Why is My Car Jerking? - All Possible Reasons
A car that jerks when accelerating, when starting the engine or even while driving at constant speed is showing symptoms of a problem. There can be many causes behind this jerking motion, including problems in the starting system, fuel supply, engine or the exhaust pipe. You may even notice your car engine light has come on to warn you of an issue. Jerking movements while driving can be very dangerous, leading not only to vehicle damage, but also the potential for serious road accidents.
Getting to the problem at the first symptoms can avoid more serious break-downs. In oneHOWTO we'd like to give you some advice so you know all the possible reasons and answer the question: why is my car jerking?
- Car jerking caused by a blocked catalytic converter
- Jerking caused by a faulty spark plug
- Car jerking because of a worn accelerator cable
- Car jerking because of dirty injectors
- Car jerking because of the motor winding
- Dirty engine causing the car to jerk
- Other reasons your car is jerking
- The car is pulling
Car jerking caused by a blocked catalytic converter
Car jerking can be caused by a blocked catalytic converter. The converter regulates toxic gas emissions given off as part of the combustion process. When a catalytic converter is blocked, the result is that gases are not being ejected as they should be. If your car has a blocked catalyst, you will also notice the following symptoms apart from the jerking.
- The 'Check engine' light will turn on
- Your car jerks when accelerating
- The car's fuel efficiency will have dropped
A blocked catalytic converter is one of the most common reasons why a car jerks while accelerating. This is because the gas emissions caused by newly combusted fuel get backed up. When you put your foot down on the accelerator pedal, you are adding more fuel to the system and putting more pressure on the converter. The car will likely delay its response and then be followed by a sudden jerk or lunge forward.
One of the most common reasons for a clogged catalytic converter is actually due to problems elsewhere in the car. Fuel, oil or other fluid might be leaking into the device from another part of the engine. Leaded gas is also a common culprit, although this is fortunately becoming less available. A leaky exhaust valve might also lead to the introduction of unburned gas into the catalytic converter. The result is overheating which can also cause the car to jerk while accelerating.
Unfortunately, replacing a catalytic converter can often be an expensive task. It is important you know that a clogged converter is the actual problem as replacing it can cost a lot of money and effort. You can check out our article on the symptoms of a blocked catalytic converter to help you know, but we recommend consulting a trusted mechanic to be on the safe side.
Jerking caused by a faulty spark plug
Another cause for a car jerking can also be a fault in the spark plug or one of its cables. You will know this is the case if your car jerks when you start it in the morning. The symptoms are very similar to a blocked catalyst, but if it's a problem with a spark plug, you should also notice the following:
- The engine will make even more noise than it usually does, like that of an airplane.
- Car jerks when accelerating but also when you start the ignition.
The spark plug is used in combustion engines to convert electrical energy from the battery into a literal spark which lights the aerated fuel. Since the spark needs to set the fuel alight, the fuel will come in contact with the end of the spark plug. A dirty spark plug means that the park can't light and the fuel in the cylinder doesn't ignite. If the spark plug or the electrical cable to it is faulty, then the same thing happens.
Of course, if the fuel can't become ignited, then the car won't start. The reason why your car is jerking during ignition is because a car has as many spark plugs as it does fuel cylinders. Some of them may work, but the ones which don't cause the car to jerk. This is one reason why you should change all your spark plugs at the ame time, even if some have a little life in them yet.
If dirt or grime is the problem, then you may not need to change the spark plugs. Rather, you can clean them to avoid the car jerking. This will likely only be a temporary solution.
Car jerking because of a worn accelerator cable
A car jerking can also be a result of the accelerator cable being worn out. This is the cable which connects the throttle (accelerator pedal) with the fuel control. The more you push down on the throttle, the more tension put on the cable and the more fuel is added to the engine. If you put more fuel into the engine, the care will go faster.
However, if the cable is worn out, then the tension exerted will not be as even. It may even tense, then slacken due to the wear. This is what will lead to the car jerking. Apart from the jerking, there are other signs your accelerator cable may be worn or in some other way faulty:
- Your car takes extra time to respond when you press the accelerator.
- If you take a look inside, you will also notice that the outer covering of the accelerator cable is damaged.
