Why does the car twitch while driving? Reasons why the car twitches at idle, when shifting gears, when braking and at low speeds

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

Drivers sometimes notice that when switching automatic transmission, the car twitches unexpectedly, the same thing happens on descents, when climbing, and so on. What is the reason for this behavior of the vehicle? There are a lot of reasons, but under any conditions, a twitching car can become an involuntary 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 is twitching on the gas?" It seemed like a strange question. But if you already clearly feel shaking in the car, then the problem has reached its climax and has become too obvious. And, as you know, any problem is easier to prevent than to fix. 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.

I must say right away that checking the carfor the presence / absence of jerking movements at idle is incorrect (except in rare cases), this can only be done while driving. Having chosen a flat safe section of the road, alternately change gears. On each of them, sharply press the gas pedal. The machine should respond only to your pressing, even the lightest. If the car jerks without your desire or jolts are felt when lifting, then you need to look for the causes of this problem.

Car jerks while accelerating…

You are gaining momentum, and the car starts to jerk, its movement ceases to be smooth? The reason lies in the intermittent flow of fuel into the float chamber: it disappears from there faster than it enters. The fuel pump supplies fuel there, so it could be a malfunction. How to "cure" it? To do this, remove the fuel pump cover and carefully inspect the hole where the valve should be. Often the o-ring lies nearby, and not in place, or is completely absent. Due to depressurization, there are interruptions in fuel injection, and, consequently, the car twitches on the go. Repair in this case consists in replacing the valve and restoring the tightness of the system. You can also do it yourself if you have a new O-ring of a suitable diameter and a tool. This work will take half an hour at most, and a professional can do it in 5 minutes.

Jerks when driving at low speed

If the machine twitches at low speeds, then you should check the operation of the nozzles. Carefully inspect the harness too - if it lies directly on the fuel pipe, it mayfray. This will lead to the fact that when the wires touch the tube, the wiring will close and the injection nozzles will turn off. Replacing the wiring should fix the problem.

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

If the car twitches when you press the gas, then in order to eliminate this defect, you should figure out what is the reason. For example, the cause of the car twitching on the gas may be a vacuum ignition regulator. This part is usually located on the distributor. A characteristic twitch occurs most often if the regulator is broken, and here replacing the carburetor is pointless. How does a vacuum cleaner work? The rate of fuel combustion is always constant, and the engine speed increases, which means that we need to increase the rate of ignition of the fuel mixture while driving. At speeds ranging from 1500 to 2000, the centrifugal regulator in the car does not work; when driving at high speeds, it is the vacuum ignition angle regulator that takes over this task. When the throttle is open, a vacuum occurs through it into the diaphragm. This pulls the bearing along, and therefore increases the lead angle. It is quite easy to check the correct operation of the hose. Close one of its ends with your tongue or finger - the hose should “suck” this part of the body slightly and remain hanging, since there is a vacuum inside it. And getting air in there just leads to the fact that during acceleration the car twitches.

Next culpritthe occurrence of twitching while driving - the accelerator pump sprayer (drivers often call it a "kettle", "spout" or "samovar"). To see this detail and evaluate the effectiveness of its work, you will have to remove two removable diffusers and, by pressing the lever, see how the “nose” works in each of the chambers. If even one of them fails, then this is an occasion for an unpleasant situation in which the car stalls and twitches. The repair is as follows: remove the atomizer, clamp its lower part with pliers and pull out the ball. Then clean the rest, blow it out and put the part back together. Avoid deformation, so the air must enter strictly into the diffuser and into the collector, and not onto the wall. After installing the sprayer in its original place, check its operation again - a serviceable part gives a long, straight stream. The removable diffuser must be installed correctly, that is, close to the carburetor body. If space is left at the junction, unwanted vacuum may occur.

Car jerks while driving: Diaphragm failure

Breakage of the accelerator pump diaphragm is a very rarely diagnosed problem. It is expressed in the fact that only a spring remains on the diaphragm, and there is no button to close it. In this case, you can come up with its home-made counterpart, but often in auto repair shops they do not check for the presence of this small part, but resort to an expensive replacement of the carburetor.

