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            DR’s (somewhat) simple throttle shaft/cam install.



The below is not fully vetted as it has only been done on one set of throttle bodies so far so use the below for what it is  (as of now just a suggestion on how it could be done)

Caution: work on one side throttle body at a time so you do not cross mix any parts. 

    First--  completely clean the throttle bores and the throttle plates so accurate, pre-disassembly measurements can be taken   (be real careful here to not get any cleaning solvent into the stepper connector pin area or into the TPS pin area)—


Or, just remove the steppers, then  mark and remove the TPS from the throttle body. Caution: if you remove the TPS before cleaning then make darn sure that the TPS to throttle body positioning is accurately and well marked so the markings  aren’t washed off during the cleaning procedure.


When I did mine I left both the stepper and TPS on the throttle body  but covered the pin areas and  was very  careful to not saturate the steppers or the TPS with cleaning solvent.


   Next--  take clear pictures of the throttle plate position in the throttle bore (so you can positively get it re-installed in the exact same position that it was in the original).

I also put a paint mark  “T” for ‘top' on the top of the throttle plate to make improper reassembly unlikely.



 Be sure to take pre-disassembly pictures of the base idle screw clocking position. Also, take pictures of the return spring positions, spring directions, and how they are attached.

   Next-- carefully, with precision and care,  mark the TPS position to the L/H  throttle body housing. (this is a very important step as you need to accurately re-install the TPS back to the ‘very same' position on the throttle body).

Use something like  thick  marking paint on both the TPS and the throttled body so you have something to scribe accurately, then scribe the TPS to throttle body on both sides (top and bottom)  of the TPS. (be accurate as possible with this step)





 If working on the R/H throttle body  carefully pry the outer throttle ‘shaft cover cap' off. Use a flat screwdriver over a wood or plastic fulcrum, or better yet use very small achilles heel to evenly work it off.  (the cap can be somewhat difficult to remove without damage)




Both the TPS on (L/H) side TB and the ‘shaft cover cap’ on the  (R/H) side TB  must be removed to access the retaining circlips that are under them (the shafts are held in place by external circlips under the TPS, or under that ‘cover cap’). 

A small right-angle snap ring pliers work good here. Do not try to use a screwdriver to pry the circlip apart as it is not a tight fit so a distorted circlip could cause problems later.





                            ---Pre-disassembly measurement ---
   To start--- place a  .0015” thick  (that is 1-1/2 thousandths) feeler stock between the top of  throttle plate and the throttle bore, then place a .0015” thick feeler stock  between the bottom of the throttle plate and the throttle bore   (important: make sure that the feeler stock is perfectly centered and straight). You should now have  a .0015” feeler stock at both the very  top and at the very bottom of the closed throttle plate.     (the throttle plate is sort of elliptical with the high points at the very top and very bottom)


Now see if the  .0015" feeler stock (top and bottom) allows the shaft stop lever to j-u-s-t contact  the idle stop screw with no gap. If no gap then see ‘next’, if there is a gap then skip ‘next’.


   ‘Next’-- if no gap per the above then try a .002" thick feeler stock top and bottom of the throttle valve. Hopefully the .002” thick feeler stock prevents the  TB idle stop lever from fully contacting the idle stop screw.  (you ‘must' have a slight gap between the lever and base idle screw to proceed).


You can try .0025” thick if you need to, or even .003” thick, but anything over .002” might not fully conform to the round curvature of the throttle plate to the throttle bore and prevent an accurate throttle plate to throttle bore repeatable (precise) gap. If you need to go over .002” thick then I highly recommend using softer brass shim stock as the feeler stock material (cut brass to standard feeler stock width) as  brass shim stock should conform to the throttle bore curvature even at .003” thick. 


Note: for the  above,  use the thinnest feeler stock that will hold the stop arm 'just slightly' off of the base idle screw at closed throttle. But, (important) be sure to use the very same thickness feeler stock on each side throttle body.   




