Why car jerks when driving? Reasons why car jerks at idle, when shifting, braking and at low speed

Drivers are sometimes notice that when you switch automatic transmission car jerks suddenly, and on the descents, while ascents, and so on. With what is the behaviour of the vehicle? The reasons are many, but under all conditions the twitching machine can become the unwitting cause of an emergency. Below we outline the most common situations in which you may encounter this problem.

Prevention is better than repair!

But first answer the question: "How to determine that the car jerks on throttle?" It would seem a strange question. But if you already clearly feel the shaking in the car, so the problem reached its peak and became too obvious. As you know, any problem is easier to prevent than to eliminate. So try to pay attention to changes in the movement of their vehicle as early as possible. And then there is the hitch – a few drivers will be able to see it. 

Immediately I must say that to check the machine on the presence/absence of jerking movements at idle is wrong (except in rare cases), this can only be done while driving. Selecting smooth safe stretch of road alternately shift gears. Each of them sharply step on the gas. The machine should respond only to your touch, even the lightest. If the car jerks without your desire or felt the tremors while lifting, then you need to look for the causes of this problem.

When accelerating the car jerks…

You are gaining momentum, and the car begins to pull, its course ceases to be smooth? The reason lies in the unstable receipt of fuel in the float chamber: it fades out faster than it comes. Delivers there fuel pump, so it can be his fault. As his “cure”? To do this, remove the cover of the fuel pump and carefully inspect the hole where there should be a valve. It often happens that the o-ring is near, and not in the right place, or non-existent. From–decompression and there are shortages of fuel injection, and therefore, the machine jerks on the go. Repair in this case is to replace the valve and restoring the integrity of the system. It can be carried independently if you have a new o-ring of suitable diameter and tool. This new job will take maybe half an hour, and a professional will handle it for 5 minutes.

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Jerks when driving at low speed

If the car jerks at low speed, you should test the injectors. Inspect and harness – if it lies directly on the fuel tube, it can peretiraetsya. This will cause interference with the wires of the tube will occur at a circuit wiring and disconnect injection nozzles. When replacing the wiring, the problem should disappear.

What to do if when you press the gas the car jerks?

If you press the gas the car jerks, in order to eliminate this defect, you should understand why. For example, the reason that the car jerks on gas, maybe a vacuum regulator of a corner of an advancing of ignition. This detail, usually located on the distributor. Characteristic twitching is more often than if the regulator is broken, and here replacement carburetor meaningless. How does the collector? The speed of combustion is always constant and the engine speed is increased, so we need to increase the speed of ignition of the fuel mixture while driving. If the rpm value from 1500 to 2000 centrifugal regulator in the car does not work, when driving at high speeds this task assumes that is a vacuum regulator of ignition angle. When you throttle on it is the vacuum in the diaphragm. It pulls the bearing and therefore increases the advance angle. Proper function of the hose check just enough. Close the tongue or finger at one of its ends -  the hose has a slightly “suck” this part of the body and remain hanging as inside a vacuum. But getting there air leads to the fact that when accelerating the car jerks.

As the originator of the occurrence of jerking when driving – spray accelerator pump (drivers often call it ‘maker”, “nose” or “push”). To see this detail and to assess the effectiveness of its work, you will have to remove the two removable diffuser and pressing the lever to see how it works “nose” in each chamber. Even if one of them fails, then it is cause for an unpleasant situation in which the car stalls and jerks. Repair is to: remove the atomizer, hold its lower part with pliers and pull out the bulb. Then clean the remaining part, blow through it and collect the item back. Avoid deformation, so the air must fall strictly within the diffuser and into the manifold, not on the wall. After install the atomizer at the same place, again make sure it is working – good detail gives a long straight stream. Removable diffuser should be installed correctly, i.e. close to the carb body. If the connection will remain in the space can lead to undesirable dilution.

Car jerks while driving: fault in the diaphragm

With the Failure of the diaphragm accelerator pump – the problem is very rarely diagnosed. It is reflected in the fact that the diaphragm remains only a spring and a closing button no. In this case it is possible to come up with its homemade equivalent, but often garages do not check the small details, and resort to a costly replacement of the carburetor.

