6 Symptoms of a Bad Throttle Body You Should Know (+ the Fix)

You know something’s up when you see the tachometer needle swinging while your car idles. Sometimes, the RPMs drop too low, and the engine stalls.

In such cases, it’s possible you have a throttle body problem.
But can you continue driving?

Let’s explore the symptoms of a bad throttle body and what the issue means for your car.

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 the airflow through it, 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 on the ETB can lead to rough idling. Whereas, in older vehicles, the Idle Air Control Valve (IACV) mounted on the throttle body can get carbon deposits and cause a rough idle.

2. Engine Stalling

A dirty throttle body allows lesser airflow than required at a given throttle position (throttle valve angle) to sustain the idle engine speed. This could cause the engine to stall. Your car may also stall while driving as you press the accelerator pedal if the throttle position 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 (TP sensor) sends an error signal to the ECM, triggering the Check Engine Light. Additionally, a failing throttle body can 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

In the case of a dirty throttle body, the throttle position may be as per the gas pedal input, but the airflow would be lower than required. This can result in a rich air-fuel mixture, leading to poor fuel economy.

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 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

Get your car inspected by a qualified mechanic, like the ones at RepairSmith, if you suspect throttle body problems. 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:

It can’t be cleaned 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:

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 deposits can result from the crankcase gases containing oil vapors and exhaust gases condensing on the relatively 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. A corroded electrical connector for the throttle position sensor may also cause a fault.

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

3 FAQs about the Throttle Body

Here are answers to common questions you may have about the throttle body.

1. What Does a Throttle Body Do?

The throttle body is located 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 amount of 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 I 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, reduce 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?

A throttle body replacement can cost you between $180 to $895, with the part priced between $130 to $670 and the labor charges going from $50 to $225. The actual cost of replacing a throttle body will depend on the make, model, and manufacturing year of your car and the labor charges.

Wrapping Up

Your car’s engine can’t run without a functional throttle body, and you’ll experience engine performance, fuel economy, and other issues if the part is faulty.

Noticing early symptoms of a throttle body issue?
Get your car inspected immediately by an expert mechanic at RepairSmith to ensure your safety and prevent further damage to your vehicle. We’re a mobile auto repair service that can fix a bad throttle body and other issues right in your driveway.