Why Your Automatic Car Jerks When Speeding Up At Low Speeds

Written by

CarParts.com Research Team

Automotive and Tech Writers

Updated on November 6th, 2024

Reading Time: 4 minutes
Summary
  • Some Hyundai vehicles with a gasoline direct injection engine and automatic transmission can jerk when accelerating at lower speeds.
  • The possible causes for the jerking movement include carbon deposits on intake valves, issues with the spark plugs, and dual-clutch transmission problems.
  • You can fix the issue by cleaning the dirty intake valves with a gasoline direct injection cleaner or replacing any bad spark plugs.

Do you own a Hyundai model with a gasoline direct injection engine and automatic transmission, such as the Santa Fe, Sonata, or Tucson? Some owners have reported that their vehicle jerks sharply when they shift from park to drive and step on the gas pedal. Their Hyundai acts like it’s running on fumes, even though the gas tank is full. The issue happens more often when you run the A/C.

What are the possible causes of this issue? Can you fix the problem that causes your car to jerk when speeding up from low speeds?

Why Your Car Jerks When Accelerating at Low Speeds Despite Its Automatic Transmission

Here are some reasons why your Hyundai is jerking when you accelerate from relatively slow speeds:

Carbon Deposits on Intake Valves

The most likely reason for this problem is carbon deposits on the intake valves that admit air into the engine. The deposits interfere with the airflow required for combustion, leading to incomplete burning that can cause your vehicle to jerk at low speeds.

Carbon deposits appear when the engine fails to burn all the fuel in its combustion chamber. The unburnt carbon becomes black soot that sticks to the surface of the intake valves and other internal engine parts. The carbon hardens when it cools, and the deposit grows as more unburned fuel adheres to it.

Earlier engine models are less likely to deposit unburned carbon on their intake valves. Their fuel injectors spray gasoline into their intake manifold. The fuel mixes with the air before passing through the engine cylinders at timed intervals. Once the air-fuel mixture reaches the spark plugs, an electric spark ignites the fuel mixture.

These engine designs allow fuel to flow over the intake valves. Most gasoline products contain additives that can remove carbon deposits from surfaces. When the fuel washes over the valves, it cleans the dirty engine parts and restores the latter’s performance.

Carbon deposits pose a bigger problem for modern engines with advanced technologies like emissions control and direct injection systems. In particular, Hyundai gasoline direct injection engines are prone to having their air intakes coated and clogged by unburned fuel.

A Hyundai gasoline direct injection engine uses a high-pressure fuel injection system that sprays gasoline directly into its combustion chamber. This burns fuel more completely and efficiently, increasing the engine power and reducing emission levels.

Unlike older engine designs, gasoline direct injection engines don’t spray fuel over the intake valves. Since the additives in the gasoline never reach the valves, they don’t get a chance to clean the parts. Without the cleaning effect of the additives, the carbon deposits on the intake valves continue to build up.

Excessive carbon deposits can reduce the engine’s efficiency, resulting in issues like reduced power. They can damage the engine and cause components to fail.

When you run your Hyundai’s gasoline direct injection engine at high RPMs, carbon deposits on the intake valves can break away. Your vehicle might jerk violently in response to the changes.

Incorrect Spark Plugs

Did you recently replace the spark plugs in your vehicle’s ignition system? Check the new ignition parts to see if they’re the right ones for your Hyundai.

Installing the wrong parts will cause problems. Putting incorrect spark plugs can cause issues like your Hyundai jerking at low speeds when trying to speed up.

Cracked and Shorted Spark Plugs

You might have confirmed that the spark plugs are correct, but don’t lower your guard just yet. Check each plug for fractures. A cracked spark plug can short to ground, causing problems with fuel ignition that might affect combustion. It might even make your car jerk during acceleration after being driven at low speeds.

Dual-Clutch Transmission Issues

Some Hyundai vehicles use a dual-clutch transmission. If your car or SUV has this transmission type and jerks while accelerating at low speed, there might be a problem with the complicated system.

A dual-clutch transmission contains two separate transmissions that operate in concert. Usually, one transmission contains the even-numbered gears while the other one has the odd-numbered gears. Each transmission also has a clutch.

Since dual-clutch transmissions are complex and have many moving parts, they’re more likely to develop issues, including jerking at low speeds.

While driving your Hyundai, try to get a feel for the jerks that happen at low speed. Do the jerks feel like shuddering? And do they fade away when your vehicle picks up speed? If you answered yes to those questions, there’s a problem with the dual-clutch transmission.

Thousands of happy customers choose CarParts.com. Shop Now

Tips For Fixing This Problem

No one wants their vehicle to jerk or shudder without warning. It’s unpleasant at best and potentially dangerous at worst. Fortunately, you can usually take steps to eliminate this problem

Here are some tips to prevent your Hyundai from jerking when accelerating at low speeds:

Clean the Dirty Intake Valves

Since the gasoline direct injection engine can’t wash its intake valves, you must clean the dirty part yourself. Get a gasoline direct injection cleaner (also called an intake valve cleaner) and follow the instructions on how to use it.

Replace the Bad Spark Plug

Whether you put the wrong spark plug or have a cracked one, you must replace the faulty part. Ensure the replacement spark plug is compatible with your vehicle and doesn’t have any fractures or damage.

When your car jerks when accelerating at low speeds, your automatic response should be to find out what’s wrong. You can take steps to fix the problem and enjoy safe driving once more.

Written By CarParts.com Research Team

Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.