Check the fuel filters

The Lack of fuel, which leads to shocks when moving the machine, may be due to a contamination of fuel filters. Their number varies depending on engine type. For example, in diesel engines there are two of them: for preliminary and fine cleaning of fuel. Most often, the latter is the reason why the car jerks when riding. To determine the condition of the first filter on the fuel consumer, you should disconnect the rubber hose from it and blow through the mesh. By performing this manipulation, do not forget about one the following condition: the fuel tank cap should be removed. Procedure a few days should be repeated, and not be limited to, cleaning fuel filters, and to add to that flushing the fuel tank. This will help prevent re-clogging of mesh and will extend the life of the filter. If when starting the car jerks still inspect the filter. Machines Japanese brands it is disposable, i.e. it does not need cleaning, but just need to put a new one. So after replacing the fuel flowed into the filter steadily, fill them in detail before start the engine. One hose running from the fuel tank with fuel, replace the clear tube and mouth pumped liquid into the filter. Then you can again put a regular hose and repeatedly click on the hand pump. Only then can you start the engine and assess its performance. This way you will be able to quickly fill the filter with the injection of fuel, only a hand pump will need much more time. To Restore the old fuel filter, clean off it from rust and dirt, too, but this is true for cars not made in Japan. To remove the filter, remove the mount of the transfer pump, Unscrew the bottom part from the plastic tube and the item itself. Don't be afraid of damaging its lower part, the clamping part of the vise: the filter component to be in it above, and the bottom third is a glass tank, it accumulates all the dirt. To clean the filter we will help with hot kerosene. To do this, pour clean kerosene into any metal container (bowl, pan, etc.), add a small amount of water (about a tablespoon) and put on fire. Naturally, the vaporization of kerosene aromas will not be called, so that data manipulation is recommended in well-ventilated area, in advance of bothering about the means of personal protection. Watching the water at the bottom of the pan, you can trace the heating of the kerosene. When the water boils, you can lower the capacitance of the filter after removing all plastic parts. Hold the filter with forceps, rinse it in a hot liquid. Optionally, after the water has evaporated to cool the kerosene, and then repeat the entire procedure again. As probably already became clear, the water here plays the role of temperature indicator. What does it do? In this way we evaporate from the filter the water and clean it from rust.

Boiling kerosene is able to clean the item from the paraffin precipitation, which are deposited on the grid if the car is using fuel with high content. Kerosene dissolves the paraffins and the filter after such a cleaning can extend their life by about ten thousand miles (of course, if you're not going to pour then in a tank of poor quality fuel). If you are afraid to break the filter element, it is not advised to blow compressed air. Some drivers deftly undone the system of fine filters, allowing them to use domestic filter model. The modernization is that the basic imported filter is complemented by the glass, which can be dismantled. Such processing is relevant if you are in places where it is impossible to repair vehicles or replace parts with new ones. But here you may encounter difficulties. Models Japanese replacement filters often have double walls with filling between them, so welding can be not only time consuming but also a fire hazard as a combustible filler. Also, speaking of filters, you need to keep in mind that if the pollution of this part, the engine may run rough, but not pulling the car. This is especially noticeable when riding the lift – the engine constantly stalls, sneezes. The fact that the engine lost power, you can determine by staying on the sidelines and began a hand pump to fill the fuel filter. In normal state the button should return to its original position, but when you press on the gas it will hold the pressure from the feed pump from the injection pump. If when braking the car jerks, this is the fault could be faulty clutch, or look for the reason in the automatic transmission.

Diesel engines are equipped with the same filtration systems, fine cleaning, so you can get to him easier – they do not depend on the engine type or brand of machine.

In some cases, the fuel system can be equipped with another mesh filter. It is located at the entrance of the fuel high-pressure pump, for example, it is on all cars, “Nissan”. To see and remove it, remove the bolts securing the tubing to the pump and see the plastic housing in which the part is installed. But in the car «Toyota» it will be placed differently: above it is the electromagnetic valve for fuel cutoff (in the stall). By the way, if you are the owner of a car with a diesel engine and noticed that at idle it revs “float” (that increase, then fall, then returned to normal), check the cleanliness of filters – often the presence of impurities leads to the appearance of this problem.

If we talk about gasoline engine...

What to do if you have a carbureted engine? In the beginning of the article we mentioned several situations in which the car twitches on the go at fault to improper operation of the carburetor. But the cause may be a thin fuel filters. The easiest way in this case, of course, to replace them, but not always on the road it can be done. If the problem was discovered in the trip and visit the shop is not possible, the first thing that can help – flushing of the filter is the reverse of the gasoline, since cars Japanese brands are most likely to be put on the straight rail to the fuel pump. This will help you to get at least to the nearest repair workshop or garage. Some drivers resort to puncture of the filter, however, this advice is not only wrong, but even harmful. Fibers, separated, undoubtedly fall into the carb very quickly displays this detail from the system, thus requiring replacement of expensive parts. If you do not have at hand the “native” filter, for example, «Toyota», you can use its counterpart from another car with a carburetor engine, in this case, these components are interchangeable and differ from each other only in diameter.

