There can be many reasons for failures during acceleration, but in any case they can be roughly divided into two main groups: problems with ignition (in the case of gasoline engines) and problems with the power supply system.
Bad fuel
Unfortunately, poor-quality fuel can often cause failures during acceleration. For example, if water is caught in it. Of course, the engine on this will work intermittently. There are two ways out. If you are "lucky" to fill a full tank with such "fuel", then it is better not to be lazy and drain it so as not to ruin the injectors and the fuel pump. Or be patient and just work out low-quality gasoline or diesel.
Clogged air and fuel filters
A clogged air or fuel filter often causes poor engine performance and dips during acceleration. The only solution is to replace the filter.
Spark plug
The first step is to check the spark plugs. Large carbon deposits on the electrodes lead to misfiring and, as a result, engine failure. Hence the nervous acceleration. Of course, if you have financial difficulties, you can try cleaning the candles. But it's much easier to simply replace them.
High voltage wires and ignition coils
If it's not about candles, the cause may be faulty coils or breakdowns in high-voltage wires. Of course, no repairs will help here, only a replacement. The modular unit responsible for the ignition may also be faulty. Only diagnostics will help to find out the cause of its malfunction, and even then not in all cases.
Clogged or defective injectors
It doesn't matter if you have a diesel engine or a gasoline engine. Clogged or defective injectors can cause jittery motor operation. In the first case, it will most likely help. By the way, in the presence of a throttle valve, dips in the operation of the motor can also be caused by its contamination. Worse if the nozzles are already worn out. For some models, a repair kit is provided. But in most cases you will have to change them.
Mass air flow sensor or crankshaft position sensor
Failure of these sensors can also cause the engine to run roughly. Incorrect data on the amount of air entering the engine leads to incorrect opening times of the injectors and, as a result, incorrect preparation of the fuel mixture. The crankshaft position sensor can also cause confusion, due to which the moment of opening the injectors and the formation of a spark in the spark plugs will be selected incorrectly. Hence, the uneven operation of the engine with dips during a set of revolutions. Diagnostics will help determine the faulty sensor. Such a sensor will have to be replaced.
Incorrect calibration of the engine control unit
In many cases, a malfunction of any sensor or the same ignition module will be reported by the "Check Engine" icon on the instrument panel. But there are times when everything works normally and there are no malfunctions, but the engine still suffers from failures when gaining speed. This is due to the incorrect calibration of the control unit. Moreover, such symptoms may not appear in all cases. And, for example, only in an unheated state. A striking example is. In a cold state, her engine suffered from slight dips during a set of revolutions due to the fact that an insufficient amount of fuel was clearly entering the cylinders.
In this case, all that remains is to wait for the updated software of the control program, in which all errors will be corrected. As for the other culprits for overclocking failures - apart from worn out injectors and problems with the ignition module - as a rule, the reasons are not fatal. The main thing is not to delay their elimination.
Sooner or later, every car enthusiast is faced with this phenomenon: the engine suddenly starts to work in jerks, 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 classic VAZ models, accelerator pumps of 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 if faulty.
- 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.
- Nozzles 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
Many car owners, both domestic and foreign, often face the problem of jerking the car when the gas pedal is pressed. There are many reasons for this behavior of the car. Therefore, we suggest further familiarizing yourself with the most common malfunctions that cause such jerks, as well as their symptoms and remedies.
1 Malfunction of fuel system sensors
A frequent cause of jerks when pressing the gas pedal is a malfunction of the TPS, especially this often happens in "VAZ" models. This sensor detects the position of the throttle valve. It is quite simple to identify its malfunction, thanks to a characteristic symptom - the car starts to "jump" during acceleration, even if the accelerator pedal is pressed very smoothly.
Most often, as a result of a TPS malfunction, the throttle valve remains in a slightly open position for a long time. When you press the gas pedal, the sensor does not immediately transmit a signal to the computer. As a result, the engine at first cannot change the operating mode, and then the fuel is supplied abruptly and in a large volume. As a result, the engine starts to "choke" and work in jerks, and sometimes even stalls.
