Engine speed does not drop at idle: causes and consequences

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

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

Similar situations occur in almost everyone who has an injector and carburetor, diesel and gasoline internal combustion engines under the hood. However, the reasons for injectors and carburetors are different. Let's take a closer look at them.

How to diagnose that the idle speed does not drop

Even an inexperienced driver can easily notice that the car’s idle speed does not drop. This is easy to determine by ear, since, as is known, 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 what engine is installed in the car, the idle speed may vary. On average, an engine is considered to be operating normally when the idle speed is between 650 and 950 rpm. If the speed is higher (unless otherwise stated in the technical data sheet for the car), then this can be called a deviation.

Please note: On most cars with fuel-injected engines, the “Check Engine” light on the dashboard will come on at high idle speeds.

Replacing the Throttle Position Sensor on a VAZ 2110

Using a Phillips screwdriver, unscrew the two sensor mounting bolts, disconnect the block and remove the sensor.

If traces of rust or oxidation are found on the rod, which regulates the speed, it is necessary to clean it with penetrating lubricant.

Next, a new sensor is installed, the block is connected and the idle speed is checked.

What are the consequences of high idle speed?

The first thing the driver should remember is the high fuel consumption at high speeds. Accordingly, if high speeds remain at idle, this means that part of the fuel “flies into the pipe.” Moreover, this problem directly affects the life 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.

How to avoid the problem

If all the parts and components of the car are in order, then the problem for cars equipped with fuel injection may lie in the ECU firmware. It is the control unit that regulates engine speed and the composition of the air-fuel mixture entering the cylinders. To avoid the problem of maintaining high speeds in the future after releasing the gas or warming up the engine, you can reflash the electronic control unit.

Another reason that the speed is maintained while driving may be the mat sticking behind the gas pedal. In this case, the accelerator pedal does not go down completely, which leads to excessive enrichment of the fuel-air mixture. To prevent the problem, you just need to adjust the rug.

Why does the idle speed of a carburetor engine not drop?

At the moment, carburetor engines are practically not used in modern cars. However, it is necessary to consider why high idle speed may be a problem in such engines, since most of the problems overlap with fuel-injected engines. If such a malfunction occurs, you should pay attention to the following elements:

Adjusting the idle system. It is possible that it is adjusted incorrectly, which is possible after cleaning or repairing the carburetor. If the carburetor has recently been adjusted, the air/fuel ratio may have been set incorrectly, leading to the high idle problem;
Throttle valve malfunction.
If the throttle valve does not close properly, the problem in question will also occur. Most often, problematic operation of the throttle valve is associated with the presence of carbon deposits on it. Accordingly, it is recommended to clean the damper. But it is possible that the situation is more unpleasant, for example, a crack or chip on the throttle valve. In this case, it will need to be replaced, which is not possible on all carburetor engines;
Needle valve position. If such a malfunction occurs, fuel will flow into the chamber in incorrect doses. At the same time, depending on the location in which the occurrence occurred, idle speed may disappear or increase;
Burnt out cylinder head gasket.
If burnout occurs, the gasket will need to be replaced. The easiest way to check the normal operation of the gasket is with the engine running. To do this, open the hood and open the radiator cap. If white smoke starts pouring out, the problem is definitely in the gasket and it needs to be changed;
Open suction. To verify this malfunction, you need to check how the damper in the primary chamber works. If a problem is found during the inspection, check how the choke works. It is worth noting that most often, to eliminate the malfunction, it is enough to simply lubricate the damper drive and cable.

Most of the problems that lead to high idle speed in a carburetor engine are discussed above. We also cannot exclude a common problem for carburetors and injectors - jamming of the gas pedal.

Let's sum it up

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

If the problem is not on the surface (the throttle cable has become sour, after washing or dry cleaning, the carpet in the cabin is not installed correctly, which presses the gas pedal, etc.), then it is better to take the car to a service center.

The most complex situation is when the design of the power system 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.

Why does the idle speed of an injection engine not drop?

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

Incorrect operation or failure of the coolant temperature control sensor.
If this sensor is faulty, the car engine will constantly work in warm-up mode, which is why it will stop slowing down. Since no information is received from the sensor (or it is received, but incorrectly), the control unit believes that the engine is not yet warm enough and tries to heat it up. This problem is extremely serious, and it can lead to overheating of the engine, as well as the need for major repairs. To identify this malfunction, you must use a diagnostic scanner;
Incorrect operation or failure of the idle speed sensor (mass air flow). As with any other sensors, diagnosing the car with a scanner will help determine the malfunction. If the scanner indicates that the sensor is faulty, you must first check it with a multimeter to eliminate the possibility of a broken wiring;
Incorrect operation or failure of the throttle position sensor. Another sensor that plays a key role in the operation of an injection engine. If the sensor provides information to the electronic control unit that the throttle valve is open, the number of revolutions will increase. The problem may be either a jammed part or a sensor failure;
Problems with the damper return spring. If the return spring is too stretched or has slipped completely, it may be causing the problem in question. In such a situation, you will need to put it in place or replace it, depending on the problem and the condition of the spring;
The throttle cable is stuck. This malfunction is typical for very old cars. If this occurs, you will need to replace the cable or lubricate it, depending on the situation;
Damage to the injector seals. An extremely difficult malfunction to diagnose, the presence of which should be checked last. If the gaskets are damaged, additional air will begin to flow into the combustion chambers, which will lead to an increase in speed.

As you can see, there are quite a lot of problems due to which the idle speed does not decrease. If such a malfunction occurs, you should begin to find its cause as quickly as possible in order to prevent even more serious problems.

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Injector system

If your car has an injection system, there may be many more reasons for high idle speeds. Here, both mechanical elements and electronic devices responsible for adjusting the idle speed can fail.

