Idle speed instability is a very common malfunction of the fuel system of internal combustion engines. The situation itself, when the speed is jumping, has no harmful consequences, but, as a rule, if you suddenly release the gas pedal when shifting to neutral, the car engine can stall. With heavy traffic, stopping in a traffic jam or at an intersection, this is fraught with an accident. Therefore, identifying the cause of the breakdown and eliminating it is a top priority.

Injection and carburetor internal combustion engines have practically the same reasons for idle instability, but they are caused by defects or improper operation of completely different units, since the organization of the supply of the air-fuel mixture to the cylinders differs significantly.

Common causes of idle instability

Injection and carburetor engines have almost the same ignition system. The most common cause of failures is related to damaged spark plug wires. Their device is such that it is not always possible to check the serviceability yourself. Moreover, a removed and stationary wire can show the correct resistance values, and work unstable during vibration. Insulation breakdown can sometimes be noticed in the dark by the bluish glow in damaged areas. The best test is to install a known good ignition wire. If the engine's performance has changed for the better, then the high-voltage wires need to be replaced. When the engine speed drops in wet weather, the spark plug wires are also likely to blame for this.

In carburetor engines, the ignition distributor may be the culprit.

Turnover fell when air was sucked in

Why is the turnover falling in this case? Sometimes the engine speed will jump when air leaks from the carburetor or MAF sensor. In the carburetor power system, this causes a depletion of the working mixture, and in the injection system, according to the readings of the air flow sensor, one quantity enters the cylinders, but in fact a little more, which also depletes the working mixture.

To check, you need to use an aerosol to wash the carburetors. It needs to be sprayed on suspicious joints while the motor is running. A change in the nature of work (usually the speed rises sharply) will indicate the place of air leakage.

In engines equipped with an oxygen sensor (lambda probe), the source of problems may be air leakage in the exhaust tract in the area before the lambda probe. He, determining the excess air after the combustion chamber, considers that the mixture is lean, and increases the fuel supply, as a result of which, accordingly, the engine speed of the car floats.

Idling system malfunctions of carburetor engines

In older units with a carburetor, the most common cause of failures is clogging of the idle jets with unfiltered particles in the fuel or resin deposits that also get along with the fuel. In carburetors with an idle solenoid valve, it is the valve that can cause the system to malfunction.

To check, remove the power connector from the valve with the engine stopped, and after turning on the ignition, put it back in place. The absence of a characteristic click will indicate a malfunction of the solenoid valve.

To flush the carburetor at home, you can use a flushing fluid in an aerosol can.

Idling system malfunctions of injection engines

In injection cars, the idle speed control is most often the culprit for the idle speed jump. This is a rod whose height is adjusted by a stepper motor. Stem contamination with resin deposits from low-quality fuel is most common. At the same time, the rod moves abruptly, in jerks, in certain areas it can completely stall, while the idle engine speed floats. Deposits are washed off with carburetor washing fluid.

Strictly speaking, almost all sensors can influence idle instability. Starting from the mass air flow sensor and ending with the lambda probe. It is more convenient to search for a faulty element using the diagnostic system. If the car is equipped with an on-board controller, then it will have the error code received in this device. By the code, you can determine which of these elements is faulty.

Checking the camshaft and crankshaft position sensors

Some sensors can be checked with a voltmeter. They are MAF sensor, camshaft sensor and crankshaft sensor. The last two are diagnosed by connecting a voltmeter to ground and a signal wire with the ignition on, but the engine not running. When the crankshaft rotates slowly, the device will show periodic voltage surges. If the crankshaft sensor is faulty, the engine will most likely not start, but with an inoperative camshaft sensor (phase sensor), the engine will work. Only in this case, the idle speed floats, and when driving, dips or an arbitrary increase in speed are possible, since the power system switches from the phased injection mode to the simultaneous injection mode, and the revolutions jump regardless of the driving mode.

