Rick's Free Auto Repair Advice

Air Induction Service

What is Air Induction Service

Air induction service is a cleaning procedure to remove carbon buildup from your engine’s throttle body and intake valves. The service can solve some performance related issues if they’re caused by carbon buildup. Most engines develop some carbon buildup on the bore of the throttle body. As the buildup accumulates, it can affect idle quality. Carbon buildup on the intake valves is a more serious problem most commonly found on engine with gasoline direct injection (DI). DI differs quite a bit from port injection and is far more prone to carbon buildup problems. Read on for more information on when and how to clean off this carbon buildup

How does your throttle body get carbon buildup?

Most late model fuel injected vehicles have an electronically controlled throttle body. The throttle plate is opened and closed by a small electric motor driven by the vehicle’s PCM/ECM based on input from an electronic accelerator pedal position sensor. When the engine is off, the throttle plate is closed. At startup and idle, the throttle plate motor opens the throttle plate slightly to allow enough air into the engine to maintain idle and keep emissions low.

When you shut off the vehicle, hot fuel

air induction service

Carbon buildup in an electronic throttle body

vapors rise to the top of the vehicle and sometimes accumulate in the throat of the throttle body. As the residue cools, it forms a hard black carbon deposit. If the carbon buildup reaches a certain level, it can affect idle quality, resulting in a rough idle and even a no-start condition. During an air induction service, the technician cleans away the carbon buildup and performs a throttle body “relearn” procedure to re-establish a new “base level” fully clean position.

electronic throttle body

Cleaned electronic throttle body

In addition to cleaning the throttle body, technicians also clean the Manifold Airflow Sensor (MAF) by spraying the

sensing elements with MAF sensor cleaner.

Intake valve cleaning for DI engines

Those same hot vapors can also cause carbon buildup on the back of

gasoline direct injection

In a GDI system, the fuel sprays directly into the cylinder

intake valves. Over time, that buildup can cause performance problems in the engine. Carbon buildup on the intake valves is far more common on engines with DI because that type of fuel injection system injects fuel directly into the combustion cylinder, as opposed to spraying fuel through the valve opening in a port injected engine.

All fuel contains fuel injector cleaner and it’s that cleaner that reduces carbon buildup in a port injected engine. But that cleaner never touches the valves in a DI engine, so air induction service on those engines is a good idea

How intake valve cleaning is done

The technician removes a vacuum line from your engine and attaches a dispensing device that meters the flow of a special cleaner into the engine intake. The technician starts the engine and opens the flow of the cleaner while increasing idle speed. The cleaner comes into direct contact with the intake valves and begins to dissolve the buildup. After injection, the technician lets the car sit for a few hours to allow the cleaner to do its job. Then they take the vehicle for a test drive to blow out any remaining carbon buildup. This service typically runs between $150 and $225, depending on the shop’s labor rate

If the carbon buildup is too severe to be removed by this method, they have to remove the cylinder head and blast off the carbon using ground up walnut shells.

Can you perform your own induction cleaning?

Yes. I’ve posted articles on MAF sensor cleaning, throttle body cleaning and intake valve cleaning. Find them here:

How to clean an electronic throttle, see this post

How to clean a MAF sensor, see this post

How to clean intake valves, see this post

How often do you need air induction service?

Car makers have published multiple service bulletins warning dealers not to perform routine air induction cleaning services, and to perform air induction service ONLY to correct a carbon buildup performance issue related issue. In those cases, an Air induction cleaning service CAN remove carbon buildup and restore performance. But it is NOT recommended as a routine preventative service.

That advice has unfortunately been proved wrong as car makers have gained more experience with DI engine designs. Now, air induction service IS recommended as a preventative measure approximately every 30,000 miles. However, some engines need it more often.

Symptoms of carbon buildup

• Rough idle or hard starting caused by carbon buildup in the electronic throttle body. Make sure the shop confirms that the carbon buildup is the cause of the rough idle before agreeing to the induction cleaning service.

• Hesitation on acceleration caused by debris accumulation on the MAF sensor elements.

• Rough idle and lack of power caused by carbon buildup on the back of valves in DI engines.

Air Induction Service Fuel induction service cost

A complete air induction service takes about an hour, so shops usually charge around $150 to $225 for the service. The technician must remove the throttle body and clean it by hand. It should never be cleaned while in the vehicle and can’t be cleaned simply by spraying throttle body cleaner into the throat. The fluid can seep into the electronics and destroy them. The top engine cleaning and MAF sensor cleaning are done at the same time.

©, 2018 Rick Muscoplat

Posted on by Rick Muscoplat

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