Monday, April 8, 2013

Cleaning a Jaguar Throttle Body

If your car runs rough when idling, the cause just might be a dirty throttle body. The throttle body controls the amount of air the engine takes in, and when it gets dirty, the engine can't idle smoothly. Over time as your throttle body collects carbon the air volume which passes through it changes very slightly.  Once you look inside a throttle body, you will probably be surprised at the dirt, gum and varnish that has accumulated over time. All connecting tubes and duct work should be checked for damaged, tears dirt or clogs also. Some of these may be cleaned with detergent and water (dry well) and a long brush.

Throttle Body Cleaner and MAP Cleaner
Here's how the throttle body gets dirty. When an engine shuts down, hot exhaust gases and unburned fuel float to the top of the engine. As the vapors bake from the engine heat, they form black sooty carbon deposits inside the throttle body. In addition, the shaft for the butterfly does not get regular lubrication by the owner, this results in wear and a hard/rough pedal.

Old can style
First, use special cleaner.  Sea Foam Deep Creep is my first recommendation. Throttle Body Cleaner, my second, do not use regular carburetor cleaner.  Do not let any liquid contact painted surfaces as this will deface them. 

There are five (5) ways you can service this throttle body for your car.

  • Clean the unit off car and replace
  • Clean the unit on car, engine off (OCEO)
  • Clean the unit on car, engine running (OCER)
  • Swap dirty unit for a precleaned backup unit
  • Swap dirty unit for a new unit.
The safest way to clean the throttle body short of a swap out is off car.  This will allow access easily to both sides of the
Clean Throttle Body
butterfly plate, less likely hood of other damage and an overall better job. The OCEO procedure should be done with an abundance of clean lint free shop towels (like a detailers cloth). Red shop towels should not be used. The generally preferred method is to spray the solution on to the towel and using light pressure, clean the throat and the plate. Do not allow cleaner to saturate the TPS device, this could damage the sensor. The OCER procedure is done more by spray the cleaner, letting it do the work, rather than wiping. This procedure can be preformed by two techniques. Described below, we will call the first general cleaning and the second intermediate cleaning.

  • General cleaning: Remove duct work to expose the intake side of the throttle body, set parts aside. Start engine, which will run roughly. Using your cleaner of choice, spray 1 or 2 second blasts into the unit, washing the throat and the butterfly plate. Continue till clean.  Heavy deposits may require manual cleaning. An additional person is helpful to work the gas pedal as the engine will stumble as the cleaner is sprayed.
  • Intermediate cleaning: This is done to maintain a previously clean unit. This is done as described as above or by the addition of a "spray cleaning" hole previously drilled into the duct work.  You drill an 1/8" hole into the plastic duct work near the throttle body.  This will be sealed by a sheet metal screw afterwards, which will then serve as your service port thereon. Remove the duct before drilling to catch any drill scraps. TO USE: remove the screw, with the engine running, spray blasts of cleaner into the hole using the straw that comes with the can (don't drop the straw, hold it with your fingers to be safe). Do this every 3 months to maintain the clean unit.  There is no chance of puddling using this method and because it is concentrated, the small amount of carbon is easily removed. Every 9 months visually inspect the throttle body for additional cleaning.
The last method is simply to preclean a unit and have it standing by.  This affords both speed and safety. By buying a spare unit (new or used) you can prep it at your leisure and with greater care. This allows for checking for wear on the shaft and oiling the shaft, and a more complete cleaning.

It is a good time to also clean your map sensor using the proper cleaner.


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