Symptoms of a Bad or Failing Throttle Body

In today’s modern fuel injected cars, the throttle body is a critical piece of the air intake system that controls the amount of air flowing into the engine. The amount of air allowed in depends on how far the driver presses the accelerator pedal to the floor. As you press down on the pedal, the throttle position sensor receives a signal relative to where your foot is, ranging from all the way up (zero acceleration) to all the way down (full acceleration). This sensor relays the information to the car’s main computer — giving it constant updates as to the position of the throttle. The computer knows what to tell the fuel injection system in terms of how much more or less fuel to inject into the system based on the position of the pedal.

When this process is regulated properly, a perfect balance of air and fuel is introduced to your car’s engine, allowing it to run smoothly and perform at an optimum level. Here are 5 signs of a failing throttle body:

1.Grime Buildup

Dirt and grime can build up inside the housing, this being known as coking, and causing an interruption in air-fuel flow. As a result of not having an ordinarily smooth surface for the fuel and air to flow through, this delicate mixture is interrupted by a rough surface that causes an imbalance in the flow. Similar to dirt and grime, carbon deposits can create an uneven surface inside the walls of the throttle body, which can disrupt the atomization of the air-fuel mixture.

2. Electrical Problems

Electrical connection problems can cause inaccurate or intermittent information to be relayed to the car’s computer. As with any electrical connection, connectivity issues can cause a wide variety of unpredictable signals to be transmitted. In the case of the throttle body (and related sensor), when this happens it causes false information to be relayed to the car’s computer, resulting in faulty corrections to the air-fuel mixture. You may notice a switch into “limp-home” mode, where power to the car’s engine power is reduced and throttle operation is limited.

3. Airflow Disruptions from Vacuum Leaks or Throttle Stop

Vacuum leaks can disrupt the air-fuel flow because of an imbalanced airflow, which can cause throttle body pressure problems. The issue could also be an incorrectly adjusted throttle stop. This is a component that acts as a gate-keeper and establishes a minimum or maximum position for a throttle body plate to be opened or closed. A maladjusted stop wouldn’t allow in the correct amounts of air and fuel.

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.

5. Check engine light

The check engine light can indicate many issues within a car including a faulty throttle body. In more modern cars, an electronic throttle control (ETC) constantly monitors throttle body performance. Any problem detected with it will turn on the check engine light.

As a part of your regular service intervals, include the air induction service and fuel injection flush to clean out any carbon deposits and dirt. You will need to have the check engine light shut off by a qualified mechanic. This will include scanning your car’s computer system for fault codes to indicate problems with your fuel injection system and specifically throttle body components. These will give the mechanic an indicator as to what to check for and how to repair the problems.


Next Step

Schedule Vehicle Engine Mechanical Inspection

The most popular service booked by readers of this article is Vehicle Engine Mechanical Inspection. Once the problem has been diagnosed, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. YourMechanic’s technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews... LEARN MORE

SEE PRICING & SCHEDULING

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Recent Vehicle Engine Mechanical Inspection reviews

Excellent Rating

(149,537)

Rating Summary
140,027
5,194
1,055
749
2,512
140,027
5,194
1,055
749
2,512

Raymond

37 years of experience
222 reviews
Raymond
37 years of experience
Cadillac Brougham - Vehicle Engine Mechanical - Las Vegas, Nevada
Talent and passion for what you do in any field is critical, Raymond seems to have both. I have dealt with many Mechanics in my day Raymond is one of the best. Thank you sir.
Ford Probe - Alternator - Las Vegas, Nevada
Arrived on time and quickly swapped out the part. Excellent work.

Patrick

33 years of experience
1254 reviews
Patrick
33 years of experience
Mini Cooper - Oil Change - Austin, Texas
This is the 2nd time Patrick has provided my MINI service & I couldn't be happier.
Infiniti G37 - Oil Change - Austin, Texas
Patrick’s always great and has been for a few years now. He’s always on time and thorough I know my car is in good hands with him.

Robert

31 years of experience
610 reviews
Robert
31 years of experience
Mazda 6 - Pre-purchase Car Inspection - Santa Clara, California
I bought a used car after Robert's thorough pre-purchase inspection report and recommendations. He understood that I am new to cars and did a great job to make sure it is a great buy. Highly recommended!
Acura MDX - Timing Belt - Saratoga, California
We have known Robert for many years & know of his skills

Jason

17 years of experience
429 reviews
Jason
17 years of experience
Honda CR-V - Oil Change - Redwood City, California
Informative and friendly!
BMW 328i - Brake Pads Replacement (Front) - Palo Alto, California
Extremely helpful

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

Related articles

How to Replace a Car Throttle Cable
Throttle cables link the accelerator pedal to the throttle plate. This cable opens the throttle and lets air into the engine for acceleration.
3 Essential Things to Know About Your Car’s Gear Shifter
The The gear shifter allows the vehicle to be put into different gears on a manual transmission. In an automatic transmission, the gear shifter is known as a gear selector. The gear shifter is normally located between the two front...
How Long Does a Throttle Body Last?
There There are so many components involved in a vehicle running properly, but some of the main ones are rather basic in their role. The throttle body is one of those parts. This component is part of the air intake...

Related questions

What causes the truck not to go?

Hi and thanks for contacting YourMechanic. Check the throttle position sensor (TPS) for voltage and resistance. There should be a 5 volt reference voltage to the sensor with a ground. There should be a resistance on the sensor. If there...

How do I put my truck in gear?

There are many gears that your truck can be shifted into. These gears tell the car whether to drive, stay still, or move. To put your vehicle into gear. Hold down the brake pedal. Start the vehicle. Move the...

Rough idling, hard shifting and shuddering at the highway

Thanks for writing in about your 2002 Isuzu Trooper. The rough idle may be due to the fuel injection system being dirty or having an engine vacuum leak causing a lean condition. The hard shifting and shuttering with the chirping...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com