Often, car owners are faced with such a malfunction when, when the gas is released, the engine speed does not drop, more precisely, it does not drop to the normal idle level (XX). This applies to both the fuel injection system and the carburetor.
Usually the idle speed of gasoline passenger cars mobiles, depending on the model of the motor, are in the range of 650-1000 rpm. Any deviations from these indicators indicate incorrect operation of the vehicle's power system. It is not worth delaying the elimination of this malfunction, since increased engine speeds lead to an increase in fuel consumption in the car and accelerated engine wear, which negatively affects the financial condition of the driver.
Sometimes the cause may lie in the excessive enrichment of the 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 they rise again. This malfunction causes the effect of "floating revolutions", but the problem may lie in other violations of the power system. In addition, do not forget that malfunctions in cases with injection and carburetor engines will be different.
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.
- Leaky closure throttle valve, which often happens when it is clogged or mechanically damaged. Dirty damper should be cleaned special tool which 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 to the intake manifold or worn gasket between the cylinder head or carburetor.
In the case of an injection power system, possible causes the increase in idle speed is noticeably greater. 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 speed at Idling may increase or disappear altogether.
- 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 the case of an injection engine, it will help to accurately determine the malfunction of a particular sensor. computer diagnostics. To do this, it is best to use the services of a service that specializes in servicing cars of a particular brand.
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 to power unit worked steadily 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 carburetor machines, the engine speed does not often drop 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 a high level of fuel in the carburetor's float chamber also leads to 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 the problems, injection system more difficult, 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. A frequent cause of this 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 the use of 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 revs XX, 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.
Read also
Why does the engine have high idle speeds. The main reasons for the high speed of the twentieth on the injection motor and engines with a carburetor.
High engine speeds at idle, in addition to completely unnecessary excessive fuel consumption, also make it difficult to drive a car - for example, when driving through a particularly broken section of the road, when you want to carefully “sneak” among the potholes in first gear, and the car boldly takes hits on the suspension. In addition, during prolonged downtime in traffic jams, the engine will always operate at elevated temperatures.
Consider several reasons why increased idle speeds on a warm engine do not fall. The reasons may be malfunctions in both the mechanical and electronic components of the engine power system, so we will describe possible options breakdowns separately. But since these components interact in a complex in a car, you may be able to independently find the answer to the question of why your engine has high idle speeds, taking the material of this article as “information for thought”.
Checking the intake manifold for leaks
Excess air intake can cause high idle speeds. Moreover, depending on the place where excess air enters the intake manifold, the idle speed will either simply be increased, or they will begin to "float" -.
If the idle speed "floats", then most likely it takes place.
If there is simply a violation of the tightness of the intake manifold gaskets, damage to the vacuum hoses or sealing rings, then the speed will “float”. This happens due to the fact that the amount of gasoline supplied to the cylinders will be constant, and the quality of the mixture will become “richer” or “poorer”. Upon reaching a certain critical value (air content in fuel mixture) the motor will start to slow down - up to a stop. But with a decrease in the number of revolutions, the amount of air entering the manifold will decrease, that is, the mixture will be enriched and the engine will “come to life” - the idle speed will increase. This will continue until the intake manifold is sealed.
On turbocharged engines, air can also be sucked in through damage to the intercooler or air pipe connections. With significant suction (for example, if the pipe has come off the intercooler), the engine starts to work with a whistling (or hissing) sound. But sometimes it is possible to identify the place of violation of the intake tract only by blocking the air supply to the intake manifold in different places in turn - from air filter up to the collector.
Excess fuel supply
Throttle cleaning
A completely different situation will turn out if not just excess air, but an air-fuel mixture flows - for example, through a gap formed as a result of a loose throttle closing. In this case, high idle engine speeds will be stable.
In the fuel systems of some engines, semi-automatic fuel supply control is provided in the engine warm-up mode - due to it, high idle speeds are maintained until the engine warms up to a predetermined temperature. Fuel is supplied through a channel that "bypasses" the throttle valve.
Such a channel can be closed/opened different ways- the valve in it has either an electric drive (solenoid), or it can be arranged like a refrigerator thermostat - when the engine warms up, the channel is blocked.
At high idling you should check the entire throttle assembly with sensors and the XX regulator.
In any case, such a valve can break, and then excess fuel will always enter the intake manifold, which will cause high speed idling after the engine has warmed up.
In all such cases, first of all, you need to remove the throttle body and rinse it with a special solution - a lot of such "chemistry" is sold in stores. After washing, you need to carefully inspect the assembly - especially for sticking or, on the contrary, excessive looseness of the throttle.