Checking fuel filters

Lack of fuel, which causes jolts when driving, may be due toand dirty fuel filters. Their number varies depending on the type of engine. For example, in diesel engines there are two of them: for preliminary and fine fuel cleaning. Most often, it is the latter that is the reason that the car twitches while driving. To determine the condition of the first filter on the fuel receiver, you need to disconnect the rubber hose from it and blow through the mesh. When performing this manipulation, do not forget about one obligatory condition: the fuel tank cap must be removed. The procedure after a few days should be repeated, and not limited to cleaning the fuel filters, but add to this the flushing of the fuel tank. This will help to avoid re-clogging of the mesh and extend the life of the filter. If the car still twitches when starting, inspect the fine filter. For Japanese brand cars, it is disposable, that is, it does not need to be cleaned, but you just need to put in a new one. To ensure that fuel enters the filter confidently after replacement, fill the part with it before starting the engine. To do this, we replace one hose coming from the fuel tank with a transparent tube and inject liquid into the filter with our mouth. After that, you can put the standard hose back on and press the hand pump several times. Only after that you can start the engine and evaluate its work. This way you can quickly fill the filter, when pumping fuel only with a hand pump, it will take much more time.

Restore the old fuel filter, cleaning it of rust and dirt, tooYou can, but this is true for non-Japanese cars. To remove the filter, remove the booster pump mount, unscrew the lower plastic plug and the part itself from the part. Do not be afraid to damage its lower part by clamping the part with a vise: the filter component is higher in it, and the lower third is a settling glass, all impurities accumulate in it. Hot kerosene will help us clean the filter. To do this, pour pure kerosene into any metal container (bowl, pan, etc.), add a small amount of water to it (approximately a tablespoon) and put on fire. Naturally, the fumes of kerosene cannot be called aromas, so these manipulations are recommended to be carried out in a well-ventilated area, taking care of personal protective equipment in advance. Following the water at the bottom of the pan, you can trace the heating of kerosene. When the water boils, you can lower the filter into the container, after removing all the plastic parts from it. Hold the filter with tweezers and rinse it in the heated liquid. If necessary, after boiling the water, cool the kerosene, and then repeat the whole procedure again. As it has probably already become clear, water here plays only the role of an indicator of temperature. What is it for? In this way, we evaporate water from the filter and clean it of rust.

Boiling kerosene can also clean the part from paraffin deposits that settle on the grid if the car uses fuel with a high content of paraffin. Kerosene dissolves paraffins, and the filter after such cleaning can serve you for about ten morethousand kilometers (of course, if you don’t fill the tank with low-quality fuel after that). If you are afraid of tearing the filter element, we do not recommend blowing it with compressed air. Some drivers cleverly redesign the fine filter system, which allows them to use domestic filtration models. Modernization consists in the fact that the basic imported filter is supplemented with a glass that can be disassembled. Such processing is relevant if you are in places where it is impossible to repair a vehicle or replace a part with a new one. But even here you can run into difficulties. Models of Japanese replaceable filters often have double walls with a filler between them, so welding can become not only laborious, but also fire hazardous, since the filler is flammable. Also, speaking of fine filters, it must be borne in mind that if this part is contaminated, the engine may work intermittently, but at the same time it does not jerk the car. This becomes especially noticeable when driving uphill - the engine constantly stalls, sneezes. The fact that the engine has lost power can be determined by stopping on the side of the road and starting to fill the fuel filter with a hand pump. Normally, the button should return to its original position, but when you press the gas, it will be kept pressed by the pressure from the feed pump from the injection pump. If the car twitches during braking, then the clutch discs may be to blame, 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 match parts to them -they do not depend on the type of engine or brand of machine.

In some cases, the fuel system may be equipped with another strainer. It is located at the inlet of the high pressure fuel pump, for example, it is on all Nissan cars. To see and remove it, remove the bolt that attaches the piping to the pump and you will see the plastic housing in which this part is installed. But in Toyota cars, it will be installed a little differently: above it there will be an electromagnetic valve for cutting off the fuel (participates in engine shutdown). By the way, if you own a car with a diesel engine and notice that when idling, its speed “floats” (they increase, then fall, then return to normal), check the cleanliness of the filters - often the presence of dirt in them leads to this problem.

Speaking of a carbureted engine…

What if you have a carbureted engine? At the beginning of the article, we already mentioned several situations in which the car twitches on the go due to the fault of the carburetor. But fuel fine filters can also be the cause. The easiest way in this case, of course, is to replace them, but this can not always be done on the road. If the problem was discovered on a trip and it is not possible to visit a car repair shop, the first thing that can help is flushing the filter with gasoline in reverse, since on Japanese cars it is most often placed on a direct guide to the fuel pump. This will help you get to at leastnearest car service or garage. Some drivers resort to piercing this filter, but such advice is not only wrong, but even harmful. The lint that comes off will undoubtedly get into the carburetor, which will very quickly disable this part, so this expensive part will need to be replaced. If you don’t have a “native” filter at hand, for example, from Toyota, you can use its counterpart from another car with a carburetor engine, in which case such components are interchangeable and sometimes differ from each other only in diameter.