Checking the MAF sensor

To check this element, you need a digital voltmeter with a measurement limit of 2 V. The voltmeter is connected to the signal terminals of the DMRV when the ignition is on. In particular, at VAZ, these are terminals 1 and 3. The voltage value of a serviceable element should be in the range of 0.99-1.01 V. A voltage of more than 1.05 V indicates its failure. In this case, interruptions in the operation of the engine in all modes are possible.

The sensor in question cannot be repaired. The ingress of moisture onto it when flushing the sensitive element is guaranteed to disable it.

Floating revolutions with a faulty oxygen sensor

The oxygen sensor, or lambda probe, measures the oxygen content in the exhaust gases and, on the basis of the data obtained, determines the parameters of the quality of the working mixture, giving a signal for its depletion or enrichment. The device works normally only after it warms up to an operating temperature of at least 300 degrees. Therefore, most of them are supplemented with an indirect heating system to speed up the transition to operating mode. Malfunction of heating or contamination of the working surfaces of the sensors with combustion products cause inaccuracies in determining the oxygen content, as a result of which the engine will be unstable.

temperature sensor

The electronic control unit (ECU) increases idle speed when starting a cold engine, since at low temperatures the engine is unstable and can stall. As the temperature rises, the ECU gradually slows down and brings them to a minimum when the minimum operating temperature is reached. To measure it, a coolant temperature sensor installed on the cylinder block is used. It should not be confused with the temperature sensor installed on the radiator, which is used to turn on the fan.

The temperature sensor is checked by measuring its resistance with an ohmmeter. A serviceable element at room temperature has a resistance of several tens of kilohms, and when heated to 200 degrees (you can carefully use a lighter), it falls tens of times. If, when the sensor is heated, the readings of the device do not change, then we can conclude that it is faulty.

Conclusion

We have considered several situations in which the engine speed floats. To solve the problem, having accurately established its cause, it is better to contact the specialists at the maintenance station.

A drop in engine speed is quite an unpleasant incident for your car. This is not only about the inconvenience and questions about the health of the machine, but also about the operation of important mechanisms. The problem is that a sharp drop in idle speed, when the car is rolling in neutral, can shut off the engine, and this becomes dangerous for further movement. The driver may not notice such an incident, engage second gear and release the clutch, which will cause sudden engine braking. The car can start "from the pusher" in this way, or it can simply stop, which will create an emergency. When the car warms up, a drop in rpm also has an unpleasant effect on driver confidence. You have to constantly gas up your foot or use other methods to keep the engine in working order. It is worth understanding the causes of the problem.

So why does the rpm drop when warming up on cars with a carburetor? You can find many common reasons that unite the owners of both a specific car model and a specific type of carburetor. I must say that today cars with this type of fuel injection are no longer produced. This is not the best solution, since the carburetor is very sensitive to the quality and purity of fuel, often requires maintenance and does not serve very well in different climatic conditions. This type of petrol injection requires stability, but in our operating conditions it is simply impossible to provide such a luxury to a car. Therefore, various problems arise that can lead to significant discomfort and even the danger of driving. Today we will look at the main reasons for a sharp or wavy drop in rpm during warming up on cars with carburetor fuel injection.

Perhaps it's not about the technology, but about the gas station?

As mentioned above, the carburetor is very sensitive to the quality of the gasoline that you put into the car's tank. If specks or impurities are found, the equipment will not be able to work normally. Dirty gasoline is cleaned up to a certain point by a filter, but over time, such cleaning stops helping. Fuels with impurities and inclusions can be a big problem that affects more than just revs. Here are some important indicators of such a problem:

• within a few kilometers after refueling with low-quality gasoline, you will feel changes in the dynamics of the car, fuel consumption will increase and stability will deteriorate;
• engine idle speed can float, and this will indicate an unstable composition of the fuel mixture; at speed, small jerks and dips in the thrust of the unit are also possible;
• after the engine has cooled down, at the next start, heating may start unexpectedly from low revs, you will have to play with suction in unusual ranges for warming up;
• it is also quite possible that after warming up to 30-40 degrees, a failure will occur, which will need to be compensated for by pulling out the suction all the way or by gassing with the foot;
• when it warms up to operating temperature, the engine will work relatively stably, but the speed will remain floating, these are the indicators of low-quality fuel in the car's tank.