The throttle valves of some injection engines also have a screw for adjusting the engine idling speed or limiting the closing of the damper - you should also pay attention to them - whether the assembly can be adjusted.
Often, the engine speed does not drop at idle due to the “gas” cable sticking or foreign objects getting under the pedal - the corner of the rug, for example.
Of course, almost all of the above can apply to carburetor engines. Besides, characteristic malfunction(or, more precisely, a deviation from the norm) for them is incomplete opening air damper- mainly due to improper installation of the "suction" cable. In the absence of breakdowns, the normal idle speed of the carburetor engine is set by adjusting with two screws - the "quantity" and "quality" of the mixture.
Electronics failures
Checking the engine idle speed control
After replacing the idle speed controller, it must be “registered” i.e. enter its parameters into the memory of the computer.
The idle speed controller (IAC) is stepper motor(solenoid), powered by pulse signals supplied. It works in a similar way to the screw for adjusting the amount of mixture in the carburetor - when the valve is extended, it closes the fuel channel, and when it moves back, it opens it.
It often happens that the regulator core simply jams, and it stops responding to ECU signals. Moreover, you can damage the idle speed regulator even in the store when buying - trying to turn or push the valve needle with your hands.
If after replacing the idle speed sensor (regulator) there are high speeds, then most likely it is either the computer or the mass air flow sensor - all the elements that make up the power system work in cooperation, and diagnostics need to be carried out. It is quite possible that you will have to "prescribe" a new regulator - that is, enter its parameters into the computer's memory.
temperature sensor
This sensor can also affect the engine's fuel system. By issuing an incorrect signal (corresponding to a low temperature) to the ECU, it will cause the controller to give a signal to other elements fuel system(injectors including) about the enrichment of the mixture. Incorrect sensor signal will cause the idle speed to be more than 1000 min-1.
Mass air flow sensor
The DMRV directly affects the quality and quantity of the mixture supplied to the cylinders - after all, the ECU “knows” about its composition thanks to this (and some other) sensors.
In conclusion, if the idle speed of your car has risen for no reason, first look for the cause in possible jamming of the fuel system mechanisms - after all, it is they who are primarily exposed to various contaminants, and for electronic components, power surges or short circuits are much more dangerous.
Often drivers are interested in why the engine speed does not fall at idle. This situation is quite common, and neither carburetor engines nor more modern injectors are immune from this. True, the causes of the malfunction will be different for them. But, in practice, everything can be diagnosed independently, and also on almost all car models, the problem can be fixed by hand without much difficulty. The most important thing here is to correctly diagnose, this will significantly speed up the repair process, and save you from additional problems and difficulties.
What it is?
Why does the engine speed not drop at idle? To begin with, let's decide how to understand that a problem has arisen, and also see what it can lead to. Even an inexperienced motorist can determine the increase in idle speed. This is easy to hear. With an increase in speed, an increase in the noise of a running engine with the gas pedal released is observed. Also on machines equipped with a tachometer, you can trace the increase in speed on the device. On almost all models of passenger cars, idle speeds fluctuate within 650-950 rpm(specify the indicator in the data sheet of your car), everything above is considered a deviation from the norm. Also on many injectors, this problem causes the inclusion of a “check” on the panel.
In any case, the problem should be fixed as soon as possible. Increased speed is the reason for the increase in fuel consumption. This increases the cost of refueling. Also, an increase in speed significantly accelerates engine wear. So it is not advisable to delay the solution of this problem. This way you save a lot of money. When identifying and eliminating the cause of high speeds, it should be remembered that on carburetors and injectors, the problem can be caused by various malfunctions.
carburetors
First, let's deal with the problem on carbureted engines. This type of food is considered obsolete, but many cars on the roads are still equipped this way. Also, many motorists, for their own ideological reasons, use such motors, and are not going to refuse them. Diagnosing the source of the problem here is quite difficult, and this is given the small list of elements that cause an increase in speed. Let's look at what you should pay attention to:
- Seizure of the needle valve. In this case, the fuel enters the chamber is not metered. Moreover, depending on the location in which the valve is stuck, idle speed can both disappear and vice versa increase;
- Violation of regulation idle systems. This usually happens after cleaning or repairing the carburetor. To avoid problems, you should correctly set the ratio of fuel and air supply. If you have not previously produced, then it is better to read how this is done exactly on your version;
- Closing problem. There may be several reasons for such a malfunction. Most often, the damper does not close due to the presence of soot on it. In this case, you will need to clean up this node. Usually, this helps. In some cases, the throttle valve may be damaged. Then you will need to change this part, but not all carburetors have this feature;
- Sometimes, the problem can manifest itself when, this happens quite rarely. But it's still better to check. To do this, with the engine running, open the radiator cap; if the gasket is burned out, White smoke. In this case, you will need to change the gasket;
- Open suction. Check how the damper works in the primary chamber. If a problem is identified, then it makes sense to see how the suction works. Most often, to fix the problem, it turns out to be enough to simply lubricate the cable and damper actuator.
