed is now high. The problem should go away.

Now let's look at another case. Let's say we have high idle speed in a VAZ 2114. This is what we do when faced with this situation.

When clarifying the circumstances of the problem under investigation, we always initially check the operation of the idle speed sensor. This device consists of a needle embedded inside an electromagnetic coil. The needle either moves inside the coil, moving away from the hole in the throttle pipe, or moves out, closing this hole, thereby stopping the supply of air for combustion of the mixture.

Also read about and.

This element is located at the throttle valve, opposite the gas pedal cable. To diagnose it, we pull out the terminal block from it, start the car, after which we see that we still have high engine speeds that have not changed at idle. Then we remove this defective unit, then clean it or replace it. For work we take:

• screwdriver;
• toothbrush;
• petrol.

Begin.

1. Unscrew the two screws. We take out the broken node.
2. We connect the wiring to it. Turn on the ignition. If the needle of the device moves slightly inside the coil to the touch, then it is working.
3. If the needle does not respond when feeding electric current, wash the device using a toothbrush with gasoline.
4. We do the assembly in reverse order.

When you cannot restore the functionality of this unit with your own hands, it is better to purchase a new one. Moreover, the cost of spare parts is low.

Other fixes

Of course, the options considered are not exhaustive possible ways correction of the shortcoming when high speeds are noticed precisely on a warm engine. To further study the most common situations, let's look at the case of a malfunctioning mass air flow sensor.


This device is responsible for supplying the correct portions of air for combustion of the mixture, and also provides data to the unit electronic control about these portions so that the unit proportions the supplied portions of gasoline.

This node can be diagnosed as follows. It is necessary to disconnect the terminal block from our mass flow regulator, and then start the engine, after which you need to drive at rpm crankshaft above 2000 rpm.

This will automatically launch emergency mode, portions of the mixture are now calculated only by the position of the damper. If the sensations show that the car with the disconnected sensor has become more dynamic than with the connected one, then the malfunction of this unit is obvious.

To replace it, take the following tools:

• Phillips screwdriver;
• flat screwdriver.

We are starting renovations.

1. After turning off the engine, disconnect the wires from the mass air flow sensor.
2. Loosen the clamp and remove the hose on the inlet pipe.
3. We dismantle the defective device by unscrewing two bolts.
4. We are replacing the device.
5. We do the assembly, moving backwards point by point.

This is how it gets eliminated this reason high speed.

For some reason it didn't help

Now let's look at another situation. The car owner changed, for example, the idle speed sensor, and the crankshaft speed became high, or remained high as before.

The reasons for this unpleasant phenomenon may be as follows.

1. Most likely, the car enthusiast made the replacement just like that, at random, maybe it would stop turning too quickly. The real state of affairs suggests that the fault needs to be looked for elsewhere.
2. If this sensor is not a completely new model, it has adjusting bolt, it may be necessary to tighten it to adjust the problem unit. Modern valves idle speed when installing them do not require any additional adjustment. However, for example, if a Priora has high idle speeds, then of this car You can look for the adjusting screw.
3. It is possible that new spare part turned out to be defective.
4. The new spare part was installed incorrectly.

Here, perhaps, all the roots of the phenomenon are listed.

Let's talk about cost

Not everyone can afford this type of repair, such as even reinstalling a sensor. Although the main difficulties are caused not so much by replacing one of the sensors involved in the process, but by diagnosing the sources of overestimation of the crankshaft speed when idling. After all, we have found that the search for the causes of this disease is complicated by their diversity.

If a car enthusiast decides to contact a service station with a request to find the cause of high engine speeds at idle, then the cost of diagnostics will be according to major cities The Russian Federation will be like this.

City	Price
Moscow	700 rub.
St. Petersburg	650 rub.
Ekaterinburg	500 rub.
Samara	500 rub.
Krasnodar	550 rub.

Since the cost of manipulation is low, if a car owner doubts the success of a manual diagnosis, he can safely contact a service station.

Throughout the article, we looked at the main options for solving a common problem. Now, if a car enthusiast encounters an increase in idle crankshaft speed, he will already know what to do.

Now read about and.

Hello, dear friends! When operating their car, almost every driver faces certain difficulties and problems. Someone , for others, antifreeze is boiling, and for others, the engine speed does not drop at idle. It is the latter situation that we will talk about today.

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

Similar situations occur in almost everyone who has an injector and carburetor under the hood, diesel and gasoline internal combustion engine. However, 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 speeds at own car. After all, even at idle there is a certain level of speed and it must be stably maintained.

In practice, identifying a problem that suddenly appears is quite simple. Even in situations where a novice is driving, and he does not have much experience in such matters. The first thing you can do is just listen to internal combustion engine operation. The lower the engine speed, the quieter it will ultimately operate. But it's even easier to diagnose the problem using , which is installed on the vast majority of passenger cars and trucks. Look at the position of the arrow and record exactly what revolutions you see when driving at a measured, calm pace, and what the device shows after warming up or when releasing the gas.

Depending on the engine, for each power unit There are different idle speed limits. Usually this is from 650 to 950 rotations per minute.

Now take a look at the instruction manual. The normal parameters for XX must be indicated there. If the current values ​​differ from the values ​​​​from the manual, this can be considered a deviation. That is, you need to start searching for the provoking factor.

