6 Telltale Symptoms of a Bad Throttle Body (+ How to Fix)

Ever found yourself driving down the road, only for your car to stumble or hesitate for no apparent reason?
Or
Do you find your fuel gauge dropping faster than normal?

Your car might be trying to tell you about a problem with the throttle body.
Buckle up as we uncover the symptoms of a bad throttle body and how to keep your car running smoothly.

Let’s go!

6 Key Symptoms of a Bad Throttle Body

Your car may indicate a faulty throttle body through several signs, like engine stalling, increased fuel consumption, etc., as covered below.

1. Rough Idling

Carbon buildup in the throttle body can affect airflow, leading to a rough idle.

In modern cars, the Engine Control Module (ECM) uses the Electronic Throttle Body (ETB) to let in air as the engine idles. So, carbon deposits and grime buildup on the ETB can lead to rough idling.

In older vehicles, carbon deposits can build on the Idle Air Control Valve (IACV) mounted on the throttle body, causing a rough idle.

2. Engine Stalling

A dirty throttle body reduces the air entering the engine, disrupting the air-fuel mixture. This can make it difficult for the engine to maintain the idle speed and eventually stall.

More worryingly, your car may also stall while driving if a bad throttle body or a faulty throttle position sensor (TPS) doesn’t let in the required amount of air.

3. Illuminated Check Engine Light

If the throttle valve doesn’t move expectedly, the throttle position sensor sends an error signal to the ECM, triggering the Check Engine Light. A failing throttle body can also trigger the Electronic Power Control dashboard light on Volkswagen Group vehicles. Your car may also enter “limp mode.”

Note: Limp mode results in reduced power delivered to the vehicle, helping avoid engine damage due to driving with a fault.

4. Acceleration Issues

Grime and carbon buildup inside the throttle body can affect the throttle valve movement. If the throttle valve gets stuck, it may lead to sluggish acceleration or an unintended acceleration response.

5. Poor Fuel Economy

A faulty or dirty throttle body can lead to poor fuel economy by impacting the relationship between the gas pedal and the throttle position. A bad throttle body may restrict airflow, leading to a rich air fuel mixture and poor engine performance.

6. Engine Misfire

Though an engine misfire generally occurs due to spark plug or fuel injector problems, a bad throttle body can also cause it. As the throttle body controls the air flow entering the engine, problems with it can throw the air-fuel ratio off balance, triggering misfires and reduced engine performance.

You’ll get a Check Engine Light and misfire codes for all cylinders instead of a specific one, as the throttle flap controls the airflow to all cylinders.

Now, let’s see how you can address a throttle body problem.

How to Fix a Bad Throttle Body

Depending on the condition of the throttle body, your mechanic may clean or replace it.

A. Throttle Body Cleaning

Here’s what a mechanic would do to clean a throttle body:

Disconnect the negative battery terminal.
Remove the air intake hose from the throttle body.
Disconnect the electrical connector for the throttle position sensor from the throttle body.
Remove the throttle body from the intake manifold.
Spray throttle body cleaner on the throttle plate and inside the throttle body.
Clean the inside of the throttle body.
Reinstall the throttle body.
Reconnect the air intake hose and the throttle position sensor.
Reconnect the negative battery terminal.
Start the vehicle and perform a throttle reset.

B. Throttle Body Replacement

The mechanic will replace the throttle body on your car if:

They can’t clean it properly.
The throttle flap, throttle shaft, or the mechanical linkages to the throttle cable are damaged.
The electronic throttle actuator is faulty.
There is a damaged throttle body or TP sensor electrical connector.

Additionally, it’d be a good idea to get your car’s throttle and fuel delivery system inspected for the following:

A faulty throttle position sensor
Gas pedal sensor problems
Intake manifold pressure sensor issues
A clogged air filter
A bad mass airflow sensor (MAF sensor)
A failing fuel pump
A malfunctioning fuel injector
A defective fuel pressure regulator

These parts can cause problems similar to bad throttle body symptoms.

Coming up next are the reasons behind a faulty throttle body.

What Causes Throttle Body Problems?

A throttle body issue can arise from:

1. Carbon Buildup

Carbon buildup can occur when gases from the crankcase, containing oil vapors and exhaust gases, condense on the cooler throttle body. These gases enter the air intake system through the Positive Crankcase Ventilation (PCV) valve.

2. Electrical Issues

Problems with the throttle valve actuator on an electronic throttle body can cause it to malfunction. Corrosion in the electrical connector can also lead to a bad throttle position sensor.

Have more questions about the throttle body?
Let’s answer them.

4 FAQs about the Throttle Body

Here are answers to common queries you may have about the throttle body:

1. What Does a Throttle Body Do?

The throttle body sits between the air filter and intake manifold and houses the throttle plate or valve. A small throttle shaft in the throttle body lets the valve rotate on its axis. This controls the air entering the engine based on the input from the accelerator pedal.

The ECM monitors the movement of the throttle valve using the throttle position sensor mounted on the throttle body. It also uses readings from the throttle position sensor and the MAF sensor to control the fuel injection into the engine.

2. Can You Drive with Bad Throttle Body Symptoms?

No, you shouldn’t drive with signs of a damaged throttle body, as it can lead to acceleration-related issues and reduced power. This can compromise your safety on the road, lower fuel economy, and harm your vehicle.

Get your car inspected by a mechanic soon after you notice the symptoms of a failing throttle body.

3. How Much Does a Throttle Body Replacement Cost?

The average throttle body replacement cost is between $500 and $650, with the part priced between $400 to $550 and the labor charges ranging between $90 and $110. The actual cost of replacing a throttle body will depend on your car’s make, model, and year.

4. Could a Faulty Throttle Position Sensor Be the Problem?

The throttle position sensor monitors the throttle valve’s position, which adjusts based on the accelerator pedal input. When you accelerate, it signals the Engine Control Unit (ECU) to open the throttle valve, increasing airflow into the engine.

That’s why a faulty TPS can display many of the same symptoms as a faulty throttle body, such as rough idling, poor engine performance, and an activated check engine light.

However, a faulty TPS should display some nuances that can help differentiate the two components:

Cruise control issue
Transmission issues in automatic vehicles
Specific diagnostic codes, such as P0122

Driving with a bad TPS is never recommended. Instead, the best thing to do is call a mobile mechanic. Driving with a bad TPS isn’t just risky; it can also lead to expensive engine repairs.

Resolve Throttle Body Issues with AutoNation Mobile Service

Your engine won’t run with a malfunctioning throttle body, or you’ll experience poor engine performance, fuel economy, and other issues.

Noticing early symptoms?
Have your car inspected by an expert mechanic at AutoNation Mobile Service. We’re a mobile auto repair and maintenance service capable of sorting out your faulty throttle body from your driveway.

We also offer a 12-month, 12,000-mile warranty on all repairs.

Contact us, and our mechanics will have your car running like new!