Sooner or later, every car enthusiast is faced with this phenomenon: the engine suddenly starts jerking, the car seems to twitch. It can happen at any time. During acceleration, sharp pressing of the gas pedal and even at idle speed. Why this is happening and how to deal with it, we will talk in this article.
The main reason for poor response to pressing the gas pedal
It is almost always the same: lean or vice versa - a rich fuel mixture. It is because of this that the engine crankshaft can continue to rotate even after the gas pedal is released, or vice versa, does not start to rotate immediately after the gas is pressed. The root cause is the wrong mixture. But there are many problems due to which the mixture becomes such. Let's list the most common causes of power failures and how to fix them.
Why does the car jerk when the accelerator is pressed smoothly
- In this situation, the engine responds with a delay to pressing the gas pedal. Jerks appear when the throttle valve remains open for a long time. At the moment of acceleration, the throttle position sensor (TPS) must send a signal to the electronic control unit (ECU) that the engine is switching from idle to load mode, therefore, more fuel must be supplied to the combustion chambers, and the total pressure in the fuel rail must be high. If the TPS is faulty, it does not send the above signal to the ECU (or it does, but with a delay). As a result, the pressure in the rail drops, the engine starts to twitch, and sometimes stalls. This malfunction occurs in injection engines, both on domestic cars (Lada Priora, Lada Granta) and on foreign cars (in particular, Ford Focus 2). The solution is obvious: the faulty sensor must be replaced.
- The same problem in injection vehicles can be created by the mass air flow sensor (MAF). He monitors the formation of the mixture and how much air enters it. If it is faulty, the car will start twitching, not having time to accelerate. This means that the mass air flow sensor should also be replaced.
- In carburetor cars (VAZ 2107, the first rare release of VAZ 2114), jerks during acceleration occur due to clogging of the outlet openings in the first carburetor chamber. Solution: The carburetor is removed and blown out with compressed air.
- In the classic VAZ models, the accelerator pumps of the carburetors often fail, and this also causes jerks when trying to get under way. It is impractical to repair this part, so it should be replaced.
Engine jerks while driving
Jerks, if you press the trigger sharply
The main reason for this is the "triplet" of the engine. That is, a situation when only three of the four cylinders of the car work. If the engine is troit, it simply does not have time to react in time, when you sharply press the gas pedal, and jerks occur. This problem applies to all types of engines. Here are the main reasons for its occurrence and ways to eliminate it:
- The oxygen sensor is not working properly. Solution: check with a multimeter, replace in case of malfunction.
- The engine has shifted valve timing. Solution: adjust according to the vehicle manual.
- Incorrect spark plug glow number. Solution: Check the manual for the glow number and install a new set of spark plugs with the correct number.
- The nozzles are clogged. Solution: remove them, install them on a stand simulating engine operation, and rinse with a special solvent.
- In addition, in carburetor cars, jerks when the gas is pressed sharply may appear due to the fact that the accelerator pump in the carburetor does not work correctly. Solution: the pump is removed, its atomizer is checked, then the diaphragm and valve channels. If they become clogged, they should be thoroughly blown out with compressed air.
You can read more about other possible reasons
Sometimes the owners of a car equipped with LPG begin to notice the unstable operation of their car at idle or under load. Incomprehensible jerks appear during movement, and the power leaves much to be desired. Why does it happen that the car jerks on gas, how to avoid such a state of an iron friend, and what could be the reason for jerks during movement, we will talk in today's article.
Idling
A common phenomenon is floating idle speed when operating on gas, quite often this occurs after a recent change of injectors in the LPG system. And the fact that after replacing the injectors with new ones, the car drove well for some time only confirms that this is precisely the problem. Or rather, the need for additional calibration of new injectors after the car has driven one to two thousand kilometers. If your problem is precisely the unstable operation of the car at idle, after the recent replacement of the injectors, be sure to contact a specialist who will calibrate and configure the system.
