In this article, we will discuss the common problems that can cause Kia and Hyundai vehicles to not accelerate. In one situation, a Kia was only accelerating to about 15 mph and would not go any faster.

Problem

Kia or Hyundai vehicles may fail to accelerate due to problems with the throttle position switch. When the driver presses the gas pedal, the maximum speed that the car can reach is about 10 or 15 mph. Some symptoms include that the engine has no power when you press the gas pedal or that the RPMs will not go past 2000.

The first warning that you may get is the check engine light will come on. Soon after you may notice that the engine or vehicle speed does not increase when you press the gas pedal. It is common as well for this issue to be intermittent at the early stages.

It is easy to misdiagnose this problem as an engine misfire. Thus changing the spark plugs is not going to solve the problem if the issues are caused by a faulty throttle position sensor. You may also wonder if the car is out of gas. That's why it is important to read the CEL

Common Causes

Throttle Position Switch

The most common issue that can your vehicle not to accelerate is a faulty throttle position switch, also referred to as the TPS. The Throttle Position Sensor is a potentiometer that controls the throttle valve. Check with the dealer to see if they have an updated position switch.

Replacing the TPS at the dealership can cost around $400-$600 USD depending on your location and model. Replacement TPS for Kia and Hyundai can also be purchased online. 

Catalytic Converter

A bad catalytic converter can also cause your Kia / Hyundai not to accelerate.

Typically you can get to speeds over 50mph when the catalytic converter is defective, but it may take a while for the car to get up to that speed.

When the catalytic converter gets clogged it creates excessive backpressure, and thus the vehicle loses power. You can have a muffler shop perform a backpressure exhaust test on your vehicle.

This will confirm if the catalytic converter is defective or not. Replacing cat converters can be expensive. They can cost close to $1,000 if you want an OEM catalytic converter but aftermarket units cost only $200-$300 USD at a muffler shop.

How to diagnose

Several fault codes may be present when the vehicle fails to accelerate. You can use an OBD2 scanner reader to retrieve the codes from your car.

Here is the list of codes that were triggered by a defective TPS.

• P0123 - Throttle Position Sensor/Switch A Circuit High Input

• P0222 - OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input

• P2101 - Throttle Actuator Control Motor Circuit Range/Performance

How to replace Throttle Position Sensor

1. Open the hood.
2. Disconnect the negative battery terminal.
3. Locate the electronic throttle body. The throttle body is mounted on the intake manifold assembly.
4. Remove the air intake hose.
5. Disconnect the electrical connector from the TPS.
6. Remove the 4 bolts on the TPS using a 10 mm socket.
7. Reinstall in reverse order. Tighten the bolts to 11.5 Nm.