Why does the car twitch when driving? The reasons why the machine jerks at idle, when shifting gears, when braking and at low speed

Drivers sometimes notice that when the automatic transmission is switched the machine jerks unexpectedly, the same happens on the descents, at the ascent and so on. What is the reason for this behavior of the vehicle? There are a lot of reasons, but under any conditions the twitching machine can become an involuntary cause of the emergency situation. Below, we will outline the most common situations in which you can face this problem.

Prevention is better than repair!

But first answer the question: "How to determine that the machine is twitching on gas?" It would seem a strange question. But if you already clearly feel shaking in the car, then the problem has reached its apogee and has become too obvious. And, as you know, any problem is easier to prevent than to eliminate. Therefore, try to pay attention to changes in the movement of your vehicle as early as possible. And then there is a hitch - few drivers will be able to notice this.

At once it is necessary to say that it is wrong to check the machine for presence / absence of pulling movements at idle (except in rare cases), this can only be done while driving. Selecting an even safe way, alternately switch gears. At each of them, press the accelerator pedal sharply. The car should respond only to your pressing, even the easiest. If the car jerks without your desire or feel jolts when lifting, then you need to look for the causes of this problem.

When overclocking, the machine jerks ...

You gain momentum, and the car starts to pull, its course ceases to be smooth? The reason lies in the unstable flow of fuel into the float chamber: it disappears from there faster than it does. It supplies fuel to the gasoline pump, so it may be in its malfunction. How to "cure" it? To do this, remove the cover of the gasoline pump and carefully inspect the hole where the valve should be. Often, the O-ring is near, and not in place, or none at all. Because of the depressurization and there are interruptions in the injection of fuel, and, consequently, the machine jerks on the move. Repair in this case is to replace the valve and restore the integrity of the system. You can do it yourself, if you have a new sealing ring of a suitable diameter and tool. This work will take about half an hour, and the professional will manage in 5 minutes.

Jerks when driving at low speed

If the machine jerks at low speed, then check the operation of the injectors. Carefully inspect and harness - if it lies directly on the fuel pipe, it can be rubbed off. This will lead to the fact that when tapping the wires of the tube, the wiring closes and the injectors are turned off. When replacing the wiring, the problem should disappear.

What if the car jerks when you press the gas?

If the machine jerks when pressing the gas, then in order to eliminate this defect, it is necessary to understand what is the reason. For example, the reason that the machine jerks on the gas may be a vacuum ignition timing regulator. This detail, as a rule, is located on the toggle switch. The characteristic twitching is manifested most often if the regulator is broken, and here the replacement of the carburettor is meaningless. How does the vacuum cleaner work? The rate of combustion of fuel is always constant, and the engine speed increases, so we need to increase the rate of ignition of the fuel mixture during the movement. With a revolution between 1500 and 2000, the centrifugal regulator in the car does not work, when moving at high speeds this task is assumed by the vacuum ignition angle regulator. When the throttle is open, a rarefaction occurs in the diaphragm. This pulls the bearing behind it, and therefore increases the lead angle. Check the operation of the hose is simple enough. Cover one of its ends with a tongue or a finger - the hose should slightly "suck" this part of the body and stay hanging, since there is a vacuum inside it. And getting there the air leads just to the fact that during the acceleration the machine jerks.

The next culprit in the appearance of twitching during driving is the accelerator pump sprayer (drivers often call it a "teapot", "spout" or "samovar"). To see this detail and evaluate the efficiency of its operation, you will have to remove two removable diffusers and, by clicking on the lever, see how the "spout" works in each of the cameras. If even in one of them there is a failure, then this is the reason for an unpleasant situation, in which the machine stalls and jerks. Repair is as follows: remove the sprayer, clamp its lower part with pliers and pull out the ball. Then, clean the remaining part, blow it and collect the part back. Avoid deformation, so the air must fall strictly into the diffuser and into the manifold, and not against the wall. After you place the spray gun in its original place, again check its operation - the working part gives a long straight stream. Removable diffuser should be installed correctly, that is, close to the body of the carburetor. If there is space left at the junction, an undesirable rarefaction may occur.

Machine jerks when driving: diaphragm failure

Breaking the diaphragm of the accelerator pump is a very rarely diagnosed problem. It is expressed by the fact that only the spring remains on the diaphragm, and there is no button that closes it. In this case, you can think of her homemade analog, but often in the car repair shops do not check the presence of this small detail, and resort to an expensive replacement of the carburetor.

