The idle speed on the engine drops sharply. Engine speed does not drop at idle

11.10.2019

Fuel system

If there is no load, the throttle in the vehicle's motor is fully closed. But the engine continues its work and constantly maintains speed, which makes it possible not to start it again at each stop. This is due to the idle speed controller, as it allows a sufficient amount of air into the intake tract. The breakdown of such a small element can significantly complicate the use of the vehicle, so every motorist should know the principles of the idle speed controller, where it is located and how to identify the reasons for its failure. Information on methods for restoring the idle speed controller will be quite interesting and useful for every driver who is independently repairing his vehicle.

Owners of vehicles manufactured by AvtoVAZ need to know how to check the idle speed controller, because its failure does not cause the “Check Engine” indicator on the dashboard to work.

It is for this reason that owners of domestic cars quite often start checking the car from other components, in particular, the intake system, and only then move on to the idle speed sensor, although in fact, it should be started with it. For owners of foreign cars or modern VAZ models, this problem is not relevant, since a breakdown of the idle speed controller is easily diagnosed using a special scanner and displayed on the instrument panel.

Why float idle

The idle speed controller is often referred to as the XX sensor. It is so small that it fits in the palm of an adult. The idle speed sensor consists of three main parts - a conical needle, which is designed to change the throughput of the pipe, a spring and a stepper motor with a rod.

Such a device is able to change the cross section of the passage channel, which is responsible for the flow of air to the motor during a closed throttle. When the ignition is turned on, the idle speed controller advances the rod automatically until a needle enters the calibration hole. When starting the engine, the idle speed sensor automatically opens the passage, which allows the engine to receive enough air for stable operation. If the coolant temperature is too low, the XX regulator is able to supply more air, providing an increase in engine speed to speed up warm-up. Thus, the vehicle can immediately start without warming up the engine beforehand, without the risk of stalling.

The idle speed control is always located close to the throttle position sensor. You can recognize it by the typical plastic cover of the electric motor, which protrudes strongly above the surface of the unit. A wire runs to it, which connects to a connector nearby or branches off from a joint harness connected to the control unit. Here you need to be more careful, since on modern cars, the idle speed controller can often be located under a common casing that protects the throttle assembly.

No matter how strange it may sound, it is most difficult for the engine to work at low speeds. This happens for several reasons:

1. Fuel is cold and the engine needs to warm up to function properly.

2. There is a pressure difference between the intake and exhaust manifolds, which causes combustion products to be thrown back into the cylinders. This reduces the efficiency of the motor, which provokes rapid wear of parts and increases the percentage of carbon dioxide emissions.

All this is due to the slow flow of the air-fuel mixture into the exhaust system at this stage. Subsequently, it mixes worse, which reduces its effectiveness.

The idle speed of the engine can float for many reasons, but the most common of them can be distinguished:

1. If the needle guides are worn out.

2. If the wire inside the sensor is broken.

How to find out the cause of the breakdown

There are two methods that will help diagnose the cause of the malfunction:

1. We dismantle the sensor and reconnect the four-pin connector. Put your finger on the end of the idle speed regulator needle. You will need an assistant to turn on the ignition. If the XX sensor extended the needle, then it is working and the cause must be sought in the throttle position regulator, since the symptoms of failure are very similar.

2. We dismantle the regulator and use a multimeter to measure the resistance value in the sensor windings. Between contacts A - B and C-D, the coefficient should be in the range of 40-80 ohms. If everything is normal, it is necessary to additionally make cross measurements - between B - C and A - D. The device should show an infinity sign - an open circuit.

Idle speed sensor does not work, how to fix the breakdown

Very often, the reason for the failure of the idle speed controller is its severe contamination. To fix the damage, you need to clean it:

1. Disconnect the wires and unscrew the screws. If the idle speed sensor is fixed with varnish, you will have to dismantle the entire throttle assembly.

