Car Jerks When Accelerating: 15 Reasons Why

A vehicle suddenly hesitating signifies lots of things. It could relate to the ABS, U-joint slack, or brake issues. It could even be as specific as a faulty IAC valve. But when a car shakes when accelerating, it is primarily due to problems with the ignition system, sensors, or air-fuel intake.

The triggers of this problem are almost endless. But in this article, we will cover some of the top reasons why your car shakes when accelerating.

1. Blocked or dirty fuel injectors
2. Bad fuel injection system, pump, or filter
3. Fuel line damage
4. Unclean or polluted air filters
5. Worn or filthy accelerator cable
6. Plugged catalytic converter
7. Bad spark plugs or ignition coils
8. Failing motor windings
9. Moisture buildup under the hood or distributor cap
10. Faulty carburetors
11. Defective Transmission Control Module
12. Faulty Mass Airflow (MAF) Sensor
13. Tire misalignment
14. Broken cylinders
15. Driver skill

Why does your car jerk while driving? Keep reading to find out why in this article.

15 Reasons Why Your Car Jerks When Accelerating

1. Blocked or Dirty Fuel Injectors

For your vehicle to perform seamlessly, it requires consistent air and fuel intake – the amounts of which should be up to spec. Especially for fuel, sufficient amounts can only be ascertained if there is no perforation or obstruction in the lines that carry the fuel from the tank to the injectors and finally to the cylinders in the engine. So naturally, problems are expected if the said conditions are not met.

While there are many components to an engine, fuel injectors are, by far, the biggest compromise to continuous fuel intake and often cause a car to jerk when accelerating. Any clog or dirt in the fuel lines is the reason why the latter absorbs unwanted moisture, then carries over to the fuel injectors. Eventually, this occurrence will impede the latter’s ability to deliver adequate fuel to the engine on time.

Apart from juddering, dirty fuel injectors also cause loss of power, stuttering, and irregular shaking when pulling from a stop due to frequent engine misfires. Cleaning the injectors helps solve these issues and should be done regularly to prevent recurring problems.

Examine the condition of the fuel injectors while at it, as even the best aftermarket cleaners will not work if the injectors are too spoiled with carbon deposits.

At this point, you may need special equipment like AUTOOL Ultrasonic Fuel Injector Cleaner (view on Amazon) to ensure optimal cleaning or have the injectors replaced if carbon buildup is severe.

2. Bad Fuel Injection System, Pump, or Filter

Now, if it is not the injectors at fault, there is a big chance either the fuel pump or fuel filter is. The reason I say this is that a car jerking while accelerating is often a result of a fuel supply issue.

If the injectors check out (meaning they are not plugged or in bad condition), odds are only one of the other components is causing fuel delivery to be inconsistent. Between the two, I would prefer a bad fuel filter as it is cheaper to replace or fix versus a fuel pump (view on Amazon).

3. Fuel Line Damage

If the fuel system components mentioned above are without fault, it would be worth looking into your car’s fuel pipes to see if they have leaks or are chewed off by rats. These metal pipes are responsible for fuel delivery to the engine while creating needed pressure alongside the fuel pump.

If they become perforated or broken, the required fuel pressure will not be achieved even if the pump is fine, causing bad idling and juddering of your car. Worse, broken fuel pipes can result in your engine blowing up and your vehicle catching fire.

4. Unclean or Polluted Air Filters

As established earlier, your car requires consistent, contaminant-free air intake as much as it does a steady and up-to-spec fuel flow to work. If the air entering your engine is not clean, problems similar to when your vehicle does not get sufficient fuel arise. When this happens, fouled air filters are often to blame – and rightfully so.

Air filters are your vehicle’s first line of defense against dirt, airborne particles, and other pollutants. That said, it is important that they are kept clean to function properly.

The moment an air filter becomes clogged, it will inadvertently allow some particles to get into the engine, adversely affecting fuel combustion and resulting in car jerks when accelerating at low speeds.