There is only one way to solve the problem - to change the sensor. True, some car services offer controller repair. But, as practice shows, the repaired TPS serves no more than one or two months. Therefore, it is better to buy a new part right away. In the photo above, you can see the location of the TPS in a VAZ 2114 car.
Another sensor that causes the car to jerk when it fails is the air flow sensor (DFID). In the event of a breakdown, the engine starts to work unstably with any press on the gas. As in the previous case, the problem is solved by replacing the sensor. Sometimes the problem is not the sensor itself, but the air duct (corrugation) that goes from the air filter to the engine. As a result of its depressurization, air can be leaked bypassing the sensor, which causes malfunctions in its operation.
In some cars, jerking when accelerating at idle can occur as a result of a failure of the crankshaft position sensor (DPKV), which is located near the oil pump. The photo below shows the location of the DPKV of the Priora car with the 21126 engine, i.e. having 16 valves.
To test the operation of this controller, you need to connect an oscilloscope to it. Smudged or barely noticeable pulses indicate that the sensor is really not working correctly. Please note that if it is completely out of order, the car stops starting altogether.
2 Problems in the fuel supply system
Often the car starts to jerk when starting off and picking up speed as a result of a lack of fuel in the float chamber. Most often, the malfunction manifests itself when the gas is pressed sharply. This is due to the fact that fuel is burned in the engine much faster than it enters the float chamber.
There are several reasons why such a situation may arise. Typically, fuel interruptions occur as a result of a malfunctioning fuel pump. To resolve this issue, you can follow these steps:
- Remove the pump cover.
- Examine the surface of the lid. Replace the O-ring if necessary.
- If chamber depressurization or other fuel injection problems are found, the worn parts must be replaced.
Most often, the fuel pump is located under the hood. However, on some vehicles, it may be located at the back. For example, in the VAZ 2110 and VAZ 2112 models, to access the gas pump, you need to dismantle the back seat and unscrew the cover, as shown in the photo below.
Sometimes the cause of all problems in the fuel supply system is trivial - the fuel filter is clogged. If it is not replaced in time, it can become clogged to such an extent that the fuel supply will stop altogether and it will be impossible to start the car.
3 Malfunction in the mixture preparation unit
If the car dulls when picking up speed and starts twitching when the gas pedal is pressed sharply, it is quite possible that the malfunction lies in the mixture preparation unit, i.e. carburetor or injector. Most often this occurs as a result of clogged nozzles, air passages or nozzles. Car owners usually encounter a similar situation in the spring, after a long idle time or after filling with low-quality fuel.
In some carburetor cars, for example, the VAZ 2109, you can correct the situation without even removing the carburetor. To do this, you just need to dismantle the air filter located above the carburetor, and then blow out all the channels with a hand pump with a tapered tip. It is advisable to carry out the work together, so that one person substitutes the tip to the canals and holds it, and the second, with sharp and powerful movements, works with the pump.
Of course, such manipulations will not give a 100% result, moreover, the situation will not improve for a long time. But if the problem happened on the road, blowing with a pump can really help out. For normal cleaning, you need to contact the service center, where specialists will rinse the carburetor with a special agent. The situation is exactly the same with the injector: the only way to remove blockages is by flushing. Moreover, for this it is necessary to use a special tool for injectors.
It should be carried out on a special stand that simulates the operation of the engine, therefore it is impossible to perform it independently.
4 We are looking for the reason in the electrician
Very often, the cause of the car jerking and slow speed up is the engine "undermining" due to faults in the ignition system. In this case, when the gas pedal is pressed smoothly, the problem is often not noticeable at all, but when pressed sharply, the engine seems to "choke". At high revs, "podtraing" also may not be felt. In motion, jerks can occur only at certain speeds or when the car is moving uphill.
Most often, replacement of candles helps in such a situation. However, candles are not always the problem. Often, "podtraing" occurs due to problems with high-voltage wires that go from the distributor to the candles. You can identify a faulty wire by simply listening to the wiring while the engine is running. A wire that has a "breakdown" emits a characteristic clicking sound. In the dark, you can even see a spark. True, in some cases, the wires fail asymptomatically, therefore, the faulty element can only be identified by alternately replacing the wires.
Sometimes the problem is not even caused by the wires themselves, but by the tips on the coils and candles. Accordingly, it is easily solved by replacing the tips.