Check fuel filters

The lack of fuel, which leads to jolts during the movement of the machine, can be caused by contamination of fuel filters. Their number varies depending on the type of engine. For example, in diesel engines there are two: for preliminary and fine cleaning of fuel. Most often the latter is the reason that the machine jerks when driving. To determine in what state the first filter on the fuel receiver is located, you need to detach the rubber hose from it and blow off the mesh. While performing this manipulation, do not forget about one obligatory condition: the fuel tank cap must be removed. The procedure should be repeated after a few days, not only cleaning the fuel filters, but adding to this the flushing of the fuel tank. This will help to avoid re-clogging the grid and prolong the life of the filter. If the machine still jerks when starting, check the fine filter. The machines of Japanese brands, it is disposable, that is, it does not need to be cleaned, but just need to put a new one. In order to replace the fuel in the filter with confidence, fill it with the part before starting the engine. To do this, one hose coming from the fuel tank is replaced with a transparent tube and the mouth is pumped liquid into the filter. After this, you can again put the standard hose and press the hand pump several times . Only after this, you can start the engine and evaluate its performance. Thus, you can quickly fill the filter, while injecting fuel only with a hand pump will take much longer. To restore the old fuel filter, having cleaned it from rust and pollution, too it is possible, but it is actual for cars not the Japanese manufacture. To remove the filter, remove the attachment of the booster pump, unscrew the lower plastic plug and the part from the part. Do not be afraid to damage its lower part, clamping the part with a vice: the filtering component is higher in it, and the lower third is a settling tank, all the impurities accumulate in it. Clean the filter will help us hot kerosene. To do this, pour the clean kerosene into any metal container (bowl, pan, etc.), add a small amount of water (about a tablespoon) to it and put it on the fire. Naturally, the evaporation of kerosene with flavors can not be called, so these manipulations are recommended to be carried out in a well-ventilated room, taking care of personal protective equipment well in advance. Watching the water on the bottom of the pan, you can trace the heating of kerosene. When water boils, you can lower the filter into the tank, after removing all the plastic parts from it. While holding the filter with tweezers, rinse it in a heated liquid. If necessary, you can cool the kerosene after boiling water, and then repeat the entire procedure anew. As it has already become clear, the water plays only the role of a temperature indicator. What is it for? In this way, we evaporate the water from the filter and clean it of rust.

Boiling kerosene is able to clean the part and from the paraffin deposits that settle on the grid, if the car uses fuel with their high content. Kerosene dissolves the paraffins, and the filter after this cleaning will be able to serve you for about ten thousand kilometers (of course, if you do not fill the tank with low-quality fuel). If you are afraid of tearing the filter element, it is not recommended to blow it with compressed air. Some drivers deftly modify the fine filter system, which allows them to use domestic filtration models. Modernization consists in the fact that the basic import filter is complemented by a glass, which can be disassembled. Such processing is actual if you are in places where it is impossible to repair a vehicle or replace a part with a new one. But here you can also face difficulties. Models of Japanese replaceable filters often have double walls with filler between them, so welding work can become not only labor intensive, but also fire dangerous, since the filler is combustible. Also, when talking about fine filters, you need to keep in mind that if the part gets dirty, the engine may run intermittently, but it does not jerk the machine. Especially it becomes noticeable when driving on the rise - the engine is constantly deaf, sneezes. The fact that the engine has lost power can be determined by stopping at the roadside and starting with a manual pump to fill the fuel filter. Normally, the button should return to its original position, but when you press the gas, it will keep pressing the pressure from the feed pump from the injection pump. If, on braking, the machine jerks, the fault may be a malfunction of the clutch discs, or you need to look for the cause in the automatic transmission.

Diesel engines are equipped with the same fine filtration systems, so it is easier to select parts for them - they do not depend on the type of engine or brand of the machine.

In some cases, the fuel system can be equipped with another screen filter. It is located at the inlet of a high-pressure fuel pump, for example, it is on all Nissan cars. To see and remove it, remove the bolt securing the pipeline to the pump and see the plastic housing in which this part is mounted. But in the cars "Toyota" it will be installed a little differently: above it will be a solenoid valve for cutting fuel (involved in engine muffling). By the way, if you own a car with a diesel engine and noticed that when idling its revolutions "float" (then increase, then fall, then return to normal), check the cleanliness of the filters - often the presence of contamination in them leads to this problem.

If we talk about the carburetor engine ...

And what if you have a carburetor engine? At the beginning of the article, we have already mentioned several situations in which the machine jerks on the run due to the fault of the carburettor's incorrect operation. But the reason may be filters and fine fuel cleaning. The simplest thing in this case, of course, is to replace them, but not always in road conditions it can be done. If the problem is found on the trip and visit the car repair shop is not possible, the first thing that can help is washing the filter with the reverse course of gasoline, as on Japanese cars it is most often put on a direct rail to the gasoline pump. This will help you get at least to the nearest car service or garage. Some drivers resort to piercing this filter, but this advice is not only wrong, but even harmful. Vorsels that separate in this case undoubtedly fall into the carburetor, which very quickly removes this part of the system, thus, the replacement of this costly detail will be required. If you do not have at your fingertips a "native" filter, for example, from Toyota, you can use its analogue from another car with a carburetor engine, in which case such components are interchangeable and differ from each other at times only in diameter.