These criteria indicate that it is better not to go to the gas station you are used to. Of course, the same problems are possible in case the carburetor fails and needs service. But often these problems arise precisely when low-quality fuel with a low octane number or with impurities. Therefore, the first step is to roll out the gasoline on a warm engine and add good proven fuel to it.

Time to service the carburetor - minor defects

Small breakdowns in the carburetor system can also cause a drop in speed during warming up. These are ruptured diaphragms, misaligned cable fasteners or a jammed damper drive. Such troubles can be cured by revising this device. In the old days, every second car driver could independently sort out the carburetor, install a repair kit and drive on, listening to the pleased rumbling of the unit. Today, the repair principle is as follows:

• you should go to a car store or market to find a suitable repair kit for your type of carburetor, it is better to take original quality parts;
• further, it is important to find a master who is well versed in carburetors and can help with the elimination of problems in your device, there are less and less such masters in cities;
• in a few tens of minutes a specialist will sort out the equipment, find the problem and install new gaskets, membranes, seals and other products from the repair kit;
• then it is necessary to check the equipment to make sure that there are no unpleasant effects, often this can only be done the next day on a cooled car;
• the last step is regular visits to the master 1 time in 2 years for maintenance and revision of the carburetor, this will keep the car in good working order for a long period.

Carbureted fuel injection has its advantages. Maintenance and cleaning of the injector will cost a fortune. But the repair of the carburetor, even with the replacement of certain parts, will not be too expensive. But to obtain these benefits, you should find a master who is well acquainted with the features of your particular car model. Such a specialist will help fix all problems and continue to operate the machine without problems.

Condensation or dew point - is this possible?

On VAZ 2107 cars, a drop in engine speed very often occurs during warming up until the unit stops completely. This trouble is typical for all carburetors, except for the Solex. The problem is that at temperatures from 0 to +5 degrees, condensation can collect in the carburetor chambers. This is a specific type of dew that forms with temperature changes. After starting the engine to cold, the following process occurs:

• first, an open suction starts an enriched mixture, which burns without problems and does not cause tangible changes in the operation of the power unit, which is very important for a normal start;
• as the car warms up, the car owner lowers the suction, the mixture approaches the working one, and the entire engine system is already a little warmed up, and here the most interesting thing begins;
• condensate or dew begins to get into this mixture and change its properties, in some device models this happens quickly and unpleasantly, causing the motor to stop;
• the driver pulls out the suction again or presses the gas pedal, the mixture is enriched, the engine works normally, but up to 60-70 degrees this process can be repeated endlessly;
• after warming up to approximately the operating temperature, everything is normalized, the speed returns to normal, the engine works well, so when visiting the station, the master will not find anything.

How to deal with such a situation is difficult even to imagine. The only effective way would be to replace the carburetor with Solex, but these models often have problems with starting the power unit in transition temperatures. So it is not easy to give any specific advice in this case. It is best to service the equipment on time and always keep the fuel equipment in good condition, this will help to get the proper reliability of the machine.

Are there any other reasons for the sharp drop in revs?

There can be a whole variety of reasons for such a nuisance. If you are repairing a car yourself, you should take a broader look at the trouble and try to find the reasons in other nodes. But it is worth moving to other features of the car only if you are convinced of the high quality of the carburetor, normal fuel and other features mentioned above. Here are some more ideas to test:

• fuel filters - very often the filter elements become clogged, and the owners forget to change them in time, and this leads to serious problems with the vehicle;
• thermostat - perhaps after a slight warming up of the small circle, your thermostat opens and lets a sharply icy liquid into the engine, which leads to a drop in speed;
• electronics - it is worth checking the ignition, the correct installation of the timing belt, the absence of problems with sensors and various electronic equipment on board your car;
• turning on electricity consumers - perhaps some powerful device is automatically turned on in your car, which gives a load to the unit, the revolutions inevitably fall;
• valve system - there will be no sharp drops and drops in this case, but floating and unstable revolutions are quite possible, and under load they will turn into drops.