The problem is not HBO
Quite often it happens that the car jerks on gas while driving, not at all because of gas equipment, as the driver thinks, but because of a malfunction in the electrical part of the car.
Most often, drivers identify the following problems:
- The gap in the spark plugs and their serviceability in general. It is believed that the optimal gap should be in the range of 0.7-0.9 cm, although some motorists set the gap on the spark plugs up to 1.1. There are also special candles for running a car on gas, they differ from ordinary gaps and design. If the spark plug is faulty, it simply "breaks through", as a result of which the current follows the path of least resistance.
- High voltage wires. The second most common problem is the deterioration of high-voltage wires in a car. If your armored wires have covered more than 80,000 km. without replacement, it is best to replace them with new ones. An experienced electrician will help to identify a malfunction of one wire.
- The third most important is the problem with the auto ignition coil, if the problem is in it, the coil should be replaced with a new one.
- Gas mixture. The quality of the mixture can also have a serious impact on the behavior of the vehicle. Try changing the gas station to another.
The problem is in HBO
If all of the above options have been checked, and when the gas pedal is pressed sharply, the car still jerks on the move, then you should look for the problem in the incorrectly configured or failed LPG equipment. Basically, the problem with gas equipment lies in the unregulated air intake, as a result of which the car jerks. To identify such a malfunction, you should take a closer look at:
- Connections of all gas elements. As a result of long-term operation, depressurization of the connecting elements of the system is possible.
- Lines and rubber hoses that can dry out due to active use.
- "Anti-cotton". It is necessary to carefully check the cotton elastic and the installation location.
It is possible to identify the place of air leakage by “soaping” all of the above system elements. If a defect is detected, the hoses or connecting elements should be replaced, and then again check the tightness of the system.
It will not be superfluous to make an appointment with an experienced diagnostician, who, having connected the car to the computer, will identify problems with the ECU setting, calibrate and clean the nozzles, and also identify other possible problems.
One of the possible options for the car jerking when pressing the gas pedal while operating on gas may not be carried out in time
Suddenly it starts to work unstably under load: jerks while driving as if the fuel is at the bottom. At the same time, the gas is full. And it’s good if you didn’t have time to get far from the "gasman", but usually this happens at the most inopportune moment - when moving uphill, for example. By switching to petrol, the problem may disappear.
Practice shows that in 8 cases out of ten, the car jerks on the gas not at all because of gas, but because of problems in the electrical part. The reasons are as follows:
- Spark plug;
- High voltage wires;
- Ignition coils (ignition module).
Moreover, a defect in the electrical part may not appear when running on gasoline, or at idle speed on gas. The fact is that the gas ignites not as easily as gasoline, so the gas-air mixture requires more spark. Hence the increased requirements for the serviceability of electrical equipment and car equipment.
As for the armored wires, it is not always possible to detect their malfunction in the usual way - by observing the operation of the engine in the dark, with the hood open, therefore, if the wires are "stale", then they should be changed.
The remaining 2 cases out of 10, why does the car jerk on the move, accounted for, and for firmware errors. ECU settings and incorrect calibration of injectors manifest themselves immediately, and if there was no outside interference from outside, then they can be the last to sin on them. If necessary, the firmware can be "filled" with a new one, but it is better to entrust the calibration to specialists.
But defects usually appear over time, as a result of exploitation. They are mainly associated with air leakage, which occurs:
- At the connections of the entire gas distribution;
- On the body of the hoses themselves, as a result of drying out or chafing;
- At the installation site of the "cotton";
- On the gasket damaged as a result of regular frosting.
To, it is required to "wash" all connections and suspicious places. If necessary, replace hoses and renew connections.
By the way, if the coolant level is allowed to decrease, then the gearbox circuit “empties” first of all. As a result, the gas does not have time to evaporate, remaining in a liquefied state due to freezing.
Of the surprises, perhaps this is all, but to avoid them, it is necessary to be regularly serviced: most "suddenly" can be prevented.