Some brands of cars (for example, Honda) have a non-standard arrangement of a gasoline pump, hence, it will be difficult to find a filter system from the first. But if your car jerks when driving and you want to fix it, here are some tips. Most often an electric gasoline pump will be next to the gas tank, and filters - in front of it. Do not forget that in engines of this type there is a third filter element. It is located in the carburetor itself, in the place where gasoline comes in. To clean or at least inspect this part, it is often necessary to disassemble the carburetor, but in some cars (for example, in Nissan), access to the filter grid is much easier. The whole process of work is as follows:

1. Unscrew the fixing bolt of the inlet pipe.
2. Remove the nozzle.
3. Get the filtering mesh right under it and clean it.
4. Put the filter back in place and attach the pipe.

If this is not possible, you will have to perform the following series of manipulations:

1. Remove the top cover of the carburetor and turn it over.
2. Pull the axis of the float.
3. Remove the float and the corner stopper.
4. Next, go to the needle valve and unscrew its saddle (for this purpose you will need a small wrench or a conventional flat-blade screwdriver).
5. Remove the saddle, turn it over, clean the filter mesh on its back side.

Sometimes a complete removal of the saddle is not required, it is enough to blow the formed hole with a compressed air jet after the needle is removed. This simple manipulation will help to clean the filter qualitatively. But the first filtration system that passes the fuel in the carburetor engines is the strainer on the intake tube in the gas tank. Its cleaning is similar to the cleaning of filters in diesel engines, which we already mentioned above.

Now we turn to the problems of gasoline engines, which can also lead to the fact that you feel the car twitching. As already clear, in detail we will disassemble its filtration systems. At once it is necessary to tell, that the quantity of filters here varies depending on an arrangement of the fuel pump. If it is located inside the gas tank, the filtration system will consist of a receiving grid, a fine filter and screen filters in front of the injectors. If the pump is pulled out, then in addition to the ones already listed it will be possible to find the fourth one - a mesh cone-shaped filter located in the pipeline in front of the gasoline tank. If you want to pull it out and clean it, first remove the hose for the inlet pipe of the gasoline pump, then use the tweezers to carefully remove the cone. But do not forget that if the above does not help, and the machine jerks when driving, the injector in such cases should also be checked for serviceability.

Twitching the car? Check the spark!

Defective work of the sparking system often gives itself out by the fact that the machine starts to jerk when it comes down from a hill or on an even section of the road. For example, this problem was often encountered in Nissan cars, because their engine CA-18 was equipped with a contactless trambler. In the case of this part there is a commutator, malfunctions in its operation and lead to such specific movement of the car. Correct the twitching can only be replaced with accessories.

The culprit - the control unit

Another possible reason why the machine jerks when changing gears is the faulty operation of the carburettor control unit (in the English-speaking version, its name sounds like "emission control"). In this case, the nature of the shocks will be random. Calculate the real reason for their appearance is quite difficult, because they are not permanent, but only sometimes appear when driving. If you suspect that something is wrong with the car, we recommend that you contact the car service center, make a diagnosis of all the systems on the stand. Also on the lift it is easy to see that the machine twitches at idle. "Movement" of the car with light wheels usually helps not only to determine why the car pushes, but also to track the "swimming" of the turns, which we mentioned earlier. Often these two problems are connected, and only the qualitative work of auto mechanics helps to determine the cause. And the culprit here is the control unit (EPI). Unfortunately, in this case, in order to discover the cause, it is necessary to create certain conditions for the operation of the car (giving a specific speed, a certain load), and it is unrealistic to fulfill all these conditions while driving. Due to traffic on the road, the engine's operation is constantly changing, and there is a twitching effect.

Conclusion

So, we have described almost all the options for why the car jerks when driving. As you can see, there are quite a lot of reasons for this movement, and if you are not an expert in the automotive "stuffing", you are unlikely to be able to correct the situation. But there are moments when professional equipment can not be dispensed with, for example, it concerns diagnostics at idle. In any case, if you notice jerks or twitches while riding, do not leave it unattended and always visit the car wash. Pay attention to the reputation of the workshop, read the reviews about it, visit the site, so as not to fall for the bait of scammers. Many novice drivers cleaning filters, for example, can fly into a lot of money, so ask about the cost of services in advance. It is also useful to interview acquaintances. But remember: the operation of a car that twitches is not only uncomfortable, but also dangerous, as it is fraught with an accident. Be careful and good luck on the roads!