There can be a lot of reasons for engine instability. Sometimes the problem is that the generator stops supplying normal voltage at a certain point, which affects the operation of the engine's electrical systems. The load on the engine can also be due to poor oil or internal failures in the cylinder block or in the valve system. So digging in this case can take quite a long time, but it is better to visit a service station and find the cause of the problem.

We suggest watching a video with a solution to one of the possible causes of this problem:

Summing up

There are dozens of breakdowns that lead to a sharp or gradual drop in revs on carburetor cars. But the question is that the equipment turns out to be quite demanding for maintenance, so all the reasons combined have to be eliminated. If you always encounter such a problem, then this is the specifics of the carburetor installed in your car. Most likely, only replacing the device will help get rid of the troubles. If the trouble occurred only a few times, you should try to service the fuel system, replace the filter and install a new carburetor repair kit.

Cars with this type of injection are gradually giving way to injection systems. They are more reliable, more economical, last longer and do not bring the hassle of carburetors. Of course, direct injection also has many subtleties and features to keep in mind. But changing a carburetor to an injector is too laborious and expensive process. It is better to properly service your equipment and get it working properly. Even with very good service, within 1-2 years you will have to go to service again. Have you ever experienced a sharp drop in engine speed during warm-up?

During the operation of the car, many owners face a number of problems. One of them is a decrease in engine power. At the same time, it is not always clear what is the reason for this phenomenon, what measures to take, whether it is worth going to the service station. Let's talk about the main reasons why the engine does not pull and how you can fix the problem on your own.

The main reasons for the decrease in engine power

1. Malfunction of the crankshaft position sensor

There are situations when the DKPV untimely sends a control command to supply the air-fuel mixture. As a result, the power of the power unit drops before our eyes. The main cause of the failure is the shift of the sprocket in relation to the pulley and the damper delamination. In such a situation, it is necessary to carefully inspect the damper and replace it.

2. Increase (decrease) the gap between the electrodes of the candles

During operation, due to the powerful temperature effect, the distance between the electrodes of the candle may decrease or increase. To exclude or confirm your suspicion, you need to check the size of the gaps with a round feeler.If the distance is less or more than the allowable, you need to adjust by bending the side of the electrode or replace the spark plug. As for the optimal distance of the spark gap, it can be different (depending on the type of spark plug) - 0.7-1.0 mm.

3. The appearance of carbon deposits on candles is another clear sign of a problem.

If the engine pulls poorly, it is necessary to unscrew all the spark plugs one by one and inspect them. If obvious carbon deposits appear on the electrodes, the device must be cleaned with a metal bristle brush. In this case, it is important not only to clean the candles or replace them, but also to find out the cause of this phenomenon.

4. Failure of spark plugs

Decreased engine power may be caused by product failure. In this case, it is necessary to check the performance of the candle on a special stand. If the suspicions were confirmed, then the only way out is to replace the kit or one candle.

5. There is no gasoline in the tank

You can diagnose the problem by looking at the fuel gauge. If it is faulty or there is a suspicion of its "inadequacy", then the presence of fuel can be determined by removing the fuel pump.

6. Contamination of the fuel filter, freezing of water in the system, pinching of the fuel line, failure of the fuel pump

All these malfunctions can be safely attributed to the same category, because they all have the same signs - the starter cranks the engine, but there is no smell of fuel from the exhaust pipe. If the car is carbureted, then the cause must be looked for in the float chamber. Most likely, no fuel is supplied to it. In the case of an injector, the presence of fuel in the rail is easier to check by pressing a special spool (installed in the end of the rail).

