Throttle Body Cleaning

Keeping your throttle body clean is an essential part of care care maintenance. Why does my throttle body get dirty? Over time the throttle body gets dirty from oil and combustion gas vapors that come from modern PCV (positive crankcase ventilation) systems. Modern PCV systems recirculate back to the intake where gasses are re-combusted. Recirculation is via a hose which is connected somewhere close to the throttle body. During startup, operation and shutdown air intake pressure changes which can push PCV oil and combustion gas vapors back to the throttle body, coating it with deposits. This is normal and no indication of problems. Symptoms of a dirty throttle body include:
  • Poor gas Mileage. Your car's ECU (computer) will attempt to adjust the air fuel mixture to compensate for throttle plates that can't close fully. 
  • Rough idle. Same reasons as above.
  • CEL codes. Your car's ECU may think you have a vacuum leak, faulty sensor, etc resulting in various CEL fault codes
How do I clean my throttle body?
Most modern cars use an electronic throttle body with an electronic motor controlled by the ECU (also known as "drive-by-wire"). NEVER use a screwdriver or pliers to force the plates open with the key on! This can bend or damage the plates, strip the gears in the motor. With the key off and power removed the plates can be manually opened but there is still the issue of preventing the throttle plates snapping shut. Use of sharp or abrasive objects to wedge the plates open can result in damage to the seal of the plates. So for electronic throttle bodies the best way to clean them is with an assistant opening the throttle with the key turned to acc. (power, engine not running). You can also use something to depress the accelerator pedal like bricks, metal bar, etc. Most throttle bodies are easily removed with 4 screws. Because its an electronic connection, its just a connector, no accelerator cable to worry about.

Each car is different, but all require the removal of the air intake to get proper access for cleaning. There will be a few connectors and vacuum lines to remove from the air intake, take note of them. May as well clean the Mass Air flow Sensor and inspect the air filter while the air intake is off. The Mass air flow sensor requires a special electrical cleaner which goes by the name "Mass Air Flow Sensor Cleaner".

Before you close things up its a good idea to lubricate the throttle plate shaft right where it connects to the walls of the throttle body. Use a cotton ear swab to apply some motor oil or white lithium grease from a squeeze tube. 

What do I use to clean my throttle body?
A dry, no oil throttle body cleaner is best because it won't attract oil and gas vapors as fast. Some throttle bodies (like Ford) have a coating that helps seal throttle plates and prevent deposit buildup. Not knowing whether your throttle body contains one of these coatings its best to use a throttle body cleaner rather than the more potent carb and choke cleaners from decades ago. That being said, use of toothbrushes and anything abrasive should be used with caution. Usually a soft rag will do the job.

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