Although the vehicle usually warns of possible breakdowns through the different indicator lights on the dashboard, it may also happen that some of them become evident by other means, such as when the car jerks while driving.
It is important to pay special attention to the circumstances under which the vehicle has this problem (engine revolutions, speed, etc.), as this information makes it easier for the workshop technician to diagnose the fault.
Possible causes of the car jerking
When a car jerks, the causes can be diverse. The most relevant are listed below:
1. Fuel injection abnormalities.
It is possible that the vehicle has this effect because there are faults in the injection system. Its causes can be several: injectors in poor condition (worn or clogged), flow control valve or faulty injection pump, etc.
Of the above, the most common cause of injection system failure is a problem with the injectors. In this situation, it is advisable not to circulate with the vehicle to prevent the breakdown from worsening, since a seized injector can lead to damage to other expensive engine components, such as the catalytic converter or the cylinders. In this case, the vehicle could stop and give off a fuel smell.
2. Bad EGR valve.
Anomalies in the EGR valve can cause the car to jerk (in this case, in addition, other symptoms such as the Engine Management warning light come on, lack of power in the vehicle, difficulty in starting, and excessive consumption made out of fuel).
The most common causes of EGR valve failure are electrical defects or dirt accumulated on the valve (residual carbon from the exhaust gases themselves and from the engine lubricant). LOCTITE SF 7235 Cleaner, primarily intended for brake system cleaning, is equally ideal for removing carbon from injector systems.
The EGR valve is responsible for recirculating part of the exhaust gases towards the intake to reduce the harmful emissions that the vehicle expels. Therefore, it is important to address this fault as soon as possible.
The solution is simple and consists of cleaning the valve using specialized products that allow the engine’s performance to be restored.
3. Electrical defects in coils, spark plugs, accelerator pedal, ECU, etc.
Sometimes the passage of time, sudden changes in temperature in different components, humidity, etc. They can cause electrical breakdowns that result in the car jerking while driving. Among the most common consequences of this failure is poor contact in the ignition coils, a faulty spark plug, an electrical defect in the accelerator pedal, or abnormalities in the ECU.
When an electrical connection is damaged, it tends to sulfate and cause conductivity failures. Unless the connection is very deteriorated and requires replacement, there is the option of cleaning it with specialized products such as LOCTITE SF 7039. This product, in addition to cleaning the damage, covers the surface of the wiring with a waterproof layer that protects it from oxidation.
4. Catalyst in bad condition.
The catalyst can fail as a result of a primary failure in some component related to it, although the most common is that the problem is due to the obstruction of the catalyst itself. A clogged catalyst implies that the mesh that retains the combustion particles is plugged and prevents the exit of gases. These gases accumulate and leave irregularly and intermittently, generating these jerks. In addition, there is a risk that the smoke outlet is clogged and the engine is damaged by the backward movement of the gases.
5. Wrong or bad fuel.
Detecting a wrong refueling early can prevent a major breakdown. If you have recently refueled and you notice small jerks in the car, it is advisable to take this symptom as an alarm signal and check, with the help of a specialized technician, if the refueled fuel is the ideal one. If not, it must be removed and the necessary actions must be taken to avoid possible further damage.
In the case of a gasoline vehicle to which diesel has been added, in addition to emptying and cleaning the tank, it is also necessary to clean the pipes and replace the fuel filter. In an extreme case, the catalyst could also be affected.
On the other hand, if a diesel vehicle has refueled gasoline, in addition to emptying and cleaning the tank, it is also necessary to clean the pipes and replace the fuel filter. In an extreme case, the injectors and injection pump could also be damaged.
6. Filters clogged (air, fuel, etc).
Correct vehicle maintenance is essential to extend the useful life of the engine. Driving with the filters in poor condition can be a problem when a car jerks while driving, has starting difficulties, failure of flow meters, etc.
The jerks, in this case, are due to clogging of the filter due to excessive accumulated dirt, which does not allow free circulation of fuel or air.
7. Anomalies in the gearbox.
If the gearbox does not connect properly with the engine, jerks can occur at certain speeds. The main reasons are usually the poor condition of the torque converter of the automatic transmission or the wear of the clutch discs. Both causes cause internal gearbox slippage. Unless jerks are accompanied by blows, this fault can be remedied by replacing the gearbox oil.
8. Carbon build-up in the exhaust gas recirculation system.
The carbon accumulated in the exhaust gas circuit (on the walls and in different components of the circuit) causes the gases to jam, which can lead to jerks while the vehicle is running. Another possible symptom of this problem is puffs of black smoke coming out of the exhaust. A solution to this failure is to disassemble all components and clean them with a general-purpose parts cleaner such as LOCTITE SF 7063 or with high degreasing power brake cleaners such as LOCTITE SF 7235.
9. Flowmeter in bad condition.
The air mass meter, flowmeter, or flowmeter measures the mass of air entering the intake manifold from the outside. If the air filter is contaminated, it can affect the flow meter operation, causing the vehicle to jerk or lose power. In these situations, it is usual for the Engine Management warning light on the instrument panel to come on. To solve this fault, it is necessary to renew the engine air filter and the flow meter.
10. Bad engine butterfly.
The butterfly regulates the flow of air entering the engine to fill the cylinders quickly and efficiently and thus achieve optimal combustion. When the engine throttle fails, there is too little or too much air in the cylinders, causing the car to jerk, lose power, and consume more fuel. On some occasions, this fault can be remedied by cleaning the component with a general-purpose parts cleaner such as LOCTITE SF 7063, and on others, the throttle must be renewed. Use LOCTITE SF 7235 to remove accumulated carbon or dirt from the butterfly valve.
Although there is a multitude of breakdowns that can cause this symptom, the 10 points mentioned previously are some of the most common problems when a car jerks. To prevent this type of failure, it is essential to respect the manufacturer’s maintenance tables and periodically carry out a general check of the vehicle using a diagnostic machine and visual examination. Only in this way can these types of problems be prevented and optimal vehicle operation achieved.