If your accelerator cable is worn out, the best thing you can do is replace it as soon as possible. If you do not, there is a risk of the cable snapping. If this happens in transit, it can lead to a very serious accident as you will lose all power to your engine. If you are unsure of how to do this, then you will need to speak to a mechanic. However, if you consider yourself well-versed in car mechanics, you can try adjusting the accelerator cable yourself.
Car jerking because of dirty injectors
A car engine is a complicated set of systems. Fuel is sent round these systems to be burned and create propulsion. Burning fuel has many unhealthy byproducts, often leading to dirt and grime also getting around the engine. If this dirt gets on the fuel injector, it can lead to jerking movements while driving.
The vast majority of cars produced after the 1980's use fuel injection engines. These inject fuel into the combustion chamber to mix with air and be ignited by the spark plugs. If the fuel injector in one or more of the cylinders is dirty, it can cause the car to jerk when pressure is placed on the throttle. However, since fuel is continuously being injected into the engine, this is not the only time it might jerk.
If your car is jerking due to dirty fuel injectors, you may also observe:
- Your car also loses power.
- Your engine misfires frequently and stutters or jerks while driving at constant speed.
Dirty fuel injectors are not the most problematic reason for your car to be jerking. However, they may be an indirect cause of other problems in the engine. It's best to clean them regularly to avoid costly repairs down the line. You can do this yourself using a specific cleaning kit, which are quite cheap and can be found at most garages.
Car jerking because of the motor winding
The car's engine/motor winding can be another reason for car jerking. The winding is the wrapping of wires for electric engines. This winding needs to be wrapped in the correct way for the specific engine. If the windings are not correctly in place, it can lead to wear. Wear can also occur due to simple usage over time. However, wear of the engine's winding is most likely caused by the engine being put under stress - i.e. through hard acceleration.
If your windings are faulty, there are two possible outcomes for the engine:
- If your car has more than one winding, but one is broken, the car will likely jerk.
- In the case there's only one winding, the car will not start.
The only way of knowing if this is the case is through the use of an Ohm meter. You can purchase them at most mechanic's garages or hardware stores. However, if you are unsure what to look for, it's best you check with a mechanic. They will also be better able to diagnose the problem, in case there is another reason why your car is jerking.
Dirty engine causing the car to jerk
As you can see by many of the options, the main causes of a car jerking are wear and dirt. If your car is old or has been used in particularly dirty conditions, then it is understandable the engine will become correspondingly dirty. However, there are some specific engine parts you should take a look at the ensure it is kept running smooth.
If your fuel filter gets clogged, it can lead to other parts of the engine accumulating waste. To ensure this does not happen, you should find out how to tell if your fuel filter is bad. This is something you can do on your own if you know what you are doing. However, if you don't clean and refit it properly, it can be very dangerous, so you should take the car to a qualified mechanic.
Other reasons your car is jerking
While wear and dirt are common reasons why your car jerks while driving, there are some less common reasons for this occurrence. They include:
- Stick shift: if you are used to driving an automatic car, then you may have problems driving stick. A stick shift requires you to change between gears yourself as you accelerate. This can be difficult for the uninitiated, especially if driving an old or unfamiliar car. The car may jerk as a result of awkward gear changing.
- A new part: while we all hope the mechanics we entrust our cars to are top notch, it is possible they have not done as good a job as they should. For example, if your car is jerking after a rack and pinion steering change, then the jerking may be due to a faulty installation. Bring the car to another mechanic (preferably one recommended by a trusted friend) and get them to check the work.
- Sudden unintended acceleration: your car may jerk due to something known as sudden unintended acceleration. This can be due to a mechanical or electrical error. It might also me due to misapplication of the pedals or if there is a problem with the pedal alignment. However, in very rare occasions, there is a fault with the model of car. This is something which can lead to an entire line of models being recalled. You can check to see if there is a recall on your particular vehicle as it may be the cause of jerking.
If you are unable to diagnose the problem yourself, take the vehicle to a mechanic. When your car is jerking while breaking, there are also some specific reasons you may want to investigate.
The car is pulling
As a final note, it is important to be sure your car is actually jerking. It might be possible your car is actually reacting to pulling. This happens at a slower pace to jerking as it occurs more gradually. If this is the case, there may be a problem with your car's alignment, tire pressure or the tire rotation system. To better understand, take a look at all the possible reasons your car is pulling to rule it out.
If you want to read similar articles to Why is My Car Jerking? - All Possible Reasons, we recommend you visit our Car Maintenance and Repair category.