Why does the car idle at a high speed when it starts and then drops down after a while?

Because the engine needs to be coordinated by itself.

When the engine is usually working, the environment is in a relatively high temperature, so if you look at it according to the principle of thermal expansion and cold contraction, then the engine will be in a state of contraction in a relatively cold environment. Therefore, when the car is hot and cool, there is a difference between each moving part. In the process of making the engine, there will also be some expansion space to ensure that the engine can work normally.

And we just ignite when the engine temperature rises, and then rises to the normal temperature, at this time the gap between the components will reach the best, so the high speed is actually because the engine at this time is running crazy, the purpose of this operation, in fact, is to heat up as soon as possible, after reaching the best state, you can also reduce the loss of the engine.

There are gaps between engines, and if the gap between your engine parts is too large and the gap is not well sealed, it will increase wear. If your engine computer thinks the engine is working at a low temperature, it will automatically increase the air intake and fuel injection. This will get your engine hot as quickly as possible.

So at this time, the speed will increase, and the process is actually quite fast, generally in about a minute.

It can be seen that hot cars are still necessary, and whether it is summer or winter, hot cars are a must. However, it is important to remember that the longer the car is hot, the better, but as long as your engine reaches a steady speed, then we can drive at this time. Don't heat up the car for too long, because if it takes too long, it will cause more damage to the engine.

It is normal for the idle speed to be high at startup. Cars need high speeds to get the engine to normal working conditions as soon as possible, and a thick mixture is required.

In fact, this is not a fault, there will be in every car, this is actually a kind of engine protection measures.

Because the high idle speed is a facility for the vehicle to protect itself.

Because idling is used to cushion the vehicle and protect the vehicle.

Because the car has an automatic protection function, it will automatically adjust.

The engine will have this protection, normal.

Because the engine will automatically coordinate, normal phenomenon.

This is a measure for the car to protect itself, and there is nothing wrong with it.

Because it's just a protective measure for the engine.

The reason why the car idles at a high speed when starting and only drops to normal values for a while.

Why does the idle speed of the car be high when it is first started, and it will drop after a while? If you understand this principle, you will understand!

Just starting the engine with high speed, to solve this problem, you need to understand the principle of engine cold starting. This is mainly because the engine is in a cold state, the water temperature in the engine is relatively low, the engine control computer in order to make the water temperature reach the normal working temperature faster, it will control the amount of fuel injection, for example, the lower the temperature, then the more oil the injector will spray, which is equivalent to a thickening effect on the injector, so this is a normal phenomenon, when the engine of some cars starts, the moment of ignition can reach more than 2000 rpm, and the sound is also very loud, which is also normal.

1.When the car starts, it is in a cold state, and the idle motor of the car will automatically increase the air intake. It makes the gas inside the engine cylinder increase instantaneously. So the idle speed is much faster.

2.And when the engine temperature is low, it will also transmit this information to the driving computer system, which is what we call ECU, at this time, ECU will increase the amount of fuel injection, the purpose is to make the engine do not turn off at high speed. Only when the water temperature reaches the normal operating temperature will a command be issued to allow the idle motor to reduce the amount of air entering.

Then it will automatically descend and enter the normal working state.

3.But if your car is in a minute or two, the idle speed has not been reduced, then you should pay attention, at this time there may be a fault in the engine, if you don't understand, hurry to the auto repair shop for inspection and repair. Because it is always at high speed, it will damage the car.

In particular, engine-related parts wear out, and fuel consumption is still high. Waste of money. Over time, it may lead to the scrapping of the engine.

The engine is cool and the ambient temperature is low.

According to your description, this situation is normal, don't worry.

The idle state refers to the working condition of the engine when it is idling, that is, when the engine is running, the accelerator pedal is completely relaxed, and the engine is in the idle state. The speed at which the engine is idling is called idle speed, which is the minimum speed at which the engine can maintain normal operation without external output. Engines with good working performance generally have an idle speed of 550-800 rpm.

Unstable idle speed is in the idle state, the speed fluctuates high and low and changes greatly, which is the most common fault of the engine, and the main common reasons are:

1) The idle switch is not closed.