The main injector malfunctions include:

Incorrect operation of the temperature sensor installed in the cooling system. Incorrectly received data from this device causes the electronics to recognize the engine as cold and work to warm it up, thereby maintaining high speeds necessary to reach operating temperature. Overheating can often occur, which leads to more serious damage, including major engine repairs. The same effect is possible if the idle speed control is not operating correctly.
The throttle control cable may become stuck. The higher the mileage of the car, the higher the risk of encountering a similar problem.
The electronic XX operation sensor often malfunctions, then the speed will either increase or disappear altogether.
The spring that brings the throttle valve to its original closed position is not functioning properly, is jumping off, or is being stretched too far.
Too much air enters the fuel combustion chamber due to poor quality or leaky gaskets. It is necessary to carefully check the seals of the manifold and injectors.
And the simplest reason is usually the incorrect placement of the mat after a visit to a car wash or dry cleaning of the interior. It is often inaccurately placed under the accelerator pedal, which leads to the appearance of improper engine operation.

If the car is oversaturated with various electronics and all the work is based on the correct functioning of the sensors, one of them may well become a problem. It will supply incorrect data to the computer, and as a result, the speed will not drop. You will most likely not be able to detect the problem on your own.

It is necessary to contact a car service for computer diagnostics. The task is best handled by specialists working at a service center that specializes in repairing a specific brand of car. If the diagnosis is carried out on time, then it is quite possible to get away with simply replacing the sensor.

You shouldn’t delay repairs, because a supersaturated mixture has a bad effect on engine performance and significantly shortens its service life.

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Comments 24

I have the same problem on my 15x, what did I do?

I pulled all the bolts on the receiver and manifold, changed the IAC and TPS, everything became better, and it turns out that it shouldn’t slow down very quickly.

after high revs you squeeze the clutch the revs slowly drop, this rarely happens to me, but on the Nexia the revs often didn’t drop, kept it at 2000, sold it without understanding it, now the 15x has a similar situation, what a curse!

check light is not on? if the check light is on, then the mass air flow sensor may not be working, and if the mass air flow sensor is not working, then below 1.5 thousand revolutions and it will come off... and the IAC may jam, it’s better to change the IAC and the air flow sensor, as they together cost 500 rubles or less.

I’ll take the advice into account, I also thought - I’ve been wanting to change them for a long time, I don’t have any money yet, but tomorrow I’ll register my basin on the website, come in! and thank you, I saw a lot of interesting things!

You're welcome) we'll definitely come in) how to say - come in too if anything happens)))

MAF may be dying, diagnostics, or measure the voltage yourself

no, it’s not a DMRV, I checked it yesterday. Everything is okay! and so the DMRV is new, I bought it a month ago)

then look for an air leak in the intake

ok) thanks for the advice)

There was such a problem, we searched for a long time, with the help of a steam installation we found the cause - air leaks through the nozzle rings! Symptoms - the speed was set by itself, when the gas was released it stopped at any level, the response to the gas pedal was weak))) Something like this)

thanks for the advice) we'll take a look)

The opening of the damper should be possible to see on the BC, he takes it from the DPDZ. look rxxx first. he usually dies more often

Yes, I checked the opening and closing of the throttle using b.c. Thanks for the advice! I'll change the IAC, and for one thing I'll buy the TPS.

It will be useful on the farm if anything) although of all the sensors in six years, only the DPRV has died.

a clear sign of problems with the fuel pump and compressor. The culprit could have been a mixture of gasoline (perhaps it was leaded). although if it doesn’t help, then you need to look further at the fuel distributor (injector). spark plugs and wires hardly play any role here. Well, at least you can dry the candles just in case. and I had the same problem. I replaced the fuel pump and everything went away. good luck with cars and smooth roads.

The main causes of the third stage of hypertension

With arterial hypertension (AH) grade 3, blood pressure increases to 180/110 mmHg, and sometimes exceeds them. In this situation, it is impossible not to use medical help, otherwise more serious disturbances in the functioning of the cardiovascular system are possible.

Most often, this pathology develops in older people. It happens that the upper numbers on the tonometer exceed 180 mmHg, while the lower ones drop to normal. This can significantly complicate treatment. This pathology may be accompanied by disturbances in the functioning of vital organs, which corresponds to risk grade 3 or 4.

The development of a disease such as stage 3 hypertension, risk 3 or 4, is caused by various factors influencing from the outside and from the inside.

Causes of high blood pressure:

kidney pathologies, disruptions in the functioning of the heart and blood vessels;
obesity, diabetes mellitus, metabolic disorders;
poor nutrition;
age restrictions, gender;
chronic fatigue, stress, psycho-emotional overload;
alcohol abuse, smoking addiction;
sedentary lifestyle;
hereditary factor.

Some of these reasons can be influenced, others should simply be taken into account. In this case, therapy will be easier to carry out and the risk of more serious complications will be reduced.

Interruptions in the operation of carburetor and diesel engines

Why do engine speeds fluctuate in carburetor cars? Unstable activity may be caused by the following reasons:

Failure of adjustments in idle modes.
Failure of the carburetor engine solenoid valve.
Excessive accumulation of combustion products in the nozzle.

Diesel engines have jumps and drops in the instrument readings during intermediate modes and when idling.

In these cases, they say that the diesel engine speed is floating. The cause is rust formed on the impeller of the high pressure fuel pump. Water contained in diesel fuel causes corrosion.

Consequences of unstable motor activity

All of the above reasons for engines running intermittently cause a number of negative consequences:

increased consumption of gasoline or diesel fuel;
environmental pollution with exhaust gases containing an increased percentage of harmful gases;
increased wear of components and parts of the power unit.