6 Symptoms of a Bad Throttle Body (and Replacement Cost in 2022)

What is a Throttle Body?

The throttle body is the component on your engine that controls how much air enters the engine manifold and to the combustion chamber. It’s a relatively simple component that just opens up to various angles to let the correct amount of air flow in depending on the throttle position.

On older vehicles a mechanical linkage connected the throttle body to the gas pedal, while modern vehicles use sensors to achieve the same result.

Vacuum Leaks

Leakage in the vacuum chamber can cause pressure problems in the throttle body which leads to undesired flow and disturbs the air and fuel mixture. Apart from a vacuum leak, an improperly aligned throttle stop can also result in pressure anomalies. The throttle stop is the part of the throttle body which governs the minimum and maximum position for the throttle body plate to be shut or opened.



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What Does a Throttle Position Sensor Do?

A throttle position sensor is similar to the motor cortex in the human brain, it controls one of the most important components of the car that keeps your engine running like a throttle body. Picture a little module in the car that reads how far down you have pressed the gas pedal. It gathers that information and relates it to the mass airflow sensor and the engine’s RPM to make sure that the correct amount of air/fuel ratio is going into your engine properly.

What is a throttle body?

Mass Airflow SensorAn engine needs two things to stay running which is air and fuel. Normally a car will pick up air through the intake and passes it through the Mass Airflow Sensor. The air will travel up the intake and it will reach your throttle body. The throttle body is a circular valve that’s located in between your air filter and Intake Manifold. In the old days, there was a wire attached to the gas pedal of your car and it would move accordingly to how you pressed it. Nowadays there is an electric system that’s far more efficient than the old ways but it can still have issues.

What happens when my throttle position sensor goes bad

When a TPS goes bad, then the car’s throttle body won’t function properly. It could either stay shut or it won’t close properly which is a severe issue. If it stays shut then your engine is not going receive air and it won’t start. When the throttle gets stuck in an open position than your vehicle will receive too much air and cause it to have a high or fluctuating idle.

What Are The Symptoms and Signs Of a Failing Throttle Position Sensor?

You may not think much about your car’s TPS, but you’ll notice when it starts to go bad.

Lack Of Power

If your engine isn’t getting the fuel it needs, or is getting too much, you’ll notice that it doesn’t seem to be accelerating as it should be. When you put your foot down, the TPS should be screaming out for more fuel, but it won’t if it’s malfunctioning. If the opposite happens, your vehicle may surge forward when you’re not intending to speed up.

Trouble Accelerating

In a similar vein, you may notice that your car will accelerate, but won’t get past a certain speed. It might feel like the car just fizzles out after first or second gear and won’t upshift or go any faster.

Uneven Idle

If your car can’t maintain a constant engine speed when it’s sitting still, your TPS may be on its way out. A constant level of fuel delivery is necessary to maintain a steady idle.

Check Engine Light

On its own, a check engine light can mean absolutely nothing, or can mean something catastrophic is happening. If it’s seen in conjunction with any of the symptoms above, it’s a good indicator of TPS issues.

You might see a check engine light when the TPS starts to fail., Depositphotos

Throttle Body Replacement Cost

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While the throttle body isn’t the most expen

While the throttle body isn’t the most expensive component on your vehicle, it’s not exactly cheap either. If you do find that your vehicle needs a new throttle body, you can expect to spend anywhere between $450 and $600 on both parts and labor.

And if you’re thinking of doing the job yourself, you’re not going to save a ton. That’s because the vast majority of the cost comes from the parts, not the labor. If you plan on doing the job yourself, you can still expect to spend between $400 and $500 for your new throttle body.

Because of the expensive price of parts, it’s a good idea to see if you can’t clean up your existing throttle body and save yourself a few bucks.

4. Poor or High Idle

When a throttle body is not functioning correctly, some noticeable characteristics may be poor or very low idle. This can include stalling when coming to a stop or very low idle after starting, or even stalling if the throttle is quickly pressed — resulting in the throttle body plate opening and closing very quickly.

In the case of a large vacuum leak, you may experience a very high idle because too much air is being allowed into the intake system. All of these symptoms will contribute to poor engine performance and, as a result, will cause your check engine light to come on.

The Drive’s Pro Tips

It’s important to note here that your mileage may vary, depending on the make, model, and year of your vehicle. The TPS in older vehicles may be physically different or located in an odd spot, so it’s best for you to refer to your vehicle’s maintenance manual for pointers. 

We’ll also note that, in some cases, you’ll need to use a voltmeter to adjust the sensor. This can be done with the engine running, but will depend on the requirements of your vehicle, so again – check the manual!

How to Choose Throttle Body Cleaning Products

There are plenty of choices when selecting a throttle body cleaning product. These sprays are formulated to do a difficult job, which means they contain poisonous chemicals and are highly flammable and volatile. Use of these sprays will require safety measures when using the product. When researching for throttle body products, verify that the one you select is specifically designed for cleaning the throttle body and says that on the label or in the directions for use.