Customarily, air filters need to be changed every 12 months or between 10,000 and 45,000 miles – adhering to this interval should keep your air filters in healthy working condition. But depending on many factors (including the type of vehicle you have), you may need to replace or service them more frequently than suggested by the OEM.

5. Worn or Filthy Accelerator Cable

An accelerator cable (a.k.a. mechanical throttle cable) is the component in your engine control system that links the gas pedal to the engine throttle plate. When the former is depressed, the said cable pulls the throttle plate and allows for more fuel to make acceleration possible – hence, its name.

This component is an unlikely cause for car jerking in more recent vehicle makes since modern cars have replaced this component with drive-by-wire electronic throttle controls. However, the reverse is true if your four-wheeler is an early 2000 model (or older).

It is natural for accelerator cables to wear out over time when used. However, its usual five-year lifespan can become shorter depending on driving frequency and duration (not to mention bad driving habits). Pressing on the gas pedal inadequately or too many times are only some of the behaviors that can cause this cable to wear down, fray, or fail completely.

Thankfully, a damaged accelerator cable is one of the more economical and easier things to address on this list. Even before you experience car shakes when accelerating, you will know that something is wrong with your throttle cable if one of the following occurs:

• Your cruise control suddenly malfunctions
• You get a slow acceleration response
• You notice damage to its outer covering during visual inspection

In any of these situations, I highly recommend seeking help from a mechanic and replacing the worn cable immediately to prevent your vehicle from breaking down when you least expect it.

Note: In the case of dirty accelerator cables, exercise extra caution when cleaning them. Overcleaning or using the wrong cleaning products when tidying throttle cables in old cars reportedly leads to high RPM when idling.

6. Plugged Catalytic Converter

Since correct air and fuel intake is crucial to vehicle performance, it naturally follows that proper combustion is too. And this is where the catalytic converter plays a big role. Aside from reducing the pollutants exiting your car exhaust, this component is also responsible for regulating the combustion process inside your vehicle.

A good catalytic converter improves fuel efficiency and power output. Conversely, an obstructed one answers the question, “Why is my car jerking when I give it gas?”

Causes

If you are wondering what causes a catalytic converter to become clogged, here are some of them (they also result in starting problems, hard shifting, and reduced engine power when left unattended):

• Coolant leaks
• Defective spark plugs
• An incorrect air-fuel mixture or car running too rich
• Incorrect timing
• Lack of engine tune-up (car does not get the boost its systems need)
• Malfunctioning O2 sensor
• Misfiring spark plugs (also leads to a meltdown of the ceramic catalyst material in worse scenarios)
• Making only short trips (hinders the catalytic converter from completely burning away hydrocarbons)
• Unburned fuel, engine oil, or antifreeze entering the exhaust system

In some situations, a catalytic converter can unclog itself (light particles in the catalytic honeycomb can disintegrate) when a car is driven for more than 20 minutes. But if the accumulated carbon inside the catalytic converter cells is too much, self-correction will not be possible.

So at the first sign of a clogged cat, make sure to determine the level of blockage right away. If it is not obstructed completely, use a good cleaning solution. Otherwise, consult a mechanic to diagnose the component and see if you require a cat replacement like Walker Exhaust CalCat Carb 81756 Direct Fit Catalytic Converter (view on Amazon).

Tip: For more experienced vehicle owners or those who are mechanically savvy, test your car exhaust for back pressure buildup. You may also use an OBD-II scanner to see if you get any of these fault codes – P0420 to P0424 and P0430 to P0434).

7. Bad Spark Plugs or Ignition Coils

Proper combustion is fundamental to your vehicle’s performance and the reason correct air-fuel mixture is necessary. But it will not happen (no matter how perfect your air and fuel intake is) if there is nothing to ignite and start the burning process. This is where the part played by spark plugs and ignition coils become extremely important.

Unfortunately, it is easy to neglect the condition of these components – partly because they are out of sight. Often, car owners only take time to examine their plugs and the entire ignition system the moment their car jerks when accelerating or when affronted with other similar problems. These relevant challenges include poor fuel economy, misfiring, starting issues, unstable idling, and loud engine noises.