2. Wet a cotton swab in a special agent or alcohol and gently wipe the contacts.

3. In case of heavy contamination of the cone needle, spring or stem, WD-40 should be applied to remove deposits.

4. We check the condition of the throttle valve and clean it if necessary.

5. We mount the idle speed controller back and check its performance.

In addition, broken wires can also be the cause of sensor failure. In this situation, it is necessary to clean the contact areas, solder them and varnish this place so that corrosion does not affect the reliability of the assembly. However, not all malfunctions of the XX sensor can be solved by simple cleaning. For example, rod exhaustion, conical needle wear or engine destruction are solved only by a complete replacement of the sensor.

Throttle cleaning

1. We dismantle the device. To do this, we release the throttle body from the air corrugation. Separate the coolant hoses and check that all the liquid has flowed out.

2. Remove the throttle valve gasket and the valve itself.

3. We clean the base of the intake manifold if there is dirt.

4. After cleaning, it is advisable to purchase a new gasket.

5. To clean the throttle, it will be enough aerosols and a regular rag.

6. The spray must be applied to the surface and left for 15 minutes.

Throttle sensor not working, how to change

1. Remove the negative terminal from the battery.

2. Press the plastic latch on the throttle sensor and disconnect the wires.

3. Dismantle the sensor by unscrewing the fixing screws.

4. Install a new throttle sensor in reverse order.

How to clean a carburetor or injector, the progress of work in stages

Cleaning the injector:

1. When the motor is in working condition, remove the fuse that is responsible for its operation.

2. Separate the injector terminals, the injection and reversible fuel line hoses and unscrew the rail with the injectors.

3. Remove the nozzle rings.

4. We take wires with terminals and connect them to a power source.

5. We attach a five-gram syringe to the wide side of the nozzle to ensure a snug fit to the base of the nozzle.

6. We simulate the operation of the valve by pressing and releasing the switch button.

7. After the liquid has been passed through the nozzle several times, it is necessary to leave it for a while and repeat the procedure.

8. We assemble in the reverse order.

Cleaning the carburetor:

1. We disassemble the carburetor, following the safety rules.

2. We put all metal parts in a previously prepared container.

3. Pour the cleaning agent there and wait for a while.

4. We wash all parts under running water, removing all contaminants.

5. We dry all the elements and reassemble them.

Putting the carburetor back together is actually very difficult. Therefore, be patient and collect everything according to the instructions.

Many motorists are faced with the fact that the effect of a drop in idle speed began on the car. Often, this leads to the fact that the engine completely stalls. This effect has many causes that must be urgently eliminated so as not to cause even more problems.

What are the reasons for the drop in turnover?

Many motorists do not look at the condition of their cars at all, and even more so for the engine. Often, the consequences can be expressed in malfunctions, which will develop into a major overhaul, which will pull a large amount of money. Namely, for these reasons, if there are malfunctions with the engine, it is necessary to return normal functionality to it.

So, consider the main reasons that lead to the fact that the idle speed drops:

The adjustment of the screws "quantity" and "quality" is broken

A common cause of low idle on Ozone type carburetors. Often, tightening the fuel adjustment screws is enough to restore normal speed.

Fuel level set incorrectly

In addition to a drop in engine speed at idle, this leads to a drop in power. The motor may stall or start after a long torment. Long-term operation on lean fuel can lead to engine failure.

Foreign air enters the carburetor

"Sucking" excess air can disrupt the operation of the engine. Another option is that the air filter is dirty and not enough air is getting in.

Poor quality fuel

Engines designed to consume high-quality fuel can junk or fail if they are “fed” with lower quality fuel, for example, 92 instead of 95. Moreover, a lot of new problems can fall on the engine that will have to be solved, so it is better to use good gasoline.

On-board computer crashes

It also happens that the on-board computer starts to show inaccurate data. If everything feels fine with the engine, but the electronics persistently indicates a problem, you can try connecting a working BC and check it on it.

Time to change your spark plugs

Determination of the cause of the malfunction

To help determine the cause of the idle speed drop, the following steps will help.

If there are no additional signs of a drop in speed (for example, vibrations), you can check the engine on another on-board computer.
Check sensors.
Inspect spark plugs.
Make sure the fuel and idle levels are adjusted correctly.
Make sure that the carburetor is not "sucking" excess air.
Inspect the air filter for contamination.