Diagnosis method: Turn on the air conditioner and turn on the steering wheel when idling, and the engine speed does not rise, which can prove to be this fault.

Exclusion: Adjustments, repairs, or replacements of throttle position sensors.

2) Idle control valve (ISC) failure.

Diagnostic method: Check the actuation sound of the idle control valve, if there is no actuation sound, the idle control valve is faulty.

Troubleshooting: Clean or change the idle control valve, and use a special decoder to set the idle speed basically.

3) Air leakage in the air intake line.

Diagnostic Method: If you hear a snorting sound of a leak in the intake pipe, it is evidence of a leak in the air intake system.

Troubleshooting: Find leaks, reseal or replace phase parts.

4) Injector dripping or clogging.

Diagnostic method: Use a stethoscope to check whether the injector makes a "click" actuation sound or measure the fuel injection volume of the injector, if the injector does not make a sound or the fuel injection volume exceeds the standard, the injector is faulty.

Troubleshooting: Clean the injectors, check the amount of fuel injected into each injector and confirm that there is no clogging or dripping.

5) Exhaust system blockage.

Diagnostic method: Use a vacuum gauge to detect the px, if the px is low and the acceleration is often accompanied by the phenomenon of stuffiness, it can be determined that this fault is the fault.

Troubleshooting: Replace the three-way catalytic converter.

In addition to the above fault causes, there are many faults that can also cause idle abnormalities, including: ECU failure; main oxygen sensor circuit; EFI main relay circuit; Standby power circuits; cold-start injector circuitry; Variable resistor resistance for gas mixture; fuel quality; Vacuum leakage in the inlet pipe; clogged air filter; Poor cylinder compression, etc.

It is estimated that there may be abnormal air intake, and it can be detected whether there is air leakage. How much do you idle when you first start?

Unless you turn it off, stop the fuel injection.

Idle and 2000 rpm or more injectors, 2000 rpm or more fuel cut-off control, fuel injection, then repeat until the speed drops.

This is a normal phenomenon, because the car engine, in the process of cold driving, the temperature is not high enough, and the lubrication is not good enough. Therefore, the signal sent by the engine sensor to the ECU can only be used as a reference signal, and the engine speed will increase accordingly, when the engine temperature reaches the standard temperature, the signal sent by the sensor to the ECU is a real signal, then the ECU will reduce the speed according to this signal and hit a standard idle speed. Generally about 750-850 rpm.

The rotational speed drops suddenly, then returns to normal.

Follow-up, is it the speed that goes up and down when the car is hot and doesn't accelerate?

In general, a high idle speed for a cold start is not a fault. Because the high speed of the engine after starting is intentionally controlled by the engine computer, its main purpose is to make the water temperature, oil temperature and three-way catalytic converter quickly reach the optimal working temperature, reduce the wear of the engine transmission, improve combustion efficiency and improve emissions.

All cars have a high idle speed process when starting cold, and the lower the temperature, the longer the high idle speed will be maintained. After ignition, the engine idle speed is generally between 1300-1500 rpm, and the sound of the engine is also very loud, as the water temperature gradually increases, the idle speed gradually decreases, and finally drops to the normal idle speed of about 800 rpm.

In winter, the atomization conditions of gasoline are poor, especially the carburetor vehicle, which is generally not easy to start, even after starting, it cannot be transferred to normal working condition immediately.

Therefore, when carrying out winter maintenance, it is necessary to clean and dredge each oil passage and airway, and check the working condition of the throttle valve, choke valve, accelerator pump and vacuum pump, which should be adjusted to the best state. At the same time, it is also necessary to appropriately adjust the fuel supply concentration of the idle speed to ensure the normal operation of the idle speed in severe cold.

The circuit is mainly to check the platinum gap of the distributor and the electrode gap of the spark plug. The platinum contacts of the distributor should be clean and non-ablative, the contact surface should be more than 70%, and the gap should be between millimeters.

