It can be pretty annoying if your car jerks as you accelerate and can be very dangerous, especially when entering a freeway. You need to address the jerkiness of a vehicle immediately to prevent the issue from becoming more serious, but what causes a car to behave that way?
A car jerks while accelerating when the engine is misfiring. Misfiring often occurs when one of the components that supply air or fuel to your engine is malfunctioning or dirty. The most common culprits are faulty fuel injectors, worn-out spark plugs, or a dirty air filter.
Read on to explore what causes a car to jerk while accelerating. This article will cover several potential causes and what you need to do to rectify the issue.
What Causes the Car to Jerk When Accelerating
The most common cause for a car to jerk when accelerating is a fuel or air supply disruption that leads to engine misfiring. An engine misfire is when one or more cylinders fail to produce power due to something as simple as moisture or dirt in one of the engine components.
When you step on the accelerator, you expect the engine to respond by getting you to your desired speed. If the car loses power as this happens, it can cause the vehicle to jerk and disrupt the rate of acceleration. A jerky car is hazardous and a nuisance to drive, so it needs to be fixed as soon as possible.
Let’s examine the probable causes of why a car jerks while accelerating.
Dirty or Faulty Fuel Injectors
The fuel injector is responsible for spraying fuel to the intake manifold for air and fuel to mix. That air-fuel mixture then undergoes compression in the combustion chamber to power the engine.
If a fuel injector is dirty or faulty, it won’t send the right amount of fuel to achieve a balanced air-fuel mixture, causing the engine to misfire. A misfiring engine will cause the car to sputter and affect the rate and consistency of acceleration.
Worn-Out Spark Plugs
Spark plugs are crucial components since they’re responsible for igniting the fuel in each cylinder during the combustion process. In essence, spark plugs create the explosion that powers the engine.
A dirty or worn-out spark plug will fail to create a good spark, which means the fuel in the cylinders won’t ignite at the right time, causing the engine to misfire and experience inconsistent power delivery.
Moisture in the Distributor
A distributor takes care of supplying the spark plugs with a high voltage current from the ignition coil, following a set firing order with precise timing. If you park a car in a cold area for an extended period, moisture can form under the distributor cap.
Moisture can cause the distributor to malfunction, resulting in fuel not igniting at the right time. Poor timing will cause the engine to misfire, resulting in jerking during acceleration at low speeds.
Clogged Catalytic Converter
A catalytic converter turns an engine’s harmful toxins into safe gasses. What sets it apart from the other components is that it doesn’t supply air or fuel to the engine. Instead, a catalytic converter is part of its exhaust system.
A catalytic converter can get clogged by a rich air-fuel mixture or oil that has made its way into the exhaust system. These contaminants can turn into soot and eventually block the airways in a catalytic converter.
Once the airflow in a catalytic converter becomes restricted, it can delay engine responsiveness and cause the car to jerk while accelerating.
You may also like to read: How to Unclog a Catalytic Converter.
Faulty Mass Airflow Sensor
A mass airflow (MAF) sensor is part of a vehicle’s fuel injection system, and it calculates the amount of air entering the engine. It sends that information to the computer so that the fuel injectors can supply the right amount of fuel at the right time for a balanced air-fuel mixture.
Suppose the MAF sensor is contaminated or faulty. In that case, it won’t accurately measure the amount of air entering the engine, and the computer won’t be able to calculate the right amount of fuel the injectors need to supply. A defective MAF sensor will result in poor power delivery, particularly at higher speeds.
Bad Fuel Pump or Fuel Filter
A fuel pump takes care of transferring fuel from the gas tank to the injectors. The fuel filter keeps the fuel running smoothly in the engine and keeps the fuel pump and injectors clean by trapping dirt, rust, and other impurities.
A bad fuel pump will fail to deliver the right amount of fuel to the injectors, leading to a rise in fuel pressure that can cause a car to jerk. The vehicle will also become sluggish to drive and may struggle to rev to the red line.
Perforated Fuel Lines
Fuel travels from the tank to the engine via fuel lines. Most fuel lines are made of rubber and can get damaged or worn out over time.
If one of the fuel lines is punctured, it’ll lose pressure, causing the car to start jerking. You will need to immediately fix a leaking fuel line, as it may cause a fire.
Dirty Air Filter
An air filter keeps dirt, particles, debris, and insects from reaching the engine. It also helps to ensure the engine receives an adequate amount of air to facilitate good performance.
A car needs air just as much as it needs fuel to run, and a dirty air filter may restrict the necessary airflow the engine needs to run smoothly. If the air filter is damaged, it may let particles and dirt into the machine, affecting performance. If the damage is bad enough, it may even cause engine damage.
If your car jerks while accelerating, you should check if the air filter needs to be cleaned or replaced.
Damaged Accelerator Cable
New cars use drive-by-wire technology to transmit how much pressure you put on the accelerator to the car’s throttle body. Older cars use a cable that opens up the throttle as you floor the gas pedal.
