I just finished troubleshooting some rough idle and think a dirty throttle plate was one of the symptoms (a dirty PCV valve was also likely a contributor). FYI this is for a first gen TL (1996 3.2 TL).

Surprisingly getting into the air intake system is rather straightforward ...

* First, make sure your engine is cool as you will need to access the engine compartment and temporily disconnect some coolant tubes. Assemble your tools. You will need a socket wrench with 10mm and 12 mm sockets, 12'' or bigger socket extender, phillips screwdriver, needlenose plyers, throttle body / carb cleaner, and throttle body gasket (optional).

* Remove the plastic engine cover by removing the four 10 mm nuts
* Remove the black throttle cable / IACV cover by removing the two 10mm bolts
* Unclip the air box clips (should be 4)
* Disconnect the vacuum hoses connected to the air box tube between the air box and TCS. Loosen the ring clamp between air box arm and TCS module.
* Remove the air box tube including air filter. Check your air filter as a dirty / blocked filter could be a contributing factor to sluggish performance or idle issues.
* Disconnect the electrical plugs and vacuum hoses connected to the TCS module. The plug on the bottom is the most difficult, the rest should be quite easy.
* Unbolt the arm holding the TCS in place attached to the chassis and the TCS module. This guy takes a 12 mm socket and you'll likely want to use the extender to get to the bolt attached to the chassis. Remove the arm.
* Remove the ~8 inch black stabalizer arm which connects the TCS module to the throttle body by removing the two 10mm bolts
* Loosen the ring clamp on the TCS and remove the whole module
* Clean out any grime in the TCS (there was none in mine)

* You can now get a glimpse of the throttle plate (shiny gold 3''/4'' disk inside of the throttle body). You can rotate this disk by applying the throttle via the throttle / cruise control cables.
* Remove the two 12mm (I think) bolts, two 12mm nuts, and necessary vacuum hoses to disconnect the throttle body.
* Use throttle body cleaner to clean out all the grime on the throttle body and especially around the throttle place (move it with the throttle cables). You should also clean around the idle adjusting screw and openings for hoses into the back side of the IACV. Shine those pieces up.
* Optional - remove and replace the throttle body gasket (it's cheap, just have to have it in hand before starting the job).

* Reassemble and test
* It helped me to reset the ECU (by removing the battery terminal for 20 seconds) so the idle learning process was repeated

 

Great DIY. Thanks a lot maybe I will take this on soon.