To fix the problem, it is necessary to thoroughly warm up the engine and pump the power system with a tire pump. After that, all the pipes of the system, hoses and the gas pump itself are changed.

7. Fuel pump creates too little pressure

This problem can be determined exclusively by special measurements (made directly at the outlet of the fuel pump). After that, the quality of the fuel pump filter is checked.

The solution is to clean the fuel pump filter, replace it (if repair is impossible) or install a new fuel pump.

8. Poor quality of contact in the circuit

Poor quality of contact in the circuit through which the fuel pump is powered or failure of its relay. The first thing to do to check is to make sure the quality of the "mass" on the car and measure the resistance with a multimeter. If the resistance level is really too high, then the only way out is to clean the contact groups, crimp the terminals well, or install a relay (if the old one is faulty).

9. Breakdown of nozzles or malfunction in the supply system

If there is a suspicion of a failure of these elements, it is necessary to check the winding resistance with a multimeter for the fact of an open or interturn short circuit. If the cause of the problem is a malfunction of the computer, then such a check can be carried out exclusively at a service station.

There are several ways to eliminate the decrease in engine power for this reason (depending on the depth of the problem) - install a new computer, clean all the nozzles, ensure high-quality contact in the electrical circuit, and so on.

10. Breakdown of DPKV

Breakage of DPKV - crankshaft position sensor or damage to its chain. In such a situation, the "Check engine" malfunction lamp comes on. The first thing to do is to inspect the integrity of the DKPV itself, to make sure that the gap between the gear ring and the sensor is normal (it should be about one millimeter). Normal sensor coil resistance is about 600-700 ohms.

To solve the problem, it is enough to restore normal contact in the electrical circuit and install a new sensor (if the old one turned out to be faulty).

11. DTOZH is out of order

Failed DTOZH - a sensor that controls the temperature of the coolant. The symptoms of the malfunction are as follows - the engine malfunction lamp comes on. If there is a break, then the electric fan of the system begins to rotate continuously. In addition, it is necessary to check the serviceability of the sensor itself.

If the engine power has dropped for this reason, then it is necessary to restore the quality of the contact in the electrical circuit and install a new sensor.

12. Failed TPS

The DPDZ is out of order - a sensor that controls the correct position of the throttle valve (or its chain). As in the previous cases, the "Check engine" lamp comes on here. If there is an open circuit in the DPDZ circuit, then the engine speed usually does not drop below one and a half thousand revolutions.

The solution to the problem is to clean the throttle assembly and restore the quality of the contact connection in the entire electrical circuit. If the sensor is defective and beyond repair, it must be replaced.

13. The DMRV is out of order

The DMRV is out of order - the sensor responsible for monitoring the mass fuel consumption. Here, the optimal action is to check the integrity of the mass air flow sensor or replace it with a serviceable device. If the failure of the mass air flow sensor is confirmed, then an attempt must be made to clean it, and if it is impossible to repair it, simply replace it.

14. Failure of the knock sensor

Damage to the knock sensor. With such a malfunction, the engine malfunction lamp on the instrument panel must light up. In addition, if the detonation DD fails, there is no detonation in any of the operating modes of the power unit and the engine power also decreases. With such a problem, the best option is to restore the integrity of the contact group in the electrical circuit and install a new sensor.

15. Breakage of the oxygen sensor

Breakage of the oxygen sensor or violation of its circuit. This malfunction is characterized by the "Check engine" lamp lighting up. In this case, the first thing to do is to check the integrity of the heating coil. First, the resistance is measured, and second, the voltage level at the output. Measurement can be done even without breaking the circuit - just pierce the insulation with needles.

To eliminate the malfunction, it is worth repairing the oxygen sensor, restoring the quality of the wiring and cleaning all the holes through which air is sucked in. In extreme cases, it is necessary to replace the oxygen sensor itself.