Problem Solving Approaches

When all causes are identified, you can proceed to troubleshooting. Of course, there are a different number of ways to solve the problem, but do not forget that a certain sequence of actions is necessary. It is worth considering the issue in more detail.

Adjust fuel and idle levels

Idling adjustment on carburetors of the Ozone type. You will need a tachometer and a slotted screwdriver. It is necessary to carry out work on a warm engine. By turning the "quantity" screw in the direction of the clock hands, you can achieve an increase in speed.

If it is not possible to solve this problem with the help of one "quantity" screw, you need to connect the "quality" screw, on which, if it has not yet been used, there may be a factory plug. It can be pulled out by screwing a suitable self-tapping screw into the plastic and pulling it out.

Adjustment is usually carried out in 2-3 (several) visits.

Replace candles

Even if the candles have recently been replaced, they may be of poor quality or defective. Original spare parts are always better than cheaper analogues. Falling XX often hints at this malfunction.

Change fuel

Using gauges, it is necessary to check the pressure in the fuel supply system and the presence of contaminants. After that, you need to change the fuel to a cleaner and better one. As a last resort, you should think about refueling at the gas station of another company.

Check air and fuel filters

The air filter may be dirty. As the filter gets dirty, the amount of air that enters the engine decreases. Engine power is reduced and fuel consumption increases significantly.

The air filter needs to be cleaned or, more importantly, replaced. It is best to carry out this procedure in advance in order to avoid other problems in the future.

Flush the idle speed sensor

If oil and other contaminants get into the sensor, it fails. The sensor is cleaned with carburetor cleaner and aerosol liquid. The device must be removed and washed. Aerosol liquid gently cleans the needle. Be careful that the liquid does not get into the insides (that is, under the spring), in order to avoid its failure.

Conclusion

The drop in engine speed is a fairly common problem. It can happen not only for any one reason - with severe wear of the motor, it happens that an integrated approach is needed, and breakdowns can be quite specific. In this case, you may need to seek professional help.

Compared to the previous carburetor generation, the new injection VAZ 2114 turned out to be much more efficient and reliable, but from time to time they are also plagued by various problems. Such a situation as a drop in speed after releasing gas on a VAZ 2114 is almost always caused by a malfunction in the injection system, but other causes must be excluded during the diagnostic process.

How to find the cause of the problem

If the VAZ 2114 speed drops, you need to comprehensively diagnose the functioning of the injection system on your car, which can be done in your garage with little experience and appropriate instructions. In this case, those “fourteenths” that were equipped with a dashboard from the German manufacturer VDO have an important advantage in this case, since it, in comparison with the analogue from Schetmash, is equipped with a self-diagnosis mode.

To carry out this procedure, you will need to perform a few simple steps:

after turning off the engine, it is necessary to hold the odometer button pressed for three to five seconds;
after moving the engine ignition to the first position, the button must be released;
arrows should appear on the display, which is a signal of normal operation, then the button must be pressed the first (displaying the firmware version) and the second time - after that, probable errors in the computer will be shown;
to reset the error message, you will need to hold the button until zero appears on the display.

After reviewing the manual, you can find out what errors shown on the screen may be due to the fact that the speed is constantly dropping when the gas is released on the VAZ 2114.

So, it could be one of the following situations:

code 1 - controller error;
code 14/15 - coolant sensor error;
code 22/23 - throttle position sensor error;
code 33/34 - mass air flow sensor error;
code 42 - faulty ignition;
code 44 - lean or too rich fuel mixture.

The owner of the VAZ 2114 should remember the specific features of the self-diagnosis mode on his car: if there are several errors, the computer sums up their codes arithmetically, which can be misleading. This may be indicated by the logical inconsistency of the displayed code with the actual problems.

To be completely sure, you will either need to take the car to a service and pay for its inspection, or buy a diagnostic scanner yourself, which is not so expensive. Another option is if you have the same VAZ model (fully serviceable), take turns removing potentially vulnerable sensors from it and putting them on your car, looking for a problem by elimination.

Finding a breakdown without using an onboard controller

External "symptoms" of the behavior of a car and, in particular, its engine can also give a lot of food for thought to an experienced and observant driver. By analyzing these factors, you can significantly reduce the list of probable causes of the problem.