The accelerator cable is made of braided metal and can get damaged through constant use. If the cable gets damaged, it’ll affect how the engine responds when you step on the gas pedal since it may not open the throttle plate accordingly, which can cause the car to jerk.
How to Fix a Car Jerking When Accelerating
If your car is jerking every time you put your foot on the gas pedal, don’t immediately rush to a mechanic. The most common causes of jerking are easy to fix with a bit of cleaning, and you can save a lot of money by cleaning your car’s components before running to the shop.
To fix a car jerking while accelerating, you can:
- Clean your fuel injectors
- Clean the spark plugs
- Clear moisture from the distributor
- Clean or replace your air filter
- Clean your mass airflow sensor
To provide more detail on how to address a jerky car, let’s examine the fix for each of the issues one by one.
Clean Your Fuel Injectors
There are several ways to clean your injectors, and some methods are easy enough without the help of a mechanic.
The easiest way to clean your injectors is by using an over-the-counter fuel-injector cleaner. You simply have to pour the cleanser into your gas tank when the fuel is almost empty, then fill the tank up with gas. The cleaner contains additives and detergents to clean the injectors as you drive.
Using a fuel injector cleaner is more suitable as a preventative form of maintenance. You may need to use a fuel injector cleaning kit to deal with clogged injectors. To see the step-by-step instructions on using a fuel injector cleaning kit, watch this YouTube video from Scotty Kilmer.
Clean The Spark Plugs
If your car jerks due to faulty spark plugs, it might be best to replace them. However, you can try to clean the spark plugs to address the issue until you get a new set.
To clean your spark plugs, you’ll need to access them by removing the high tension wires on the cylinder head. It’s advisable to clean the spark plugs one at a time since removing them makes it harder to determine how to put everything back, and there’s a greater tendency for debris or dirt to fall into the plug holes.
Remove the spark plugs using a spark plug socket. The EPAuto spark plug socket (Amazon) can swivel and has a built-in magnet to make removing spark plugs easier.
You can clean the spark plug tip with 220 grit sandpaper or a file for more stubborn deposits. Spraying carb cleaner can help remove the dirt. Wipe the spark plugs dry and use a wire brush to clean the threads before putting them back in.
Clear Moisture From the Distributor
You can deal with moisture in the distributor by parking your car under the sun. However, if you need a more immediate fix, you can also clean the distributor.
To clean a distributor, unscrew and pop the cap open, then use the screwdriver to remove powdery deposits from the contact point. Spray penetrating oil like WD-40 on the tips inside and wipe it dry using a rug or a blower.
Clean or Replace Your Air Filter
If you can’t replace a dirty air filter that’s causing your car to jerk, you can try cleaning it to solve the issue.
You’ll find the air filter housed in a plastic box with a tube leading to your intake manifold. Check your owner’s manual if you have trouble locating it. Once you find the air filter, remove it by releasing the clamps around the box.
You can clean the air filter using a vacuum or a blower to remove dust and loose dirt. If you want to give it a more thorough clean, you can move it back and forth in a bucket of water with a cleaning solution. Be sure that the air filter is completely dry before reinstalling it since it isn’t healthy for an engine to take in water.
Clean Your Mass Airflow Sensor
You can clean your mass airflow sensor for preventative maintenance or address your car’s jerkiness.
The MAF sensor is on your car’s intake and usually sits right after the box that houses your air filter. To remove the MAF sensor, start by unplugging the wiring harness connected to it, then unclamp the airbox where your air filter is. Loosen the hose clamp to detach the airbox and MAF sensor from the air intake tube.
Once removed, you can clean it by spraying a mass airflow sensor cleaner on the metal wire and resistor. Let it dry for about 10 minutes before reinstalling it.
The components of a MAF sensor are sensitive, so don’t use any other cleaner except a mass airflow sensor cleaner.
Issues That Require Professional Help
Unfortunately, you can’t use a DIY approach to fix all the problems that can cause your car to jerk while accelerating.
It’s best to bring your vehicle to an auto repair shop and consult a mechanic if you suspect any of the following faulty components causes your car’s jerkiness:
- Catalytic Converter
- Fuel Pump or Fuel Filter
- Fuel Lines
- Accelerator Cable
Aside from being delicate and hard to reach, the components mentioned above will likely be replaced by a mechanic if they confirm that the parts are defective.
Final Thoughts
A car that jerks while accelerating is both irritating and dangerous to drive, so it’s a problem that you can’t ignore. Various reasons cause a vehicle to jerk, but a jerky car usually indicates a problem with air or fuel supply that leads to an engine misfire.
In many cases, dirty components like spark plugs, fuel injectors, or the air filter are at fault for a misfiring engine, which you can fix without bringing your car to a mechanic. However, if your vehicle still jerks after cleaning everything, taking your vehicle in for repairs may be your only option.
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- By Car Roar