Throttle Body Cleaning

Bad Throttle Body: Symptoms, Causes & Fixes

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The throttle is one of the essential car components that regulate the strength of an engine; they do this by dictating the amount of air and fuel that the engine can take in. Old cars use one throttle, but modern-day vehicles have more than one throttle for enhanced performance.

Some of the symptoms you will experience if you have a bad throttle body are: engine stalling or won’t start, problems with accelerating and engine light come on. If you want your vehicle to move faster, you would usually push your foot against the acceleration pedal. When you do this, the throttle position sensor will read how much acceleration you desire. It thereafter transmits the information to the vehicle’s computer system. This computer system then instructs the fuel ingestion center on how much fuel and air to take in. 

However, the throttle frame can go bad and begin to affect the functioning of the various parts of the car, including the engine. When this happens, you will need to take immediate action to rectify the bad throttle body problem.

In this article, you will learn the symptoms of a bad throttle body as well as the causes and procedures to fix the problem once you notice it.

What is the Throttle Body?

In the car engine, between the intake manifold and the air cleaner, there is a valve through which fresh air gets to the engine. This valve is what we call a throttle body. Combustion cannot take place in the combustion chambers without the throttle body. The throttle has control over how much passes through to the engine.

If the valve closes, the amount of air that gets to the engine reduces and so combustion is not complete. However, an open valve will let necessary fresh air gets into the engine. This will allow the engine to roar and produced the required sound that will power the car.

The interesting thing about the throttle body is that a car owner or mechanic can control how wide the throttle body opens or closes. With a foot air (gas) pedal, you will be able to control the openings and closing of the butterfly valve of the throttle body.

This description only applies to modern-day cars. Older cars don’t have the electronic sensor that informs the onboard computer system the amount of fuel to release to mix with the incoming air for a proper air-fuel mix ratio.

Usually, throttle bodies are made of a metal-cased tube; a throttle plate joined to the position sensor, an air control valve, and a throttle linkage. The tube ends in a throttle plate which regulates fluid flow. 

Symptoms of a Bad Throttle Body

If you are experiencing any of the following, then there is a good chance that your vehicle’s throttle body has a problem. You’ll need to replace it.

  • The engine refuses to start or stalls

If when you press the gas pedal, the engine refuses to start, stalls, misfires, or jerks then you ought to check it out before the damage becomes unamendable.

  • The Car doesn’t Accelerate

If the throttle body has some faults, the car will suddenly speed up while you drive. Otherwise, the car will hesitate to speed up? Does it speed up but lacks sufficient power? These are all indicative of a bad throttle.

  • The Engine’s Check Light comes on

If the check engine light comes on, this also shows that your throttle has problems. But endeavor to confirm the other symptoms even if the check engine light doesn’t come on. Pay close attention to the other symptoms that follow.

  • The car accelerates but refuses to shift up

A loss of power behavior regularly accompanies this symptom. Here your car accelerates but will not go above 35 miles per hour. This symptom only reveals that the throttle is restricting the amount of torque you are requesting for. 

Causes of a Bad Throttle Body

A throttle may not work properly for any of the following reasons.

  • Dirt, grime, and carbon deposits within its casing

Dirt and grime can build up in the casing and hinder the necessary fluid flow. Carbon deposits can also hinder the atomization of fuel by creating an irregular surface inside the walls of the throttle body.

  • Electrical problems

In the throttle body, when there is a disruption in electrical transmission, inaccurate information is sent to the vehicle’s computer system, and this brings about errors in amounts of fluid taken in and utilized. 

  • Leaky Vacuums

Vacuum leaks can introduce errors into the throttle, and this eventually leads to a malfunction.

  • Poor or high idle

If you are having a vacuum leak problem, there would also be a high idle due to too much air in the vehicle’s system. When put together all these symptoms would only reduce engine performance. 

How to Fix a Bad Throttle Body & Cost?

Tools needed:

Screwdriver, cotton swabs, socket wrenches, household oil, toothbrush (or any soft cleaning brush), paper towels, eye protector, throttle (not carburetor) cleaner, flashlight, rubber gloves, and paper towels


  • Do not smoke while fixing the throttle body
  • Wear eye protection and rubber gloves 
  • Use the flashlight to ensure proper cleaning 
  • Be careful not to destroy other sensitive components of the vehicle, including the gasket and electrical parts.  
  • Depending on the type of throttle body that comes with your car, you may need to employ the services of a technician to remove the throttle body. 


  • Park your car in a garage or safe place and disconnect the battery terminals. With the screwdriver or a gentle pull and twist, remove the throttle-fastened air duct or hoses to have access to the throttle body. Label the ducts as they lead to the nozzle, using a masking tape.
  • After exposing the throttle body, spray the system with the throttle cleaner as it sits inside the air duct. After this, use the soft toothbrush to remove the dirt and carbon deposit on the throttle body. Use the paper towel to wipe the residue left on the part.
  • Placing a small drop of oil on a cotton swab, lubricate the throttle shafts before replacing the throttle body duct. Clean up all parts where the oil may spill.
  • Replace and reinstall the throttle duct, tighten the hose, and ensure you secure the throttle body duct in place. 
  • Reinstall all components, including the battery terminals, and take a test run. Allow the engine to idle for a few minutes after the initial rough idle or stumble. The engine should start normally and the car will be back to its normal state. 
  • With this in mind, you could spend about $500 USD on repair if your throttle body is easily accessible. If the throttle is hidden or requires a lot of energy to access it toiling to get it dismantled then you could pay as much as $1000 USD to repair it.  

Final thoughts

In any given driving situation, the throttle plays a great role in determining your vehicle’s efficiency. Take steps to follow this guide if you want your throttle to serve you for a long time. Don’t forget to look at the throttle body when doing your full car service.

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