These are all the common reasons why the car begins to twitch when you press the gas pedal suddenly or even smoothly with your foot. If, after completing all the above steps, you did not succeed in resolving the problem, contact the service center, where specialists will perform computer diagnostics and determine the exact cause of the malfunction. Often, you get rid of jerks only after flashing the on-board computer.
Sooner or later, every car enthusiast has to face the following problems:
- The appearance of malfunctions in the valves;
- Sharp jerks of the car (there is a feeling that it twitches by itself);
- Lack of instant response of the engine to pressing the gas pedal.
Moreover, when you press the gas pedal, the car begins to twitch not only when idling, but also during acceleration and at full speed of the vehicle. To understand how this happens, what is the reason and what needs to be done to correct the situation, it is necessary to move from the symptoms to the causes of the breakdown.
The main reason for the "jerking" of the car when you press the gas pedal
The main cause is most often associated with an oxygen rich / depleted fuel mixture. It is because of the lack of air that the crankshaft continues to rotate despite the fact that the gas pedal has long been released. In addition, when the pedal is pressed sharply, the motor jerks and rotates in place.
The root cause of the problem is the preparation of the wrong mixture. In turn, the mixture can be supplied to the engine in different ratios due to malfunction of other devices and components of both the engine and the fuel system.
Twitching of the car due to a malfunction of the TPS
The second sensor that affects the supply of air to the system is the device for adjusting the mass flow of oxygen in the system. It works in the injection type of engines and is responsible for supplying air when the fuel mixture is formed. If this component is defective, then your car will also twitch, not even having time to accelerate. The solution is similar with the first sensor - dismantling and complete replacement of the mass air flow sensor.
Jerking the car - a malfunction in the carburetor chamber and pump
In the event that the engine starts to work with jerks in carburetor machines even with a weak pressure on the gas pedal, the main attention should be focused on the carburetor chamber. The problem is often associated with clogged outlets that are located in the first of the carburetor chambers.
When the fuel enters the engine, it takes with it part of the burning and metal shavings, as a result of which the mixture undergoes changes and the engine runs unstable. You can solve this problem yourself - just remove the carburetor and blow out all its pipes and openings with compressed air.
A classic example is the following situation: when the pump is damaged. As a result of the failure of the accelerator pump of the carburetor, the mixture is supplied to the engine in an incomplete volume. The result is the appearance of jerks during even a smooth pulling off attempt. In most cases, it is impractical to repair pumps, which is why they are simply changed in a car service.
carburetor chamber
Twitching the car during acceleration
Such a problem can manifest itself with a smooth set of revolutions, which is accompanied by a sharp short jerking of the vehicle. In this case, the reason is associated with the lack of a constant flow of the fuel mixture into the float chamber of the motor. That is, the fuel is burned in the chamber much faster than the fuel pump distills the new flow. As a rule, it is possible to find a breakdown in the design of the gas pump.
The solution to the malfunction of the fuel pump takes place in 3 stages:
- Remove the top cover of the pump and carefully examine the surface of the hole where the valve structure should be located;
- If the O-ring is abraded or missing, fix a new one;
- If, during the diagnosis, a chamber depressurization is detected or the problem is related to interruptions in fuel injection, then the final stage will be associated with a complete replacement of the inoperative valve and further restoration of the sealed state in the system.
Advice: when repairing, do not try to patch up holes in the old cylinder and reinstall it. This can further lead to overhaul of the entire engine structure.
fuel mixture
The appearance of jerks in the car with a sharp press on the gas
If the reason is not related to the gasoline pump, then these symptoms may indicate the so-called "triplet" of the engine. A situation arises in the machine in which only one of the 4 cylinders can work correctly. As a result of "triplet", the motor simply cannot respond in time to pressing the gas pedal, after which such problems arise. You can deal with the breakdown in the following ways:
- If the oxygen supply sensor is not working correctly, the system is diagnosed using a multimeter. In the event of a malfunction, it is simply replaced.
- If the valve timing in the motor is shifted, it is necessary, with the help of car service specialists, to adjust them according to the appropriate instructions.
- The detection of an incorrect glow plug number is solved by installing a new set with the correct number.