Injector
On engines that are equipped with injectors, there are more possible reasons for increased speed. In particular, the problem can be caused by both mechanical failures and failure of electronic sensors. But, unlike simpler carburetors, it is simplified by the presence on-board computer which is capable of reading errors. So, consider the reasons for the increase in speed on the injectors:
- Refusal . If this sensor breaks down, the power unit starts to work non-stop in the warm-up mode, that is, the speed is not reset. The control unit considers that the optimum operating temperature has not yet been reached and tries to heat up the unit. Such a malfunction is fraught with engine overheating and costly repairs. The easiest way to identify this problem is with the help of computer diagnostics;
- Work disruption. Sometimes, the cause is the mass air flow sensor. Again, they make diagnostics, after which they check suspicious sensors with a multimeter. An additional check is required to rule out a broken wiring. If necessary, faulty sensors are changed;
- there may be a stuck throttle cable. Check if it works. If a malfunction is detected, it is recommended to try to lubricate the cable and develop it. If it does not help, then you will have to replace the part completely;
- The damper return spring has jumped off, or the damper return spring has stretched too much. This problem is also typical for older cars. Put the spring in place. If it is stretched, then you will need to buy an injection repair kit;
- . In this case, it sends an open throttle signal to the engine control unit, in turn, the “brains” of the car provide more revolutions than is actually needed. The cause of the failure may be a simple jamming of the part, or burnout of the resistance. In the latter case, only the option of replacing the sensor is possible;
- The last reason to check is integrity. injector seals. The check will require a fairly serious intervention in the injector, therefore, this reason is checked last, although this phenomenon is not the rarest. If the gaskets are damaged, excess air enters the combustion chambers, which causes an increase in engine speed.
Conclusion. Every motorist has encountered problems with the operation of the power system at least once. Therefore, such a question, why the engine idle speed does not fall, is not surprising. Unfortunately, it is almost impossible to answer it unambiguously. There are many reasons for this behavior of the car. To identify and fix the breakdown, you will have to conduct a detailed diagnosis.
During the operation of the car, drivers have to deal with various problems. One of the faults, which is quite widespread, is the constant maintenance of high engine speeds. That is, even at idle, the engine speed does not fall. Such a problem can be observed both in injection and carburetor engines, but the reasons for this will be different. In this article, we will consider what a symptom of what kind of malfunction this problem is, and how you can get rid of it.
Table of contents:How to diagnose that idle speed is not falling
Even an inexperienced driver can easily notice that at idle speed of the car, the speed does not drop easily. This is easy to determine by ear, because, as you know, the lower the speed, the quieter the engine runs. In addition, if the car is equipped with a tachometer, it can be used to determine the number of revolutions per minute at a particular point in time.
Depending on which engine is installed in the car, the rate of revolutions per minute at idle may vary. On average, it is generally accepted that the engine is running normally when the idle speed is between 650 and 950 per minute. If RPM is higher (unless otherwise stated in technical passport to the car), then this can be called a deviation.
Please note: On most fuel injected vehicles, the "Check Engine" light on the instrument panel will come on at high idle.
What causes high idle speeds
The first thing the driver should remember is the high fuel consumption at high speeds. Accordingly, if high speeds are maintained at idle, this means that part of the fuel "flies into the pipe." Moreover, this problem directly affects the resource of the engine, which suffers as a result of such a malfunction. The node itself, which led to the occurrence of the malfunction in question, may also suffer. That is why, if this problem is identified, it should be fixed as soon as possible.
Why the idling speed of the carburetor engine does not fall
At the moment, carburetor engines are practically not used in modern cars. However, you need to consider why a high idle problem can occur in such engines, since most of the problems overlap with injection engines. When such a malfunction occurs, pay attention to the following items:
Most of the problems that lead to high idle speeds in a carbureted engine are discussed above. Also, a common problem for carburetors and injectors cannot be ruled out - jamming the gas pedal.
Why the idle speed of the injection engine does not fall
Now consider the malfunctions that lead to increased idle speed in an injection engine. Unlike carburetor engines, where all the problems are mechanical in nature, a malfunction in the injector can be associated, among other things, with incorrect operation of the electronics. The main reasons are as follows:
As you can see, there are a lot of problems due to which idle speed does not decrease. If such a malfunction occurs, you should start looking for its cause as soon as possible in order to prevent even more serious problems.