The jerking of the car during acceleration can be caused by various reasons. In most cases, to detect this phenomenon, it is enough to simply check and listen to the operation of certain machine components. However, regardless of the reasons for this "behavior" of the car, it is necessary to eliminate the malfunction as quickly as possible, otherwise there is a possibility of getting more serious problems.
Dips and jerking on a carburetor engine
If the car jerks during acceleration and further acceleration, and there are also dips when pressing the gas pedal, first of all, it is recommended:
- Check or replace air and fuel filters. When they are heavily contaminated, the supply of air and fuel becomes difficult, which can lead to jerks.
- Unstable flow of fuel into the float chamber, which is usually associated with problems in the operation of the fuel pump. Replacing it allows you to solve the problem with jerks of the car.
- Insufficient fuel pressure. Checking the fuel pressure is carried out by connecting the pressure gauge to the fitting on the fuel line (for this, a piece of hose is used). With the engine running, the pressure in the fuel line should not exceed 3 kgf / cm2.
If the pressure does not correspond to this indicator, then the cause of the defect must be looked for in the following parts of the car: the fuel pressure regulator, the fuel filter or the fuel pump.
The reasons for "failures" (when you press the gas pedal, the car refuses to accelerate) and the accompanying jerks are often:
- The ignition coil together with high-voltage wires, which, due to long-term operation and wear, begin to "pierce", as a result of which the engine begins to triple. The solution to the problem is to replace the wires and coils.
- Spark plug. They cause jerks in the car as a result of heavy carbon deposits and poor contact with the wires.
Checking high voltage wires
To check the condition of the high-voltage wire, it is necessary to remove its tip suitable for the spark plug. Inside the winding there is a central core, which should fit as tightly as possible to the so-called. a metal penny placed in the tip of the wire.
This penny is designed to transmit current to the spark plug, and if there is no contact between the wire and the penny, then the current may not flow, as a result of which triplets occur. The main reason for the "failure" of the wire is its oxidation.
Checking for the fact of oxidation of the wire is carried out using the second probe of the multimeter, which must be touched to the central core of the high-voltage wire. If burnout is observed along the entire length, then the damaged area is determined by piercing the wire every 5-10 mm using a special multimeter tip. The damaged section, if the length of the wire allows it, is simply cut off; in other cases, the entire high-voltage wire changes.
Causes of jerking on injection engines
Injection engines, in comparison with carburetor versions, have better technical and operational characteristics. However, they also have a more complex design, so the reasons that cause the car to jerk during acceleration can be much more than for cars equipped with carburetors.
A feature of the injector is the presence of an electronic control unit for the fuel supply system, which is regulated using various sensors. The jerking of the car mainly causes problems with the following sensors:
- Mass air flow sensor.
- Throttle position sensor.
- Crankshaft position sensor (DPKV) - problems with this sensor are considered the most "unpleasant", since its failure leads to the termination of the injector operation, respectively, the possibility of starting the car is completely excluded.
The DPKV is checked by connecting a car oscilloscope to it. If the sensor is in good working order, clear pulses of the injector operation will be displayed on the device screen. In the absence of impulses or their blurring, it is necessary to promptly replace / repair the sensor. It is also advisable to carry out an additional check of the operation of other controllers, which can make it possible to identify malfunctions of the oxygen sensor or, for example, the electric valve of the injector, which can also lead to jerking of the car.
The reasons for jerking injection machines, as for carburetor vehicles, can be problems in the ignition system (plugs, ignition coil, high-voltage wires), as well as malfunctions of the fuel system (clogged fuel injectors and filter).
Another common cause of machine jerks is the use of low-quality fuel. Such fuel leads to the formation of a lean mixture, the characteristics of which are not enough for stable and high-quality engine operation.
In most cases, the problem of jerking the car during acceleration can be eliminated quickly enough, the main thing is to start repair work in a timely manner and prevent the appearance of more serious malfunctions.