Cleaning the Throttle Body

Even if you have an air filter on your car, dirt a

Even if you have an air filter on your car, dirt and soot come from the turbocharger, EGR valve, and the crankcase ventilation and get stuck on the throttle body valve. After a whole, it will cover the valve so much that the RPM will be affected.

A dirty throttle body valve causes many problems with the throttle body; therefore, it is often possible to clean it. To find out more about cleaning it, you can check our guide here: Throttle body cleaning. Do not forget to recalculate the throttle body with a diagnostic scanner afterward, though.

Next Step

Schedule Vehicle Engine Mechanical Inspection

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How to replace throttle position sensor and replacement cost

A vehicle engine needs a predetermined amount of air, just like it needs a predetermined amount of gas. If it doesn’t receive the amount of air necessary for a given moment, it will negatively affect the combustion process. This means lack of engine power and other potential problems. You don’t need to ignore the root of this problem. You need to diagnose the cause of this issue with an automotive scan tool or take your vehicle to your mechanic for a proper check.

If the culprit is proved to be a bad TPS, you have

If the culprit is proved to be a bad TPS, you have to replace it with a high-end sensor. The average cost for a throttle position sensor is estimated to be $89 – $170. The service fee should be $40 – $60, while the parts should be around $49 – $110. However, this is an estimated price and may slightly go above or less our estimation. You can save the service charge by replacing the parts yourself. The replacement process is pretty easy and straightforward.  If you diagnose your vehicle and find any of these error codes, P0120, P0121, P0122, P0123, P0124, P2135,  it means the ECU has detected an issue with TPS. Stay tuned; let me show you how to replace the throttle position sensor.

Things Needed:

  • Flathead screwdriver
  • 100 mm socket (optional)
  • Ratchet handle
  • Throttle position sensor

Disconnect your negative battery terminal and locate the sensor: You need to disconnect the negative battery terminal to prevent any short circuit or to create a fault code to your car computer. Then, locate the TPS; it’s typically mounted on the throttle body.

Remove the Electrical connectors and unscrew the TPS: Gently remove the electrical connectors on the sensor. This electrical connector is pretty easy to remove. You can easily remove it by pressing the tab on it and wiggle it right off. Once you take off the electrical connector, look for fastening bolts or screws holding the TPS, gently loosen and take it off. Remember, always compare old parts and new parts before installation.

Install the new throttle position sensor: After comparing and confirming that both parts are the same, you need to install the new sensor following the reverse process, starting by mounting the TPS and installing the electrical connector. Whenever you removed an electrical connector like the TPS connector, always inspect the connectors for corrosion. Any corrosion between the connectors could cause resistance, and of course, that can cause an issue. Snap the electrical connector in place, and you should hear a distinct clip sound.

Connect the negative battery terminal and cross-check your work: Head on to the battery and ensure the negative terminals are well tightened. Tighten any other components you removed, start the vehicle, and run on idle and acceleration and see if your effort has finally paid off. Depending on your vehicle, like old Ford rangers and Chevrolet Silverado, Tahoe, and Silverado, you may need to adjust the sensor manually. Most Japanese cars automatically adjust to provide peak performance. Watch this video for visual clarification.

How do you test a throttle position sensor?

There are three electrical connectors on the sensor, the ground wire, the variable output, and the +12 volt input. Disconnect the TPS and insert the alligator test lead on the right Jack on the meter. Turn the range switch to 20k ohm scale or 20,000 ohms. Connect the test leads to variable output, TPS ground wire, and the other lead to the +12 bolts.

Now you want to slowly move the butterfly flap in the throttle body from its close range to the full open range while watching the readings on the meter. The reading should move steadily as you move the flap to the open range and decrease steadily as you return it. Any sudden decrease or increase on the readout signifies a lousy TPS and should be replaced.

How do you reset a throttle position sensor?

The easiest and straightforward way of resetting the throttle position sensor is by unplugging the engine control fuse for 5 minutes or removing the negative battery terminal.

Can a throttle position sensor cause transmission problems?

The throttle position sensor monitors the throttle position that is manually controlled by the acceleration pedal. The acceleration pedal is used to determine engine load, and if it fails, it can lead to hard shifting automatic transmission.

How do you know if your throttle body needs cleaning?

The throttle body is a vital system component of your vehicle fuel management. Most issues associated with the throttle body usually need cleaning. And these issues are caused as a result of carbon buildups that require cleaning. If you notice slowed acceleration or stuttering engine, shaky feeling while driving or uneven acceleration, accompanied by an engine warning light, you need to inspect and clean the throttle body.

Should I clean or replace the throttle body?

Generally, throttle bodies need to be cleaned and not replaced entirely. However, you may need to replace specific related system components. Whenever you notice erratic idling, engine hesitation, or any related sign of a lousy throttle body, always inspect the MAF sensor to ensure it’s working correctly, as it could be the root cause of erratic idling and engine hesitation.


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