Some brands of cars (for example, Honda) have a non-standard location of the fuel pump, therefore, it will be difficult to find a filter system the first time. But if your car is jerking while driving and you want to fix it, here are some tips. Most often, the electric fuel pump will be located next to the gas tank, and the filters in front of it. Do not forget that in engines of this type there is also a third filter element. It is located in the carburetor itself, in the place where gasoline enters. 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 mesh is much easier. The whole process of work is as follows:

1. Unscrew the fixing bolt of the inlet pipe.
2. Remove the tube.
3. Retrieve the filter mesh directly below it and clean it.
4. Replace the filter in its original place andattach the nozzle.

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 out the float axle.
3. Remove the float and locking corner.
4. Next, go to the needle valve and unscrew its seat (for this purpose you will need a small wrench or a regular flat screwdriver).
5. Remove the saddle, turn it over, clean the mesh filter on its back side.

Sometimes it is not necessary to completely remove the seat, it is enough just to blow out the resulting hole with a jet of compressed air after removing the locking needle. This simple manipulation will help to clean the filter efficiently. But the first filtration system that fuel passes through in carbureted engines is a strainer on the intake pipe in the gas tank. Its cleaning is similar to cleaning the filters in diesel engines, which we have already written about above.

Let's move on to the problems of gasoline engines, which can also cause you to feel like the car twitches. As it is already clear, we will analyze in detail its filtering systems. It must be said right away that the number of filters here varies depending on the location of the fuel pump. If it is inside the gas tank, then the filtration system will consist of a receiving mesh, a fine filter and mesh filters in front of the injectors. If the pump is brought out, then in addition to those already listed, it will be possible to find the fourth - a mesh cone-shaped filter,located in the pipeline in front of the gas tank. If you want to pull it out and clean it, first remove the hose for the fuel pump inlet, after which you can carefully remove the cone with tweezers. But do not forget that if the above did not help, and the car twitches while driving, the injector in such cases must also be checked for serviceability.

Jerking the car? Check the spark

Defective operation of the sparking system most often reveals itself by the fact that the car starts to jerk when driving off a hill or on a flat stretch of road. For example, such a problem was often encountered in Nissan cars, since their CA-18 engine was equipped with a contactless distributor. There is a switch in the body of this part, failures in its operation lead to such a specific movement of the car. The only way to fix the twitching is to replace the components.

The culprit is the control unit

Another possible reason why the car twitches when shifting gears is a malfunction of the carburetor control unit (in the English version, its name sounds like “emission control”). In this case, the nature of the shocks will be random. Calculating the real reason for their appearance can be quite difficult, since they are not constant, but only occasionally appear when driving. If you suspect that something is wrong with the car, we recommend that you contact a car service, make a diagnosis of all systems at the stand. Also on the lift it is easy to see that the car twitches at idle. "Movement" of the carhanging wheels usually helps not only to determine why the car is pushing, but also to track the “swimming” of revolutions, which we already mentioned earlier. Often these two problems are connected, and only the quality work of auto mechanics helps to determine what is the cause. And the culprit here is the control unit (EPI). Unfortunately, in this case, in order to find the cause, it is necessary to create certain conditions for the operation of the car (delivery of revolutions of a specific value, a certain load), and it is unrealistic to fulfill all these conditions while driving. Due to driving on the road, the operation of the engine is constantly changing, and a twitching effect occurs.

Conclusion

So, we have described almost all the options for why the car twitches while driving. As you can see, there are a lot of reasons for such a movement, and without being an expert in automotive "stuffing", you are unlikely to be able to correct the situation. But there are also such moments when you cannot do without professional equipment, for example, this concerns diagnostics at idle. In any case, if you notice jolts or twitches while driving, do not leave it unattended and be sure to visit a car service. At the same time, pay attention to the reputation of the workshop, read reviews about it, visit the site so as not to fall for the bait of scammers. For many novice drivers, cleaning filters, for example, can cost a pretty penny, so ask about the cost of services in advance. It is also useful to ask friends. But be sure to remember: the operation of a car that twitches is not only inconvenient, but also dangerous, as it is fraught with an accident. Be careful and good luck on the roads!