For models using electronic ignition, the spark plug gap is generally between millimeters, and the spark plug gap is too large, and the engine is not easy to start when the car is cold; If the clearance is too small, the engine power output will be reduced, fuel consumption will increase, and exhaust emissions will exceed the standard.

The reason why the idle speed cannot be lowered after the cold start is caused by the failure of the idle control valve of the car. The workaround is:

If the idle control valve of the car is faulty, you need to go to the 4S shop or repair shop of the car in time to repair or replace the idle control valve of the car to solve the abnormal idle speed. Generally speaking, because the car needs to enter the normal working environment as soon as possible after the car starts, the engine computer will automatically inject more fuel when the car is cold, and quickly increase the water temperature of the engine by burning more fuel than the normal idle speed, so that the engine can quickly enter the appropriate temperature. Additional Information:

The introduction of car idle speed is as follows: the power of the engine is the combustion of fuel, and the fuel is completed by the fuel injection system, ignition system, and mechanical structure, so the instability of the idle speed is likely to be due to the abnormality of these systems. For example, air intake system leakage, fuel pressure is too low, air filter is clogged, injector atomization leakage, improper idle speed adjustment, spark plug work poorly, air flow meter failure, etc.

Under normal circumstances, the amount of air intake into the engine must be strictly limited, and if there is an abnormality in the air intake system, throttle, air flow meter, idle control valve, or leakage, it may cause the engine to idle unstable. Reference**: Phoenix.com - Car Owner:

You know the original. Questions. The cold car can not be idled, and the temperature is good after driving for a period of time, and the fuel consumption has been high recently.

You look to see if the center console is in snow mode or if a c is turned on.

The reason why the car idles at a high speed when starting and only drops to normal values for a while.

1) It is normal for the idle speed to be high when starting. Cars need high speeds to get the engine to reach normal working conditions as soon as possible, and they need a thicker mixture, so the air intake and fuel injection will increase, resulting in high speeds.

In order to save fuel and reduce wear and tear when starting, there is generally a cold car fast idle or water temperature sensor, (water temperature sensor, as the name suggests, is an electronic component that detects water temperature, provides signals to the ECU, and ensures that the engine controls the amount of fuel injected when starting or running.) Further, the ECU changes the amount of fuel injected each time according to the signal provided by the water temperature sensor to meet the different needs of the engine for fuel supply under various operating conditions).

The colder the weather, the lower the water temperature (higher than the normal working temperature of the engine, generally about 85-110 degrees), that is, the greater the temperature difference with the normal engine operation, the computer will control the cold car to idle, that is, the higher the engine speed when it is just started. Under normal circumstances, according to the different water temperatures, the idle speed of the engine will slowly decrease from more than 2000 until the engine reaches the normal working temperature and reaches the standard idle speed of about 800 rpm.

2) High rotational speed is generally the cause of excessive carbon deposit. Timely cleaning of the throttle and idle motor can usually solve the problem.

Reasons for high car idling:

1. The idle switch is not closed;

2. The idle control valve is faulty;

3. Air intake pipe leakage;

4. The gas distribution phase is wrong;

5. The injector is dripping or clogged;

6. The exhaust system is blocked;

7. The EGR valve is opened when idling.

After the car starts, after the idle speed is normal, the idle speed will be high, which is mainly a problem with the computer, because the driving computer will make the idle speed increase after you just start the car, so as to ensure that the lubricating oil quickly reaches all parts of the engine

When the vehicle is just on the car, the idle device is working, after acceleration, the throttle opens, there will be a large amount of air into the engine, if the throttle is not properly returned, it will cause the idle speed to be too high. So this situation is very simple to deal with, in fact, it is enough to clean the throttle and idle valve thoroughly. Then do a good job of matching the throttle.

The idle speed of the car is too high when it is driving normally, which is actually an illusion, because it is not the control speed of the engine, but the speed of the vehicle when driving the engine in reverse, such as when coasting, when going downhill, even if the accelerator is lost, the vehicle is still moving forward at a certain speed, which is the speed of the vehicle in turn drives the engine to increase the speed, giving people a feeling that the engine is idling high.