Some brands of cars (e.g., Honda) have a non-standard location of the fuel pump, therefore, the filter system will find the first time is difficult. But if your car jerks when driving and you want to fix it, here is some advice. Most often electric fuel pump will be located near the gas tank, and filters – in front of him. Don't forget that in engines of this type there is a third filter element. It is in the carburetor, at the place where the gasoline is received. To clean or at least inspect this item, it is often necessary to disassemble the carburetor, but in some vehicles (for example, “Nissan”) access to filter the grid much easier. The whole process of operation is as follows:

1. Unscrew the mounting bolt inlet.
2. Remove the nozzle.
3. To Get the filter mesh, which is directly under it and clean it.
4. To Put a filter into place and attach the nozzle.

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

1. Remove the top cover of the carb and turn her over.
2. Get the axis of the float.
3. Remove the float and shut-off the corner.
4. Next go to the needle valve and Unscrew his saddle (for this purpose, you need a small wrench or a flat screwdriver).
5. Remove the seat, turn it, clean the filter–the mesh on its reverse side.

Sometimes the complete lifting of the seat is not required, just after removing the shut-off needle to blow it with compressed air the hole. This simple manipulation will help to efficiently clean the filter. But the first filtration system, which passes the fuel in gasoline engines – this strainer is on the receiving tube in the tank. Cleaning like cleaning of the filters in diesel engines, about which we wrote above.

We now Turn to consideration of the problems of petrol engines, which can also cause you will feel the car twitch. As is clear, in detail we will disassemble the filtration system. It should be noted that the number of filters varies here depending on the location of the fuel pump. If it is inside the gas tank, the filtration system will consist of the receiving grid, fine filter and a mesh filter before the injectors. If the pump is mounted outside, besides already listed you can find the fourth – mesh cone filter located in the piping before the gas tank. If you want to pull it out and clean it, remove the first hose to the inlet of the fuel pump, then using tweezers you can gently have to remove the cone. But do not forget that if the above did not help, and the car jerks when driving, the injector in such cases must also be checked for correct operation.

Pulls the car? Check the spark!

The Defective work system sparking often pretends that the car begins to pull in Congress, with hills or on a flat stretch of road. For example, this problem was common in cars of the brand Nissan, soas their engine SA-18 was equipped with a contactless distributor. In case this part is a switch that malfunctions and lead to this specific vehicle. To fix the twitching can, only replacing the components.

The Culprit – control unit

Another possible reason why the car jerks during gear changes – the faulty operation of the control unit carb (in the English version, his name sounds like "emission control"). In this case, the nature of shocks would be random. To calculate the real cause of their appearance is quite difficult, as they are not permanent, but only appear occasionally while driving. If you suspect that the machine is something wrong, we recommend you contact the service center to do diagnostics of all systems on the bench. Also on the lift it is easy to see that the car twitch at idle. “Movement” of the vehicle when the wheels hang down usually helps not only to determine why the car pushes, but also to monitor “swimming” speed, which was already mentioned earlier. Often these two issues are connected, and only high-quality work of the mechanics helps determine the reason. And the culprit here is the control unit (EPI). Unfortunately, in this case, to discover the cause, you need to create certain conditions (feed speed of a specific size, a certain load), and to perform all of these conditions while riding impossible. Due to the traffic on the road, the engine is constantly changing, and there is an effect of jerking.

Conclusion

So, we have described almost all the variants of why the car jerks when riding. As you can see, the reasons for such movement are many, and not being an expert in car “toppings”, you will hardly be able to rectify the situation. But there are those moments when no professional equipment can not do, such as diagnostic at idle. In any case, if you notice tremors or jerking movements while driving, do not leave it unattended and be sure to visit the service center. Pay attention to the reputation of the Studio, read about it, visit the site in order not to fall into the trap of scammers. For many young drivers, cleaning the filters, for example, can be costly, so ask about the cost of services in advance. It is also useful to interview friends. But always remember: the operation of the vehicle, which twitches,  not only inconvenient, but dangerous, as it is fraught with accident. Be careful and good luck on the roads!