Symptoms of a Bad or Failing Throttle Body

When we talk about the factors that control the strength of an engine, the very first thing that comes to … Continued

When we talk about the factors that control the strength of an engine, the very first thing that comes to mind is the throttle.  A throttle governs the fluid (fuel + air) flow of an engine. Airflow plays a vital role in an engine’s performance. Although traditional vehicle engines comprise of a single throttle body, many powerful contemporary vehicles comprise more than one throttle body, which operates coherently and results in much greater power.

A typical throttle body comprises a metal casing. The metal casing has a large tube dissecting through the middle of it. This tube is blocked by the throttle plate. The primary control on airflow is governed by the throttle plate. However, there might be additional valves for air to flow as well such as an idle air control valve.

A typical throttle body also includes a throttle position sensor, which is usually located adjacent to the throttle linkage, inside the main casing of the throttle body. The location of the throttle position sensor allows it to be mechanically connected to the throttle plate.

In some cases, the throttle body is connected directly to a mass air flow sensor. However, sometime the mass air flow sensors might be located near the air filter box instead.

So how do tell if you have a fault in your engine’s throttle body? The first symptom which you will immediately pick is an irregular response of the engine on pressing the gas pedal. Delays in engine response and unexplainable jerks and stalling are common symptoms of a faulty throttle body. The key is to be able to identify the fault before the damage is irreparable.

Although there is always a possibility for a mechanical failure of the throttle body, it is even more common for one or more of the auxiliary components of the throttle body to go bad. This includes various sensors attached to the throttle body and are not exactly part of the throttle body itself.

Identifying the specific model of a throttle body component can seldom be quite a challenge. Information such as the vehicle year, make and model is sometimes not enough. If you are stuck in such a situation, you can search for the component using its Original Equipment Manufacturer (OEM) number.

failing throttle body

Main Component of a Throttle Body – Throttle Plate

We often confuse the gas pedal as being the primary component of the throttle. Whereas this is not the case. When you press the car’s accelerator, the engine generates power and speed by the injection of more fuel into the engine. The accelerator pedal in this case only acts as a linking mechanism to the throttle body. The throttle body itself is a tubular component of an air intake system which responds to the pressing of the gas pedal. The throttle body is commonly situated between the intake manifold and air filter.

The largest component of the throttle body, which regulates the airflow, is the throttle plate. The angle of the throttle plate controls the airflow to the combustion chamber. This along with the quantity of fuel injection and the timing of the ignition determine the engine torque.  The plate is connected to the accelerator pedal with a cable connected to a set of linkages. When the accelerator pedal is pressed, it causes rotation of the throttle plate. In the case of electronic throttle control, this mechanism is controlled electronically, while it also determines the input for other engine components, such as the engine coolant sensor.

Periodic preventive maintenance and cleaning of the throttle plate are essential if your engine has been in running for around 70,000 – 80,000 miles. Specialized throttle body cleaning sprays are commonly available in the market. Moreover, The adjustment of a throttle plate is essential to configure the amount of airflow during engine idle time.

In case your throttle plates are completely worn out you will need to consider replacement of the old throttle plates with new ones.

Throttle Body Temperature Sensor

Temperature plays a vital role in an engine’s overall performance. An important component of the throttle body is the throttle body temperature sensor. This sensor is designed to monitor the temperature of the fluids and air entering the fuel injection system of an engine, or in other words, the fuel temperature.

The combustion of fuel involves decomposition (atomization) and vaporization of fuel and air molecules. Monitoring and controlling the temperature is critical to makes this chemical process more efficient. The fuel particles should be small enough such that they have a larger surface area so that the fuel is subjected to more heat.

A sensor for throttle body temperature is expected to wear out over time. Periodic checks by a mechanic will prevent any undesirable situation. In case there is a fault in the sensor it should be immediately replaced by a professional mechanic.

Coking – a common problem

A frequently identified problem after constant use of an engine is commonly referred to as coking. This problem occurs when black residue starts to accumulate on the throttle plate or inside the throttle body.

The most common preventive maintenance advised to avoid coking is periodic cleaning of the throttle plate bore. If the residue is thick, you may require additional solvents for cleaning, such as a carburetor cleaner. You need to be very careful while cleaning the throttle body as could even cause further damage to the throttle body if you are too harsh.

Throttle Position (TP) Sensor

The Throttle Position (TP) sensor is typically included in the body. It is bounded by a magnetic collar. When the throttle shaft is rotated, the magnetic collar induces a flux in the magnetic field. The magnetic pulse is received by an integrated circuit (IC) which transforms the magnetic pulses into electrical signals and determines the actual position of the throttle valve.

Naturally, without a proper signal, your engine performance is bound to deteriorate. The proper functionality of the Throttle Position Sensor is vital for achieving the optimum power and fuel efficiency from an engine. The most method used by mechanics to test the functionality of a Throttle Position Sensor is with the help of a digital multimeter.

Common symptoms of a faulty TP Sensor include delayed acceleration, erratic stalling of the engine and abrupt increase or decrease in vehicle speed.

symptoms of a failing throttle body

Throttle Cable

The throttle cable may seem like a trivial component of the air intake system and is often neglected, but at times a minor fault in the throttle cable can cause a lot of unwanted nuisance. Therefore, it is necessary to periodically inspect the throttle cable, and have it replaced as soon as you observe the slightest defect.

The throttle cable is the link between the heart and mind of a driver and his machine. Worn-out and damaged throttle cables can lead to unsafe driving conditions and deteriorate engine performance. Therefore, the throttle cable should be inspected periodically for any visual defect. Rusting, bends or cuts can create weak points in the cable and are immediate causes of concern. Therefore, systematically inspect the cable from end to end to the best of your visual ability.

Following steps should be followed to replace a throttle cable:

  1. Wear protective gloves and safety glasses
  2. Locate the throttle cable with the help of a manual
  3. Disconnect the throttle cable from both ends. This is normally achieved by either pushing the throttle bracket and sliding out the cable from a dedicated hole, or by removing a small clip with the help of a screwdriver.
  4. Pull out the old throttle cable from the engine compartment.
  5. Pull the new throttle cable from the engine compartment into the car interior
  6. Install the new cable

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.

Electronic Throttle Control (ETC)

Unlike conventional vehicles which comprise of a mechanical linkage between the accelerator pedal and the throttle body, In the case of hybrid electric vehicles, when a driver presses the accelerator pedal, the response does not go directly to the engine. Instead, a request for power is sent to an energy management system (EMS) that works independently from the engine control unit (ECU) of the vehicle. Subsequently, the energy management system determines the amount of power to be generated by the throttle body.

The electronic throttle control makes a significant contribution towards improving the driver’s performance. It provides smoother transitions between changing gears and also compensates for the abrupt changes in torque associated with rapid accelerations and decelerations.

The Electronic Throttle Control provides a platform that can cater latest driving features such as cruise control, traction control and stability control. Essentially, these features require torque management which is provided by the Electronic Throttle Control.


  1. Symptoms of a Bad or Failing Throttle Body – Your Mechanic
  2. When does a throttle body need to be serviced? – Testing Autos