For example, it is necessary to track the moment of arbitrary engine shutdown - at idle, at a "cold" start, after the engine has warmed up to a specific temperature, or when the gas pedal is pressed sharply.

In addition, you should pay attention to whether the speed drops with constant gasping, and how does the engine behave when braking, releasing the gas pedal and disengaging the gear?

Along with visual and auditory diagnostics, it would be useful to check potentially vulnerable nodes in a circle that can cause the VAZ 2114 to stall when the gas is released.

Firstly, you should start by checking the fuel and air filters - it is recommended to change them every 30 thousand kilometers, but in fact, the operating conditions and the quality of the filters lead to the fact that it is better to halve this period to avoid problems (especially since cars with high mileage filters become clogged even faster).

In addition, it is imperative to check the fuel level in the tank, no matter how ridiculous it may sound: the fuel level sensor often deceives the driver, and besides, the car can simply stand on a slope, which is why the fuel pump simply does not supply fuel to the engine - hence reason for the drop in turnover.

A very common situation is the appearance of problems with ignition or holding speed after a minor self-repair: in this case, you need to check all the chips, contacts, terminals and wiring again to exclude the usual human factor.

RPM drop in neutral

If the speed drops on the VAZ 2114 and the engine stalls “cold”, there are not so many probable causes of problems: a failed gas pump, a breakdown of the idle speed controller, a clogged injector, or a malfunction of the coolant temperature sensor.

The main ways to deal with the situations encountered are as follows:

1. If the cause is in the idle speed controller, then the engine will constantly triple in this mode, and not just stall. To diagnose the IAC, you will need a multimeter, which, when the engine is turned off, measures the resistance: on terminals A - B, C - D it should be approximately 54 ohms, while between the pairs it will be equal to infinity. Any deviation from these indicators should be considered a malfunction.

1. A dirty injector is a very common situation, considering how low-quality gasoline is sold at most gas stations: sometimes using a special injector cleaner can help. It is worse when the nozzles are clogged - if the cleaning products did not help, you will have to change them or take them to the service for cleaning.
2. The failure of the fuel pump is usually preceded by characteristic signs of violations in its functioning: an attentive driver, long before the breakdown, will hear a difference in the sound of the pump when the engine is started. If at the same time the problem with a stalling engine is not present when driving in gear, but occurs at idle, you can first check the fine filter.

Sometimes candles can fail, which directly affects the operation of the entire ignition system, but their regular replacement for preventive purposes prevents a problem in advance. Additionally, it is recommended to check the condition of the ignition coil.

Malfunction of sensors

The normal functioning of the injection engine on the VAZ 2114 is ensured by the correct operation of four key sensors: throttle position, mass air flow, crankshaft position and coolant temperature.

Throttle position sensor VAZ 2114

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 carburetor problems. 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 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. 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 diagnostics 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.

Possible reason

The rpm drops when the brake is pressed due to various malfunctions in

To find out the cause more accurately, you need to know how this node is arranged. Knowing how this amplifier works, and faced with such breakdowns, it will be easier to solve the problem.

vacuum booster

If the engine speed drops when the brake is pressed, the vacuum booster or its component parts are to blame. Often this problem happens due to the design features of this mechanism and the principle of its operation. This mechanism is located in a round closed case. It is located under the hood, not far from the brake pedal. The master cylinder is connected to the body. The main task of this node is to reduce the pressure force on the pedal when deceleration is performed. At the heart of the amplifier is the diaphragm.

Diaphragm

This part is quite elastic and at the same time durable. It is made of modern polymer materials based on polyurethane. In the central part of the diaphragm there is a steel part in the form of a circle, against which two rods abut from different sides. One of these elements is connected to the pedal.

The second - with the main diaphragm divides the body into two parts. One of these parts is vacuum. It is located on the side of the master brake cylinder. The second is the atmospheric half and is on the other side. The vacuum brake booster is sealed. Its body with a diaphragm inside is rolled. The two halves are connected to each other by means of a working valve. The brake pedal is used as a drive for this valve.

