Symptoms Of A Bad Throttle Body And Replacement Cost

Do you suspect that your car has a bad throttle body? Here are all the symptoms of a bad throttle body and the estimated replacement cost.

A throttle body is the mechanical extension of your foot and the accelerator pedal.

When something goes wrong, it’s the equivalent of a permanent lead foot or disconnecting the pedal entirely. These are both extreme hazards, meaning you should go straight to your local mechanic.

In this guide, I will explain the main symptoms of a bad throttle body and what might be going wrong.

Table of ContentsShow

What Is A Throttle Body?

cleaning throttle body

A throttle body is a vital part of all internal combustion engines.

It sits between the air filter and the intake manifolds, controlling how much air enters the combustion chambers. This means you can manually adjust how fast the engine revolves (rpm) and, in turn, the vehicle speed.

A throttle body houses the throttle plate, a type of butterfly valve. This opens and closes based on information from a sensor on the pedal. Older cars used mechanical cables and linkages.

The throttle plate opens when you push the accelerator pedal, allowing more air to pass.

When you lift your foot off completely, it almost closes. There’s a small, preset gap to allow the engine to idle.

Signs Of A Bad Throttle Body

Since the throttle body is responsible for how much air enters the engine, any arising problems impact the entire vehicle.

As with any mechanical/electrical component, the throttle body can fail. Most issues boil down to an electrical fault, particulates around the plate, or a seized valve.

Here are some of the main symptoms of a faulty throttle body.

Check Engine Light

car check engine light on

A Check Engine light will most likely illuminate when you have a throttle body problem. The ECU can usually tell that things aren’t adding up.

Whenever a Check Engine light illuminates, head straight to a local mechanic. They’ll use an OBD scanner tool to look for any stored codes.

Relevant OBD II codes might include any of the following:

  • P2107
  • P2108
  • P2111
  • P2112
  • P2118
  • P2119

Finding these codes can be a great help. They mean you won’t waste time or money fixing something that isn’t the root problem!

Problems At Idle

Man Calling Mechanic Service After Vehicle Problem

Your engine is most sensitive at idle. That’s such a true statement.

The ECM monitors the engine’s condition at any given moment. The idle speed requires constant minute adjustments – if it drops too low, the engine stalls. Too high, and you’re wasting fuel.

Watch out for any of the following symptoms when your engine is idling:

  • Rough idle – the motor feels like it’s struggling to keep going.
  • Rough idle and stalling – the engine stops and turns off completely. It’s run out of momentum to keep itself going.
  • Higher-than-usual idle speed – a typical car’s idle speed is between 700 and 1,000 rpm.
  • Sudden acceleration – the engine speed suddenly accelerates.
  • Sudden stalling – the engine might have been running fine, then turned off without warning.

The throttle body houses the plate responsible for controlling the airflow. Any problems with it (or the related sensors) could mean the butterfly valve opens or closes too much. It might even get stuck open.

This could lead to any of the above symptoms.

Usually, you’ll see stalling or low revs rather than sudden acceleration. You can keep your engine running by gently holding your foot on the gas pedal.

If your car’s engine unexpectedly speeds up, you might need to switch it off at the key to prevent an accident.

Low Power And Low Top Speed

Driving Car

Low power and top speed could be related to the misfires mentioned below.

You often see these symptoms when driving because there isn’t enough air flowing in. This either imbalances the air/fuel ratio or means less gas/diesel enters the cylinders.

Either way, your engine is low on power.

Misfires

Car spark plug replacement. Repairing of vehicle.

When there’s a massive lack of air, it’ll cause misfires. There might be enough fuel and a working spark plug, but without oxygen, nothing burns.

Expect to find misfires in multiple cylinders unless certain spark plugs/injectors are in worse condition than others.

Sudden Acceleration/Rev Reduction

Close up of the car speed meter. Car speedometer close up, speed 60

Changes in engine speed at idle have been mentioned above.

However, severe throttle body problems could lead to engine speed changes while driving.

This might happen due to the throttle body or its related sensors misinterpreting data from the pedal sensor or ECU. The plate could also stick open or closed.

This is an extremely serious problem, as your car could speed up or slow down outside of your control.

You’ll need to stop and pull over immediately, turning your engine off. Call for breakdown assistance and go straight to the nearest mechanic you trust.

Expert diagnosis from an automotive electrician might be needed.

How Do You Fix A Throttle Body Problem?

Before attempting to fix a throttle body fault, mechanics will check your issue isn’t being caused by something else. For example, the throttle position or accelerator pedal position sensors could have failed.

If you have a throttle body problem, you should try cleaning it first. In many cases, this solves the issue, especially if you see rough idling, low power, and stalling.

You could use an additive to clean out the throttle body. This is the most thorough method, although it’s often somewhat complicated. It also carries certain damage risks.

Most mechanics will choose the more straightforward option: disconnecting the battery, removing the throttle body, and cleaning it with parts cleaner and a rag.

When replaced, you might find the problem has gone away. This could be related to the cleaning process. An electrical glitch could also have reset while disconnecting the battery.

If cleaning and additives don’t work, you might need a new throttle body.

This is a simple job, although the new throttle body might need calibrating. Mechanics will use an expensive scanner tool for this.

Finally, it’s worth checking for ECU glitches. Repairs here will need advanced electrical engineers.

Throttle Body Replacement Cost

Dollars (Price, Cost)

The cost of a throttle body clean should be low. It’ll take mechanics a matter of 15 or 20 minutes.

As such, you can expect to pay $40 or $50 for this service.

It might be determined that you need a new throttle body. In this case, you’ll pay for the part and labor.

A throttle body component is challenging to cost estimate. Depending on your make and model, it’ll cost anywhere from $250 to $700.

You can expect to pay about $125 in labor on top of this. However, remember that mechanics get parts at a trade discount. You might save money by getting this job done professionally!

Throttle Body – Concluding Thoughts

Throttle body problems can be dangerous. As soon as you notice any issues with your engine, go straight to a mechanic.

If you’re lucky, a quick clean will fix everything, and you’ll be on your way again.

Either way, it’s better to stop at an auto shop than stall or crash on the side of the road!

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Benjamin Kitchen

Ben is an automotive author from England. With experience in a fast-fit garage, he's an IMI-qualified light vehicle technician. He aims to help drivers worldwide with common automotive problems. You’ll often find him working with his 1.2 Vauxhall Corsa – it may have a tiny engine, but in eight years it's never once let him down!