Spark plugs are generally easy to replace or fix, but it is quite the opposite for ignition coils. Replacing the latter can be challenging on some vehicles, especially if the owner is not knowledgeable about their car’s electricals.

Accessibility and sticking components are the most common obstacles pertaining to changing them. Unless you have replaced ignition coils before, driving to your local mechanic or the nearest service center to get things sorted out would be best.

8. Failing Motor Windings

Motor windings “are conductive wires wrapped around a magnetic core” that help drive rotors in an electric motor (especially triple-phase types). They are typically made of copper and used in transformers, generators, and the like.

These windings are essential to vehicles since they help bring the latter to life. However, having an overstressed engine and doing hard acceleration most of the time can cause these wires to fail and the vehicle to jerk.

If you suspect your motor windings as the culprit behind those car jerks when accelerating, test them for resistance and power using an Ohm meter or multimeter like Klein Tools ET600 Multimeter (view on Amazon).

How to Test

For guidance, refer to the steps below. Your owner’s manual should help when it comes to these things:

1. Check the motor’s bearings for wear and tear, as worn-out bearings take away from the motor’s efficiency.
2. Inspect the windings for wear and tear, as well as for resistance and continuity.
3. Set the Ohm/multimeter to read Ohms. Then disconnect the spindle motor from all power sources.
4. Next, test the wires (including T1, T2, T3, and ground wire) and terminals – “short-to-ground in the circuit and open or shorts in the windings.”
5. Test the wires for power (refer to your service manual for values specific to your vehicle).
6. If the spindle motor test fails, verify the problem is not with the connector having coolant on it and interfering with the results. Double-check by drying the connector and retesting.
7. If the results are still failing, check your inserts for burn marks. The presence of these burn marks warrants the replacement of the inserts.
8. Check for wear and tear where the cable moves through tracking.
9. Lastly, visually inspect the motor’s fan. Ensure it is in good shape, not clogged, and can rotate freely.

9. Moisture Buildup Under the Hood or Distributor Cap

This root cause is mainly attributed to cold weather and outside/overnight parking. When you park your vehicle on the street (for instance), condensation that forms under your car’s hood or distributor cap can get inside the engine and cause misfiring and car jerking when accelerating at low speeds.

A one-off occurrence should not automatically be cause for concern, as the condensation evaporates completely after driving for some time. However, it starts becoming a problem when moisture buildup happens too often to the point of taxing your engine.

You can avoid this issue by parking your vehicle inside your garage or in a protected location (preferably warm). But if vehicle shelter is not an option, using a multi-layered EVA car protector (view on Amazon) can help reduce the risk of moisture buildup, especially if you anticipate colder weather.

Also, note that not all vehicles will have this issue. If you have a fairly new model, it may have a coil-on-plug setup and not the traditional one some vehicles have. In this case, rule this item out as the problem source.

10. Faulty Carburetors

There is a good reason why carb rebuilds are popular in online forums and publications. Without question, carburetors are integral to engine and vehicle operation. They handle a car’s air-fuel mixture and impact the engine’s fuel combustion efficiency. And when compromised, it can instigate several vehicular problems – car jerking when accelerating being one of them.

11. Defective Transmission Control Module

If you ever wondered, “Why does my car jerk when I accelerate?” it could be due to your Transmission Control Module or TCM. As its name implies, this module “monitors your acceleration and detects a need to shift gears” during appropriate points in your driving. It oversees how your transmission operates and ensures that it does so according to spec.

Several things can cause your car’s TCM to fail. Off the top of my head, the most common reasons would be voltage overload and faulty wiring. And while these grounds can easily cause your vehicle to jerk, I would not immediately jump to that conclusion.

Quick or abrupt acceleration can cause delays in shifting, which could lead to those little car jerks you experience. Simply put, it is not always your TCM at fault. Nor does it mean that your TCM is automatically defective.