Owners of injection engines are greatly helped by on-board electronics. If the speed at idle turns out to be higher than the norm set by the manufacturer, at dashboard The check engine light will probably come on. Here I advise you to take a look at our material, where we talked about and their meaning.

Possible consequences

Similar phenomena occur on a large number of machines. Almost any modern and sufficient old motor is capable of presenting such a surprise to its owner. It 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 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 recovery.

Under no circumstances should you allow the revs to increase while idling.

This can be explained by several main possible consequences.

Here we're talking about about these 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 reduction in service life;
• Often fuel will simply fly away into the pipe, which also threatens its detonation in the exhaust system;
• The total resource of the power unit will begin to decrease;
• The node associated with the increase in speed will suffer.

There are quite a lot of reasons for promptly taking action and eliminating the provoking factor.

Drop in speed on carburetor internal combustion engines

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

If you notice that on such an engine the speed is kept at a fairly high level at idle, the reasons may lie in the following:

• The idle system is incorrectly adjusted. If it has been tampered 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 valve for carbon deposits. A chip or crack is also possible. There is only a replacement;
• Needle valve. The reason is its location. It is possible when an incorrect dosage of fuel enters the chamber;
• Head gasket. She simply burned out. Will have to change;
• The choke is open. To check, you need to evaluate the operation of the damper in the primary chamber. If there is a problem, check the operation of the choke. Usually the problem is solved by lubricating the drive and cable.

These are the reasons that most often appear on cars with carburetor engines when at idle speed remains at abnormal high level. They are also potentially considered in situations where the engine almost immediately.

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

Injector problems

Separately, we should consider situations due to which at XX speeds can increase by precisely injection types engines.

Unlike carburetor internal combustion engines, where the whole problem lies in the mechanical part, the injector has high probability presence of electronic faults.

• Malfunction or failure of the sensor that monitors the coolant temperature. This is the drive to permanent job in engine warm-up mode. You need a diagnostic scanner and probably a controller replacement;
• Malfunction or breakdown of the XX sensor. It's also a mass air flow sensor. Diagnostics will help special equipment. Eliminate broken wiring using a multimeter, replace the unit 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 jump off, causing the engine to behave correspondingly at idle. The unit is returned to its place or replaced with a new one;
• Hall throttle cable. Relevant for older cars. Replacing or lubricating will help solve the problem;
• Sealing gaskets on injectors. They don't get damaged that often. Diagnosing the problem is difficult. They usually check it last.

Be careful when launching and observing the behavior of the tachometer in your car. If you see that the speed is floating, rising to abnormal levels and behaving uncharacteristically, do not ignore such symptoms.

Often, car owners are faced with such a malfunction when, when releasing the gas, the engine speed does not drop, or more precisely, it does not drop to the normal idle level (idle). This applies to both the fuel injection system and the carburetor.

Usually the idle speed of gasoline passenger cars, depending on the engine model, are in the range of 650-1000 rpm. Any deviations from these indicators indicate incorrect operation car power systems. There is no point in delaying the elimination of this malfunction, since increased engine speeds lead to increased fuel consumption in the car and accelerated engine wear, which negatively affects the driver’s financial condition.

Sometimes the reason may lie in excessive enrichment fuel-air mixture supplied to the cylinders. This provokes an increase in speed to a certain level, after which the engine begins to “choke”, thereby reducing the speed to a normal value, after which it rises again. This malfunction causes a “floating speed” effect, but the problem may also lie in other malfunctions of the power system. In addition, do not forget that malfunctions in cases with injection and carburetor engines will be different.

Basic problems with an engine with a carburetor power supply system

• The location of the needle valve, which is responsible for adjusting the gasoline level in the float chamber.
• Insufficient closing of the throttle valve, which often happens when it is clogged or mechanical damage. A dirty valve should be cleaned special means, which can be purchased at an auto parts store. And in case of mechanical damage to this unit, 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, ensuring the optimal ratio of gasoline and air in the fuel-air mixture.
• Consistently high idle speeds may indicate that the throttle valve located in the primary chamber is not tightly closed. This problem occurs due to wear of the throttle valve drive cable or deformation of the valve itself.
• Damage intake manifold or wear of the gasket between the cylinder head or carburetor.

In case of injection system nutrition, possible reasons The increase in idle speed is noticeably greater. This is due to the fact that they can be associated both with the failure of mechanical components and with the malfunction of electronic sensors.

Main injector malfunctions

• Coolant temperature sensor malfunction. Business interruptions of this sensor lead to the fact that the engine constantly operates at high speeds, in warm-up mode. Moreover, 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 air regulator is not functioning properly.
• Throttle adjustment cable stuck. This happens especially often on cars with high mileage.
• Malfunction of the XX regulator or its electronic sensor, while the idle speed may increase or disappear altogether.
• Throttle position sensor malfunction.
• Jumping or overstretching return spring, which should return the damper to its original position.
• Violation of the integrity of the gaskets, rubber seals injectors or the manifold itself. With these problems, excess air from the environment enters the combustion chamber.

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

Let's sum it up

First of all, the malfunction of the injection and carburetor system power supply, you should start diagnosing by inspecting the throttle valve.

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