   Next-- once you have the throttle plate to throttle bore  position held precisely at a fixed thickness, then, use different thickness feeler gauges to ‘accurately’  measure the throttle shaft stop lever to the base idle screw tip gap (write the thickness number down as you will need that exact measurement at re-assembly).



On the set of throttle bodies that I have done it looks like Bing set the original factory throttle plate air gap to around .0015” (maybe slightly more but not much)  but not nearly as much as .002". This is the air gap around the perimeter of the closed throttle plate to throttle bore. 
If you hold the throttle body up to a bright light with the throttle plate fully closed on the base idle screw stop you should be able to see that base air gap as an even ring of light showing around the perimeter of the throttle plate. (note this ring of light as it should look the same on the post-repair throttle body as it does on the pre-repair throttle body. Note: you might have to slide the throttle shaft in or out slightly to get an even looking light ring around the throttle plate.


   Next-- use metal working bluing fluid (best way), or you could use a  blue ‘Sharpie Pen’ to mark along the  sides of the throttle shaft on the throttle plate, then when dry, scribe-mark precisely along the edge of the throttle shaft. (this is needed for getting a very accurate throttle plate re-clocking position at the throttle plate re-install). Do not skip this step as it is very important for accurate re-assembly.




   Next--unhook both return springs (a loop of fishing line works great for disconnecting and re-connecting the return spring under the lever).




   Next--  remove the shaft retention circlip and plastic washer, then remove the throttle plate and throttle shaft from the  throttle body. (caution: do not lose the plastic outer hat-shaped collar that is under the shaft lever).  Caution: do not try to pry the circlip out with a screwdriver as any circlip damage or distortion could prevent it from staying on the shaft in long term use.




   Next-- you might want add a little more grease to the throttle shaft needle bearings (at least I did on mine).


    Next--place the hat-shaped shaped nylon (spring-centering) collar under the stop lever. Then install the shaft, then re-install the nylon washer and circlip  on the shaft. (don’t hook up the return springs yet)


   Next-- re-install the  throttle plate in the  shaft cutout  making sure that it is installed in the correct clocking making sure to match the throttle plate scribe marks up to match the throttle shaft sides (verify that it is installed correctly from  your original pictures).
This re-sets throttle plate ‘clocking' back to  where it was originally.


Now, reinstall both  return springs. (fishing line works great for inner spring). Once the springs are hook up then verify that the inner spring lower curved tail is firmly  snapped around the bracket plastic and that it hasn’t slipped in to rest on the body casting.




Then, verify that the shaft is somewhat centered latterly (look at the raised square on the throttle shaft on each side of the throttle bore).




Then, very lightly tighten the throttle plate screws (very lightly),  just enough to hold the throttle plate from moving.


Again, re-verify that the scribe marks are perfectly  aligned along the throttle shaft.


After all the above is verified then  reinsert the .002" feeler stock (or whatever your original feeler stock thickness was)  between the top and bottom of the throttle plate to throttle bore (straight and centered). Then  allow the factory springs to close the throttle plate against the feeler stock (maybe help it just slightly with your fingers to be sure that it conforms the feeler stock to the throttle bore curvature). 


   Next-- back the throttle plate screws out slightly (to allow throttle plate to self center in the throttle bore against the top and bottom .002” feeler stock  (or whatever your original feeler stock thickness was).

Then,  re-check that the throttle plate scribe lines are still aligned with the throttle shaft edges (this is very important). Then fully tighten the throttle plate  screws. Then re-check that the scribe lines still line up EXACTLY.


   Next--  remove the .002”feeler stock (or whatever your original feeler stock thickness was) then verify that you still have a little needed lateral movement in the throttle shaft with throttle plate opened a little (very little lateral movement needed but some is needed to prevent the throttle plate from wearing the throttle bore in use).

Also, re-verify that the square edges on throttle shaft align somewhat with the insides of the throttle bore. It doesn't have to be perfect just make sure that one side square edge isn’t sticking way out into the throttle bore.


