Why does the car jerk when accelerating
In addition to discomfort during driving, jerks can lead to a quick failure of various components and assemblies of the car (transmission, suspension, etc.), and to an unsafe situation on the road - for example, when overtaking or climbing a steep hill. It is impossible to ignore such problems, the malfunction must be diagnosed and eliminated immediately.
CAUSES OF JERKS DURING ACCELERATION
The car can twitch during acceleration due to a fairly large range of malfunctions - both individually and in combination. Most often they concern the two most important systems of the car: the fuel and ignition systems, but they are far from being limited. Some problems can be fixed on your own, with others it is better to contact a service station. It is better to start looking for the causes of the problem by increasing complexity.
Clogged filters. First of all, air. Its pollution leads to the re-enrichment of the mixture (lack of air in the air-fuel mixture entering the cylinders), as a result - increased fuel consumption and uneven engine operation. A clogged fuel filter cannot allow fuel to pass through in sufficient volume in an even flow, which negatively affects power and dynamics.
Replacement of air and fuel filters — Subaru Impreza, 1.5 liter, 2001 year on DRIVE2
Poor quality fuel is one of the most common causes of jerks. Bad fuel clogs the filters and the fuel line, does not burn out completely, preventing the engine from developing passport characteristics, leaves carbon deposits in the combustion chamber: on candles, valves, pistons.
The fuel line and fuel pump can also be the culprit when the car's engine does not get enough fuel, which means it will twitch when accelerating. A faulty pump has reduced performance, it does not develop the required pressure, and the fuel lines can become clogged or kinked.
Incorrect operation of the fuel injectors (both on injection gasoline and diesel engines) is another possible cause of jerks during acceleration. Clogged or worn nozzles will result in reduced performance, poor spray quality, delayed firing and rough engine operation.
Problems in the throttle lead to incorrect fuel supply - the reaction of the engine to pressing the pedal seems to be late. The nature of this can be either mechanical - when the damper is dirty or its mechanism breaks, or electronic - in case of a malfunction of the throttle position sensors (in nodes where the drive is implemented by a cable) or the pedal position sensor. The electronic drive of the gas pedal is fraught with additional problems: contacts in the circuit and the need to “prescribe” (or “teach”) the throttle after most manipulations with it: flushing, installing a new unit, removing errors.
Throttle: malfunctions and repair methods
Calibration may also be required by the ECU - the electronic engine control unit. In this case, we are talking not only about updating the car's software (the so-called "filling the firmware"), but also about the competent setting of all control parameters - for example, setting the ignition timing, changing the composition of the fuel mixture, and controlling output parameters.
Failures can also be caused by malfunctions of other electronic sensors - mass air flow, position of the crankshaft and camshaft, detonation, etc. Incorrect data from them, received by the ECU, will lead to an incorrect opening / closing moment of the fuel injectors.
Spark plugs are the first on the "list of suspects" among the components of the ignition system. Systematic skips, poor-quality combustion of fuel in the cylinders lead to uneven engine operation and failures.
Malfunctions of ignition coils, high-voltage wires and a modular unit (if any) - breakdowns, lack of contact, and others - lead to a similar result: the engine starts to triple, run unevenly, twitch during acceleration.
Air leakage in places of depressurization of the engine air duct leads to a depletion of the mixture (that is, an excess of air), which means a drop in power and loss of engine thrust. in addition, when air enters in abnormal places, the computer does not have the ability to correctly determine its amount, which means that it can adequately adjust the fuel supply.
Jerks during acceleration can also occur due to the fault of the transmission: sometimes - clutches for automatic connection of all-wheel drive (AWD or similar systems), and more often - automatic transmission ("kicks" when shifting gears). In addition to external problems associated with the malfunction of the already mentioned throttle sensors and the sensor control unit, the reasons may also lie in the automatic transmission itself: in solenoids, friction clutches, as well as in insufficient oil levels, leading to overheating and insufficient pressure in the box.
In supercharged engines, the turbine can cause jerks: the solenoid valve of the pressure control system or its electric drive.
Other problems with the electrical part - short circuits, caused by
Damaged insulation, poor contact, incomplete latching of connectors can also cause “floating” equipment defects, leading to jerks.
Finally, the cause of uneven operation of the engine, both during acceleration and in other modes, can be damaged (worn out) engine mounts - because of them, the units will be subject to excessive vibrations.
TIPS AND RECOMMENDATIONS
Since the list of possible malfunctions is very large, it is advisable to conduct a comprehensive diagnosis to eliminate all possible factors in order to eliminate problems. Do-it-yourself repairs will not bring the desired result in all cases - on your own, in garage conditions, you can only change consumables (filters, spark plugs and ignition coils) or drain low-quality fuel from the tank, and this may not be enough.
Due to similar symptoms, difficulties can arise both with determining the causes of jerks (especially when there are several of them and they are interconnected), and with the degree of wear. Both for checking and for routine maintenance - for example, for diagnosing fuel pump pressure or flushing injectors - you will need special equipment and qualifications to work with it.
Particularly responsible is the intervention in the "brains" of the car - the ECU - or in the operation of the automatic transmission. The consequences of their unqualified repair can be fatal and lead to immobilization of the car and other costly "results". Therefore, it is easier, and in many cases cheaper, to turn to professionals - specialists from service stations of the Wilgood smart car service network, who always know the answer to even the most difficult questions.