How to clean the throttle body on your vehicle

Image via Wikipedia Gm Throttle Body

Modern electronic fuel-injection systems are some of the most trouble-free systems in your vehicle. However, if your vehicle has accumulated more than 75,000 miles, there is some routine fuel-injection-system maintenance that should be considered. The two most common maintenance jobs are fuel-injector cleaning and throttle-body cleaning. Cleaning fuel injectors is generally not a do-it-yourself project, but you can clean the throttle body on your vehicle with common tools and specialized spray cleaners.
While throttle-body cleaning is good preventative maintenance, it should also help engine drivability. In fact, if you've noticed a rough idle, stumbling initial acceleration or even stalling - all when the engine is fully warmed up - a dirty throttle body could be the culprit. Once you look inside a throttle body, you will probably be surprised at the dirt, gum and varnish that have accumulated there over time.

Setup
Park your vehicle outside in a well-lighted, level area. Because the throttle-body cleaners are volatile, we do not recommend doing this job indoors.
Locate the throttle body under the hood in the engine compartment. Here are some hints on what to look for:
The throttle body is located between the air cleaner and the intake manifold of the engine.
Most throttle bodies are made of aluminum.
The throttle body is connected to the gas pedal of your vehicle with a linkage or flexible cable, which moves the throttle shaft when the gas pedal is depressed. (If you're having difficulty locating the throttle body, ask a helper to press the accelerator - with the engine off - so you can see the movement of the throttle shaft.)
Once you have located your vehicle's throttle body, look at how it is attached to the air-intake tubes. Sometimes throttle bodies are attached with special fasteners called Torx-head screws. If so, you will need Torx bits or Torx screwdrivers to remove these fasteners. More commonly, a flat-blade or Phillips-head screwdriver should do the trick.
There may be one or more electrical wires that connect to the throttle body. Do not disturb these; for purposes of this project, you should not need to disconnect any of these terminals.
While we always recommend that you follow all appropriate safety precautions for these DIY projects, this is even more important for this project. Do not smoke when you are working on your vehicle, wear all recommended skin and eye protection and generally be aware that you are dealing with a flammable spray cleaner
 Tools Required

Screwdrivers, Torx bits or Torx screwdrivers, combination or socket wrenches - this will vary depending upon the fasteners used to connect the throttle body to the intake "plumbing."
Toothbrush or small, soft parts-cleaning brush. Note: Some auto parts stores sell specific throttle-body cleaning brushes. Some throttle bodies have special coatings that can be marred by hard-bristle brushes.
Eye protection.
Flashlight.
Materials
Throttle-body cleaner.
This should be available at your auto parts supply store or auto dealership parts department. Do not use carburetor cleaner.
Household oil.
Cotton swabs.
Paper towels.
Rubber gloves.
The Job:
Park your car outside with plenty of space to work around each side of the engine compartment.
As a safety precaution, disconnect the ground terminal (negative) of your vehicle's battery.
Locate and label any small hoses that attach to the throttle body or to the air ducts that you must remove in order to gain access to the throttle body. You can either use masking tape and mark each hose and coupling, or buy specific labeling tape that helps you remember which hose goes with which nozzle/coupling.
Remove the air duct that attaches to the throttle body. Be very careful to avoid disconnecting any electrical wires or terminals. The air duct to the throttle body is usually held in place with some type of hose clamp which can be loosened with a screwdriver, Torx-head wrench, Allen wrench or other hand tool. Sometimes the air duct is pressed into place, and can be removed with some gentle twist and pull movements. In some cases, both sides of the throttle body are connected to air ducts by means of hose clamps; in this case, you only need to remove one side to expose the throttle body for cleaning.
If you are unable to remove the air ducts to expose the throttle body, stop and do not attempt this project. Let a professional Technician handle the job.

Remove just enough air ducting to expose the throttle body. Be careful not to damage any gaskets that may be present. There are many different types of throttle bodies; some even have two throttle blades (one may work with the traction-control system). Some recent models even use an electronic throttle control, sometimes called "drive by wire." With all of these differences, though, you will still likely expose a throttle body very similar in appearance to the one shown here.
If you have not already done so, put on rubber gloves and eye protection. Once the throttle body is exposed, spray the throttle-body cleaner inside the air duct, and use the brushes to gently dislodge the dirt, gum and varnish that are present. Note: Be very careful not to let the thin, plastic spray nozzle (or anything else!) fall into the throttle-body opening. Periodically wipe the residue clean with the paper towels.
Repeat this process until all the interior surfaces are clean to bare metal. Use the flashlight to get a good look at your progress.
Before replacing the throttle-body ducts, put a drop of household general-purpose oil on the shafts of the throttle shaft where it enters the throttle body. Use a small cotton swab, and don't overdo it - just a small drop of oil will help keep the throttle blade rotating smoothly. One drop should be fine.
Use more paper towels to clean up any residue and liquid that may have spilled onto the engine or surrounding components.

Reinstall the throttle-body ducts, tightening the hose clamps to the same level of tightness as before. In other words, consider how much force you used to loosen the fastener, and try to tighten the same amount.
Once you have reattached everything, and removed any tools or materials from under the hood, reattach the battery and start the engine. You may notice an initial stumble or even an initial rough idle as the cleaner fluid and residue that may have entered the intake manifold is burned off. In the worst cases, you may even notice a whiff of white exhaust smoke. In addition, many times the engine control computer must "relearn" some parameters after a battery is disconnected. This is normal.
Let the engine idle for a minute or two. Then take your vehicle for a test drive. Depending upon the amount of dirt, gum and varnish that was in your vehicle's throttle body, you may or may not notice a difference in drivability and performance, but remember - this is a preventative maintenance effort to improve the long-term reliability of your vehicle. The throttle body should be cleaned every 75k miles.