16. Depressurization of the exhaust system

It is easy to diagnose such a problem - it is enough to inspect the main elements while the engine is running at medium speeds. To solve the problem, it is necessary to replace the exhaust manifold gasket and stretch all the seals.

17. Failure of the ECU

Failure of the electronic control unit (ECU). Despite its reliability, the ECU can also break down (sometimes its software simply gets lost). To make sure that it is working properly (failure of the ECU), it is necessary to check the voltage on the unit itself (the normal parameter is about 12 Volts) or replace it with a known working unit. If the control unit is defective, it may need to be replaced. In some cases, it is sufficient to change only the wiring.

18. Violation of clearance adjustment in the valve drive

The compliance of the parameters can only be verified by checking with special probes. If the gaps are not correct (written in the manual), then adjustments must be made.

19. Deformation or breakage of valve springs

In this case, you will have to remove the cylinder head and measure the length of the springs under load and in a free state. If broken or deformed springs were found, then they need to be changed.

20. Camshaft cams are worn out

Here, a visual inspection will be enough (after removing the necessary elements) and replacing the camshaft, if necessary.

21. The valve timing is broken

In such cases, it is necessary to check the fact that the marks on the camshaft and crankshaft coincide. If there is an "imbalance", then it is enough to establish the correct position according to special marks.

22. Low level of compression in the cylinders

Low compression level in all or some of the cylinders. The reasons include probable valve damage or wear, breakage or sticking of the piston rings. To verify the suspicions or refute them, it is enough to take the necessary measurements. If the suspicion is confirmed, then it is necessary to repair the power unit - change rings, pistons or repair the cylinders.

The above is only a part of the malfunctions due to which the engine power drops. But in most cases, this is enough to diagnose the problem, fix it, and return the much-needed traction to your iron horse.

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

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

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

Read in this article

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

To begin with, on many cars with an injector, it raises the speed during warming up. This is necessary in order for the power unit to operate stably after a cold start.

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

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

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

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

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

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

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

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

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

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

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

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

Floating revs: reasons

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

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

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

Let's sum up

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

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

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

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

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

Read also

Why the engine can have increased idle speed. The main reasons for the high speed of the XX on the injection engine and engines with a carburetor.

During the operation of the car, drivers have to face various problems. One of the faults, which is quite widespread, is the constant maintenance of high revs by the engine. That is, even at idle, the engine speed does not drop. This problem can be observed in both injection and carburetor engines, but the reasons will be different. In the framework of this article, we will consider which malfunction is a symptom of this problem, and how you can get rid of it.

How to diagnose that idle speed is not falling

Even an inexperienced driver can easily notice that the idle speed of the car does not drop. This is easy to determine by ear, because, as you know, the lower the rpm, 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 time.

Depending on which engine is installed in the car, the idle speed may vary. On average, it is generally accepted that the engine is operating normally when idling is in the range of 650 to 950 rpm. If the revs are higher (unless otherwise stated in the technical passport for the car), then this can be called a deviation.

Please note: On most vehicles with injection engines, the Check Engine light on the dashboard comes on at high idle speeds.

What are the risks of high idle speed

The first thing a driver should remember is the high fuel consumption at high revs. Accordingly, if high revs are maintained at idle, this means that some 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 eliminated 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, it is necessary to consider why there may be a problem with high idle speed in such engines, since most of the problems overlap with injection engines. In the event of such a malfunction, you should pay attention to the following elements:

Most of the problems that lead to high idle speed in a carburetor engine are discussed above. Also, a common problem for carburetors and injectors cannot be ruled out - a jammed gas pedal.

Why the idle speed of the injection engine does not fall

Now let's look at the malfunctions that lead to increased idle speed in an injection engine. Unlike carburetor engines, where all the problems are of a mechanical nature, a malfunction in the injector may be associated, among other things, with improper operation of the electronics. The main reasons are as follows:

As you can see, there are a lot of problems due to which the idle speed does not decrease. If a similar malfunction has occurred, you should start looking for its cause as soon as possible in order to prevent even more serious problems.