Principle of operation

The main task of the amplifier is to maintain a vacuum in two communicating chambers at a time when the valve is open and the brake is not pressed. If you press the pedal, the element will close. In this case, a powerful rarefaction will occur in the part responsible for the vacuum. To obtain this vacuum, a pipeline is connected to the chamber fitting, leading to the intake manifold of the power unit. Also in the design of the mechanism there is a return spring.

It returns the diaphragm to its normal position. When the driver presses the pedal for the first time, the valve closes. If you continue to press, then a hole will appear in the atmospheric chamber and air will get there. The pressure inside the chamber is 760 mm Hg. Art. Due to the rarefaction, the pressure on the master cylinder rod will increase, and therefore the braking efficiency will increase. This principle of operation of the amplifier is relevant only for gasoline engines. On diesel engines, getting a vacuum in this way will no longer work. Therefore, automakers equip amplifiers for diesel units with special pumps.

Relationship between crankshaft speed and brake booster

As noted above, the vacuum booster is in direct connection with the intake manifold. Therefore, any violation of the tightness of the manifold will adversely affect the quality of the air-fuel mixture that enters the engine cylinders. An air-fuel mixture where there is not enough oxygen will not burn completely. Therefore, the power unit loses power and efficiency.

That's why when you press the brake pedal, the revs drop.

Diagnostic methods

If such problems occur during the use of the car, you must immediately find out what exactly the malfunctions are. The fact is that the situation when the speed drops when you press the brake is very unpleasant. If at first the speed only drops slightly, then after a while the engine will simply stall when the brake pedal is lightly touched. It can happen at the most inopportune time. Note that even in a fully serviceable car, the speed drops when you press the brake, but this drop is insignificant. This happens due to the design of the amplifier.

Hose

When the RPM drop is quite significant, then it is necessary to carefully visually inspect the hose connecting the booster and the intake manifold on the engine. If there is visible damage on the tube, and these may be various cracks or tears, then the tightness of the collector is broken. What is the result? The process of normal preparation of the fuel mixture is changing, which is why the stable operation of the engine is disturbed. That is why when you press the brake pedal, the speed drops and the engine stalls.

If the hose is damaged, it is recommended to replace it. And then the problem will be solved. If the tube is perfect, you should look in the manifold fittings and in the vacuum booster itself. If this does not help solve the problem, then the cause should be sought in the amplifier itself. But it must be remembered that it will not work to repair the vacuum brake force mechanism. It is not repairable, and therefore the issue can only be resolved by a complete replacement.

Typical vacuum booster problems

Before talking about the malfunctions of this system, it should be noted that a breakdown of the mechanism does not completely disable the system. The brakes will work, but driving a vehicle with a faulty power assist will require more effort to slow down.

In this case, when you press the brake, the speed drops. One of the most popular breakdowns is a broken hose. A characteristic hiss will be heard from under the hood. What to do in this case, has already been said above. Breakdowns inside the amplifier mechanism are also possible. The valve may fail. During operation, it hardens, and due to rubber wear, the diaphragm and the elastic partition may collapse.

Diagnostics of the vacuum booster

So, if a drop in speed is noticed when the brake is pressed, then the first step is to check the amplifier for serviceability. Of course, you can go to a carburetor specialist. But this is unlikely to solve the problem of falling turnover. If there is a depressurization, then this will lead to air entering the intake manifold. As a result, the speed drops when you apply the brake. The fuel-air mixture is sharply depleted. There is also another diagnostic method. The brake pedal is pressed up to six times with the engine off. Then the pedal is fixed in the middle position and the engine is started.

When the pedal will fail during the start-up process, then everything is in order with the amplifier. If it remains in the same position, special attention should be paid to the element. During a visual inspection, it is necessary to look for leaks on the body and the cause of the leaks.

Replacing the vacuum booster

Replacing this mechanism is quite simple if you have the necessary tools. In various vehicles, it may be necessary to dismantle the expansion tanks. During the operation, the brake cylinder is removed, and then the amplifier itself. It takes approximately three hours in total.

Summary

A vacuum booster is an important thing to do in any car. It makes braking easy and effortless. That's why when you press the brake, the revs drop. The reason is a faulty amplifier or system depressurization.