Diagnosing and cleaning a faulty throttle body

To always maintain an optimal air-fuel ratio, a faulty throttle body can cause issues. Diagnosing and cleaning it is essential.

Role and development

The throttle body is designed to regulate the air intake into the engine to achieve an optimal air-fuel ratio for combustion. It complements the injection system, which manages the supply of petrol and/or diesel.

These two components have long replaced an older mechanism (carburettor) that simultaneously supplied air and fuel.

With the advancement of mechanics and anti-pollution standards, the carburettor system quickly showed its limitations.

Injectors were then invented, offering much greater precision in delivering the required amounts of fuel. This led to the creation of a specific part for air regulation: the throttle body.

Operation

For proper functioning, the throttle body and the injection system must be coordinated. A sensor (or a cable for older vehicles) is located at the accelerator pedal to measure the pressure applied to it.

This data is then transmitted to the engine control unit, which manages the throttle body opening and fuel injection, also considering other information received from the lambda sensor and the air flow meter.

To better control air intake, the throttle body is located just after the air flow meter and air filter.

Its operation is quite simple: it is a movable flap system that opens and closes to control the air flow.

Faulty throttle body: risks

Like other mechanical parts, the throttle body can become clogged due to the accumulation of dirt in the air, making it defective.

Since it is located after the air flow meter and air filter, this often indicates poor air filtration and consequently a clogged sensor at the air flow meter. This clogging usually results from the failure of these two components.

Overall, the risk is having a poor air-fuel ratio, which can eventually damage several mechanical parts such as the EGR valve or the catalytic converter.

Additionally, a faulty throttle body will also lead to increased fuel consumption and, consequently, more pollution. This is a reason for a failed vehicle inspection!

Faulty throttle body

Symptoms

As you might expect, it is not easy to associate specific symptoms with a faulty throttle body…

Vehicle consumption could be an indicator, but it could also point to issues with other mechanical parts. The same goes for the engine warning light, which can illuminate for various reasons…

Jerks during acceleration, a sudden loss of speed, or even the engine stalling are more significant indicators, although it remains difficult to link them directly to a throttle body failure.

You can first test your accelerator sensor to determine if the issue originates there.

Performing a car diagnostic

The best solution to confirm a faulty throttle body is to perform a car diagnostic. With our klavkarr diagnostic tools, you can read and clear various engine and transmission fault codes.

Here, the returned fault code is P0120, which corresponds to a problem with the throttle circuit or the accelerator pedal, significantly narrowing down your search! :)

You then need to check them to identify which one is defective.

Cleaning the throttle body

If your throttle body is defective, it is likely clogged. In this case, depending on the vehicle model, it may be possible to clean it yourself.

You can find tutorials on forums and YouTube tailored to different car models.

Generally, it will take no more than an hour. You will need basic tools (screwdrivers, wrenches) for disassembly, a small brush (like a toothbrush), and a can of penetrating oil with a small tube for precise application.

I recommend checking out this tutorial, which is quite comprehensive:
► Proper throttle-body cleaning guide

If your throttle body is beyond repair, consider replacing the part (costs range between £85 and £215).

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