   Next-- open and close the throttle plate by using the cable cam to open/close it a few times, you might  even allow it to snap closed a couple of times.


   Next--  reinstall the .002” feeler stock  (or whatever your original feeler stock thickness was)  between the top and bottom of the throttle plate and throttle bore then allow the throttle plate to close tightly on the .002” feeler stock (or whatever your original feeler stock thickness was).

   Next-- re-measure the gap between the base idle screw and the stop lever to see how close it comes to the pre-replacement measurement.




If measuerment is within a thousandth or so you can just leave it. If it is not close then you will need to adjust the base idle screw in or out  until you get the same gap as you measured on the original shaft/cam.  (that number that you wrote down).
    --See below for more info on this!--


(with the feeler stock between throttle plate and throttle bore)-- if the original (pre-repair) measured gap between the stop lever and the base idle stop screw was the same (or very close)  between both throttle bodies,  then you have an easy decision as you just re-set both sides the very same  pre-repair measured  gap.


The big decision will be (IF) you want to use the individual (pre-repair) stop lever to base idle screw gap measurement on each side if the measurement  was significantly  different side to side as originally measured  (they shouldn’t have been).

Or to use the very same gap on each side to keep them even.


Until we see many more samples we are not going to know if there is a lot of variance in the pre-repair measurements between sides or if most will be like mine where both sides (pre-repair measurements)  measured out to almost identical. 


My suggestion at this time is to do the pre-lever/cam install ‘stop lever’ to ‘base idle screw’ measurements on both  throttle bodies  before doing any work. If they measure out close to the same then go ahead with the shaft/cam installation.

If for some reason the sides don’t pre-measure out to be close then you need to stop right there then to try to understand why they are not close.            



                    --Tools needed--



**You will need a proper low profile clamp removal pliers to remove the throttle bodies from the engine ( I used low profile axle boot ring pliers)



**You will need something to remove the shaft circlips (like small snap ring pliers) right angle makes it easier to see and work but straight should also work.



**You will need a good (proper) fitting screwdriver to remove the throttle plate screws without damage. 


**Some marking fluid (or a sharpie) to mark the throttle plate.


**A sharp fine point scribe to precisely mark the throttle plate along the throttle shaft.


**You will  need some standard feeler gage stock in .0015”, .002” .0025”. If you need thicker stock then it should be brass.




**You will need  a set of standard feeler gauges (to precisely
   measure the stop arm to base idle screw gap)


**A loop of fishing line to unhook/re-hook the bottom return spring.


**You will need a way to pry the shaft cover off of the R/H throttle body (a screwdriver over a fulcrum  m-i-g-h-t work (I didn’t get it to work but I didn’t try very hard either). I had much better luck using a small achilles heel to work the cap off.




                    __Pitfalls to look out for__



When removing the throttle bodies be careful of the throttle cables once removed so you don’t push the inner cable back into the outer sheath (if pushed back they can come unhooked inside the splitter box).


When reinstalling the throttle bodies make sure that the throttle cables fully seats all the way around the cam groove. (double check this).


If removed be sure to put the black plastic throttle cam covers back on the cables before hooking  the throttle cables up to the throttle bodies.


Make sure that the re-installed throttle cables properly seat in the throttle body bracket (locked in by the clip)- give them a little tug to be sure.  


Before starting the engine do a new TPS re-learn as the new shaft as well as removing/reinstalling the TPS could have changed the TPS  voltage output slightly. 






  • Like 3
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Good explanation and instructions with clear photographs!  :thumbsup:

Sure hope I don't have to do it on the 09 RT... 

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  • 2 years later...
On 5/7/2019 at 1:15 PM, dirtrider said:


            DR’s (somewhat) simple throttle shaft/cam install.





Got my new BING shaft this morning. I printed your post, followed it closely, and had the job done in about an hour. Fired it up and everything seems to be working great.


Thanks for your effort in putting this together. I'd have been lost otherwise.



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  • 1 month later...

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