- The problem of clogged nozzles can only be solved in a car service. To do this, they are installed on a special stand that simulates the operation of a motor, and washed with a special solvent.
- Also, a problem can arise when the emulsion tube and well located in the structure of the second chamber of the carburetor motor are clogged. The only solution here is to flush the carburetor and tube with kerosene.
Engine jerking due to problems with the ignition system
If, when the car picks up speed, you observe sharp drops in power, then the reason lies in the malfunction of the elements of the ignition system. This problem applies to any of the engine types. The only correct solution is to check the ignition with the engine off. It is carried out by the following features:
- The tightness of fixing the blocks with wires is checked;
- The absence of chips and the good condition of the coil;
- Serviceability of the wiring connecting the ignition system to the engine.
After checking all the elements, you need to start the car and just listen to how the engine began to work. If you find the appearance of characteristic clicks, then there are small high-voltage breakdowns in the system. In this case, you will have to buy all the elements of the ignition system - a coil, a block and a set of high-voltage wires.
Advice: do not try to replace the wiring on the machine yourself. Only highly qualified specialists can use the instructions and the diagram to correctly connect the relays and fuses, after which the ignition system will not burn out. You can also check the wheels at the same time by comparing the indicators in.
If the engine runs smoothly, the problem may lie in the spark plugs. And they ate to be more precise - in the absence or rare appearance of a spark. The presence of defects in the sparking system can be easily detected if the car engine starts to jerkily when descending hills and even on flat sections of the road.
For example, the problem with a set of candles is typical for vehicles under the Nissan brand. This is due to the equipment of their engine model CA-18 with a special design of a contactless distributor. The distributor housing contains a switch, in the event of a malfunction of which the signal about the spark does not go to the on-board computer, and such a specific movement of the machine occurs. It is possible to correct the jerks of the motor only with a complete replacement of the distributor components.
If the set of candles is also in excellent condition, the only remaining reason can only be malfunctions in the operation of the control unit of the carburetor type of the motor. At the same time, jerks do not occur constantly, but accidentally and only during a long car ride.
It is possible to detect faults in the control unit only after diagnostics in a car service at a special stand. Also, with the help of the lift, it will be possible to see that the car at idle speed occasionally twitches. As a result, the control unit (EFI) should be replaced along with the breakdowns found in other parts of the vehicle.
car pads
Video: the car jerks when driving - several reasons
Most car enthusiasts are faced with the problem of motor jolts during smooth or sharp acceleration. This problem is not critical and can be easily repaired. Moreover, users of both domestic VAZ 2112 on block 16, and owners of foreign cars like Hyundai Solaris are not insured against this. If the car jerks when you press the gas pedal, you need to investigate such units.
- Fuel supply. As a rule, problems with acceleration begin after refueling at a questionable gas station.
- Air in the system. Suction of excess oxygen through cracks or leaky clamps may also occur.
- Ignition. This topic is worthy of a separate issue.
- Pressure lines. Fuel pumps, ramps, injectors, filter inserts are blocks that require special attention.
So, you should figure out what to do when the car starts to twitch during acceleration.
Diagnostics
The diagnostic procedure for different engine designs is performed according to a different algorithm. However, there are general faults.In the process, it is necessary to check the fuel system, air supply lines, and the ignition device. In this case, the troubleshooting is carried out alternately for all units. If the sequence is successful, the damaged node is changed to a known good (new) one.
What to do
In the absence of knowledge or lack of confidence in your own abilities, you can ask for help at the service station, where the masters will conduct a diagnostic examination and repair the car.
If the user decided to figure it out on his own, do the following.
When piling on the gas, the car jerks and does not go
In the case when the car behaves predictably at idle, and when the trigger is pressed, jerks are felt, and the car slowly picks up speed. The matter lies in the lean or re-enriched mixture entering the cylinders. It does not matter whether it is an old VAZ or a new modification of the Hyundai Accent type. The original source is located here.
The secondary question is how this happens, because in 50% of cases the carburetor or injector is set up correctly.
