View Full Version : How To: Throttle Body Rebuild / Disassembly / Assembly

02-15-2010, 10:38 AM
I couldn't find a write-up on how to disassemble and reassemble a KA throttle body when I started tearing mine apart to clean it up, so I thought I'd write one for anyone else out there who wants to clean theirs up. I just couldn't stand the thought of putting a dirty throttle body back on my cleaned up intake manifold.

I neglected to take many pics of the dis-assembly since I was more interested in keeping track of everything. I will write this as a guide to assembling a throttle body but just reverse the steps to take it apart.

screwdrivers - flat and phillips
14mm wrench
small metric allen wrench - not sure what size
needle nose pliers
WD-40/Liquid Wrench

*Optional stuff*
6mm x 1.0 tap
6mm x 1.0 bolt (bolt from spark plug wire holder)
vice grips

Start with one dirty KA throttle body housing.

When you disassemble, keep the parts in order.

After it's disassembled, clean it up. In my case, I media blasted it and then clear coated it (powder coat).

Start by reinstalling the rubber seals on each side of the throttle body (TB). To remove these, use a pair of needle nose pliers and a small screwdriver. Lightly pinch the lip of the seal and pull it out of its groove. Just be gentle since its old rubber and especially if its cold since it will be brittle. To install, just gently work them into place.
Seal in place.

Reinstall the main shaft. I lightly greased the areas that were going to make contact with the rubber seals and housing. It will be snug going in (and coming out). To take it out, tap on the TPS end of the shaft with a hammer. To reinstall, make sure it is lined up and lightly tap it into place from the throttle cable side. It doesn't take a huge whack.

Make sure it is oriented in this manner so the extension part on the shaft makes contact with the housing as it rotates from closed to open (it will hit the set screws when they are installed).

Now, reinstall the throttle plate. This will help you line up the shaft in the housing as the throttle plate will not fit if the shaft it not centered. There is a slot in the shaft that the plate slides through. Orient the shaft as it is in the picture, then slide the plate through and line up the screw holes in the plate with those on the shaft. When removing these screws, be careful no to strip these screw heads. This is where I used the liquid wrench and patience. They are in there TIGHT. Work them out slowly but if you strip the heads, it is pretty much game over. I put a little lock-tite on the thread for reassembly.

Next, its the throttle cable side. These springs are what had me initially intimidated since I thought they would fly apart. Not the case. They really don't have much tension on them and are not "spooled" on there. The just sit in place and hook on where they are supposed to. There are a lot of little bits and pieces to this side, but there is only one way it will all go together. So, make sure you have the correct orientation as below.
Assembled in my hand
Half installed on the main shaft. Note that everything slides over that central black bushing.
The other half

Put on the cable wheel (I powder coated it black while it was off). Note it fits as a "dome" over the first set of springs. It is a snug fit to slide it on. It can only go on in two orientations - correct and 180* off. It's hard to mess up. Hook the springs on to the small shaft parallel to the main one (round end of spring) and hook the other side on the cable wheel and main shaft at the base (the square end of the spring). I'll post a complete shot at the end for reference. The bushing for the cruise control pulley is sitting on top of it for the next step.

Slip on the plastic spacer over the bushing. Remember this is old plastic. Fragile stuff.
Then, slip on the cruise control pulley over that...
then the bottom half of the spring keeper...
and finally, the spring and top side plastic keeper.

Before you put on the washer and nut, make sure you have all your springs hooked on and orientated as shown below.

If it's good, then slide on this rubber buffer/stopper...
and then the teeny tiny C-clip. You can use a flat screw driver to pop this off by pushing the open end with the flat surface of the screw driver. Just make sure you don't launch the clip.

Finally, put on the lock washer and tighten down the 14mm nut. The nut will tighten down against the main shaft which will hit it stopper set screw at the WOT position, so you don't have to figure out what to hold it with. The washer below the lock washer is oriented incorrectly in the pictures above. It is correct as shown below. Above, it will not let the TB open.

Install the set screws, one for idle and one for WOT. Try to remember what they were like before you took them apart. And now, you are done with the hard half.

On the other side, slip the TPS back into position and tighten the two screws. This will only fit on in one direction since it is a D-shaped end of the main shaft.

I also took the opportunity to plug another vacuum hole while the TB was off. On the under side of the TB, there is a small port that runs a vacuum line to the mess of emissions stuff at the back of the manifold. All my emissions stuff is gone and this port is no longer needed. I used a pair of vice grips to pull the metal port out of the TB housing. It came out pretty easy but just rotate it back and forth while pulling it out. I then tapped the hole with a 6mm x 1.0 tap. Like so...
I used one of the bolts that mount the spark plug wire holders to the valve cover which just happens to be the right thread pitch and the perfect length. I put some RTV on the bolt threads and tightened it into place.

And the finished product, ready to go back on the manifold.

I am sure the process is the same for any other TB with this design - Q45, SR, RB, 300ZX. I hope this gives someone else out there the confidence to tackle what seemed to be a daunting task.

02-15-2010, 10:43 AM
im sure this will help alot of people..nice write up

02-15-2010, 03:18 PM
Great job man.. Thanks for sharing a write-up too. +1

02-15-2010, 03:48 PM
very nice.