To understand the possible cause of the breakdown, you should clearly identify the symptoms, and based on this, draw some conclusions.
When the car is warmed up to operating temperature, when you press the gas pedal, it starts to "dull" or twitch a little, and then, when accelerating, this problem disappears and the car works in normal mode.
If this problem occurs only during overclocking, and not, for example, when starting from a place, then the reasons will be the same. If the car jerks when starting from a standstill, then this may be a problem with the clutch or basket. If vibration is felt during driving and not only during acceleration, this may indicate a failure of the airbags that secure the engine.
Diagnostics can also be done at the service center. Especially if the car is injector, you need a special device. It is connected to the control unit and shows where and on which sensor the problem is possible. The same goes for diesel vehicles. A special stand is needed to test the injectors of a diesel engine. Without it, it is impossible to determine in what state they are.
Reasons for jerking during overclocking
There can be several reasons for the jerking of the car during acceleration.
Malfunctions in the engine ignition system
If the ignition is lost, then just during acceleration it will be strongly felt. This happens because when you press the gas pedal, fuel is injected into the cylinders, and detonation should occur there. If the ignition is set incorrectly or is out of order, then the fuel comes in, and the spark strikes at the wrong time. In other words, some part of the fuel is not ignited or ignites at the wrong time. Some cylinders may not detonate at all. This all leads to unbalanced work and, therefore, jerks. Defective candles or armored wires can also be the reason. It is advisable to change the candles sometimes. The spark plugs are checked on special equipment, where, at the same pressure as in the engine, it is checked whether the spark plug gives a spark.
Even when candles look good and free from defects, this does not mean that they are excellent at work. It is recommended to buy candles from not the cheapest manufacturer, since even new ones may not pass the test stand.
The armored wires are checked with an ohmmeter for the presence of the required resistance. You can also check the quality of the wire connections with candles. The procedure should be carried out with a warm engine. It is necessary to collect water in a bottle and, using a sprayer, distribute it with the engine running to the armored wires and the connection with the candles. If the engine speed starts to decrease and the car starts to run, then the wires should be replaced.
If there is no understanding of how the ignition is exposed, then it is better to contact a specialist. This process is quite accurate, you should not make mistakes there.
The most common reason for jerking a car during acceleration is a malfunction in the power supply and fuel supply system. When you press the gas pedal due to contaminated elements of the fuel system, there is not enough fuel to accelerate. That is why jerks occur during acceleration.
The problem might be:
- Filters. The air filter and fuel filter must be changed regularly. This is a consumable that quickly breaks down.
- Dirty fuel supply systems. In carburetor cars, these are jets, in which the slightest dust or bits of dirt strongly affect the fuel supply. Injector nozzles can get clogged.
- Fuel pump. If it fails or partially begins to show lower performance, namely, it does not have time to pump the required fuel pressure into the system, then during acceleration this deficit will be visible.
There are various aerosols and additives for cleaning fuel systems. If you choose a product from a trusted manufacturer, they work very well. But this may not be enough in all cases. There are cases that require mechanical cleaning or repair of individual parts. The valve or some other part of the mechanism may fail.
Other defects
Poor-quality fuel can be attributed to other reasons. When filling with low-quality fuel, which is very different from the previous one, you may feel a drop in power or "stupidity" when you press the gas pedal. If everything was fine, and then you went to a gas station, where you have not yet been, and it was after this that the problems began, then the conclusion is obvious. This problem is very common in gas vehicles.
Elimination of identified problems
After the cause has been identified, you can begin to eliminate it. In most cases, this work should be entrusted to specialists. After all, not always the reasons that at first glance were key are just such. Correct ignition setting, carburetor, injector adjustment is what is better to entrust to a knowledgeable person. If it was found that the jerking was caused by dirty filters, you can use an aerosol cleaner. It is sprayed into the opening of the air filter. Also, additives in the fuel tank show themselves quite well. These additives clean the fuel lines and all other elements. XADO additives have proven themselves well.