The car jerks during acceleration and a sharp press on the gas
A similar symptomatology occurs on injection foreign cars - when the trigger is pressed firmly, the car pulls. In this case, acceleration occurs in normal mode. For cars such as "Ford Focus", "Opel-Astra J", "Chevrolet Cruz", the case may be in the breakdown of the ECU, DMRV, DPDZ. Also, the problem is not bypassed and modifications of the VAZ 2114, Audi A6 C5.
The easiest diagnostic method is to replace parts with known new ones. Thus, the throttle position sensor can "blunt" by incorrectly indicating to the ECU the location of this unit, which causes a variable opening of the throttle with all the ensuing consequences. Also, the DMRV may misinterpret the indicators, which will cause the mixture to deplete.
When you press the gas pedal, the car dulls, then jerks sharply
When the vehicle dulls during acceleration, followed by a sharp jerk, and then the dynamics stabilize. You need to check the following items:
- air line;
- accelerator pump;
- fuel quality;
- main fuel pump;
- ignition settings;
- MRV sensor.
The owners of the Lada Priora car periodically face the problem of fuel pump failure. Here it will be enough to replace the element with a new one, to insure it, to clear the highways (low-quality fuel could get in).
Also, in some cases, the engine begins to triple and then accelerate. Here, the mass air flow sensor is ringing, spark plug diagnostics, ignition angle check, nozzle blockages.
Additionally, if there is an automatic transmission, it is necessary to check this mechanism. About 20% of visits to a car service with similar malfunctions end with a "surprise cure" inside the torque converter.
The car jerks on the move when you press the gas pedal slightly
A more exotic malfunction, when, when the trigger is smoothly pressed, the car begins to twitch before reaching a certain speed of the power plant. Here, there is a shortage of combustible mixture in the float chamber of the internal combustion engine - gasoline burns out faster than it has time to enter. This is a side effect of a faulty fuel pump, the unit does not have time to pump a new portion of the mixture, which provokes the motor jolts.
Note! On independent structures like the carburetor Oka or the injection "Lanos", the breakdown in 90% of cases manifests itself in the same way, which narrows the search area.
Auto twitches when you press and release gas
If, when the speed is reduced, the car starts to nod off, and during acceleration it twitches again, there can be two sources of the problem.
- Failure of sensors. Defective sensors send incorrect data to the ECU, causing a failure in the uninterrupted fuel supply.
- Clogged metering elements (nozzles, jets). Owners of classic models of the VAZ 2107 type often face a similar problem. A clogged nozzle, after the gas is released, "spits out" part of the fuel, which causes an increase in speed. With a sharp acceleration, the element does not have time to supply the required amount of the mixture into the cylinder.
Carburetor car jerks when you press the gas
If a problem is detected on carburetor cars such as VAZ 2109/2106. First of all, you need to pay attention to the fuel supply system. The design of standard Solex carburetors has outlet pipes designed to supply gasoline to the mixture formation chamber. By pouring low-grade fuel, thin channels can become clogged, preventing its free passage.
Usually, the channel of the first chamber is clogged. If the engine jerks during a set of revolutions, and after reaching 2500-3000 rpm, the acceleration goes smoothly - the trouble is here.
The defect is eliminated by blowing the unit with compressed air with preliminary cleaning of the nozzles (just in case).
It is also necessary to check the main pump (the sore of all the classics), and the ignition moment.
When you press the gas, a car with an injection engine jerks
If the VAZ 2110 injector twitches, the search for the problem should start from the MRV, PDZ, ECU sensors. In this case, faulty sensors can give a false signal to the control unit, which is the primary source of trouble.
The next reason is clogged nozzles. Symptoms usually appear 15-20 km later after filling low-quality fuel into an empty tank.
The last moment is failure, ignition interruptions. Candles, armored wires are diagnosed.
When you press the gas, the diesel car jerks
Regarding the diesel engine, the solution to the problem is extremely simple - jamming of the moving blades of the main pump. The reason for this phenomenon is considered to be a long idle time for transport in a damp place. It is moisture that oxidizes metal surfaces, which leads to the structure jamming.Elimination of damage is performed by replacing the damaged part.
conclusions
Regardless of the specified primary sources, the main problem of breakdown is the human factor. To prevent problems with the car, it is necessary to timely undergo service procedures, inspections and use only high-quality consumables.