The reverse would be true if you notice your vehicle jerking around when you change gears, as this scenario indicates a faulty TCM or solenoid. Given that the Transmission Control Module is responsible for gear changes when accelerating, delayed or unpredictable shifting is a sure-fire sign that something is wrong with this component (especially if your car is automatic).

12. Faulty Mass Airflow (MAF) Sensor

Issues with MAF sensors are one of the problem sources of car jerking where the CEL also gets activated. As out-of-spec air intake is communicated to the PCM, the latter triggers the warning light while instructing fuel injectors to compensate for the lack of airflow with fuel delivery.

As a result, the car surges forward when accelerating or driving at highway speeds. That said, an illuminated CEL is typically present when MAF sensors go bad – although confirming this is the case via an OBD-II scanner is still best.

Faulty MAF sensors do more than just trigger car jerking. They also send wrong information to the ECU, disrupt air-fuel mixture, increase fuel consumption, and cause other issues such as sluggish performance, rough idling, and stalling. You can prevent MAF sensors from going bad by cleaning them. However, some situations may call for a sensor replacement.

13. Tire Misalignment

Sometimes, slow car movement can be misunderstood as car jerking. This scenario usually happens when one or more tires are misaligned. Tire misalignment (resulting from insufficient tire pressure or a recent on-road accident) consequently leads to your car’s failure to react to pulling. And when this happens, it may behave in a way that would seem like it was bucking forward.

Having your car inspected for alignment immediately after rotating tires or hearing strange noises eliminates car jerking. More importantly, it lessens the likelihood of incurring suspension or powertrain damage.

14. Broken Cylinders

Engine cylinders are where combustion happens in your power mill, making them a critical part of your car’s engine. These components are responsible for controlling the speed of the piston and compression. Sadly, issues like bad ignition coils, lack of spark, and air-fuel mixture running too rich can cause these cylinders to break and fail altogether.

Misfiring and jerking are early warning signs of compromised cylinders – they should be promptly addressed so as not to escalate to severe engine damage and more costly repairs.

15. Driver Skill

Even in this day and age, a large number of consumers still drive cars with stick shifts. There is nothing wrong with it – except that car jerking is bound to happen, especially if the driver is a newbie.

I have no intention to generalize nouveau drivers. It is just that learning how to shift on this type of car is more complicated than if someone were to learn on an automatic gearbox.

The jerking usually happens when a beginner shifts from neutral to 1st gear or continues after a pause while accelerating uphill. It eventually goes away as the driver gains more experience and confidence. Once a learner improves his driving skills and gets used to the controls in a manual transmission, car jerking when accelerating is less likely to occur.

When it comes to more experienced drivers, car jerking can still happen if they misuse the clutch and go ham on the accelerator pedal after. It could be unintentional. But if it were not, the best way to prevent surging forward is by going easy on the clutch and gas pedal and pairing these actions with proper timing.

Conclusion – Car Jerks When Accelerating

To summarize, here are 15 of the most common reasons behind a car jerking when accelerating:

1. Blocked or dirty fuel injectors
2. Bad fuel injection system, pump, or filter
3. Fuel line damage
4. Unclean or polluted air filters
5. Worn or filthy accelerator cable
6. Plugged catalytic converter
7. Bad spark plugs or ignition coils
8. Failing motor windings
9. Moisture buildup under the hood or distributor cap
10. Faulty carburetors
11. Defective Transmission Control Module
12. Faulty Mass Airflow (MAF) Sensor
13. Tire misalignment
14. Broken cylinders
15. Driver skill

Regular upkeep, visual inspection of different components, and intentional driving are some ways to stop a car from jerking sporadically. Likewise, knowing the ins and outs of a vehicle gives owners like you the advantage come handling unforeseen situations.

Because most of what triggers car jerking are imbalances in fuel, air intake, and ignition, it would be wise to always keep these systems in check. But should you find yourself in a bind, it would not hurt to ask a professional for help.