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Alternate 60mm Jeep Throttle Body Mod

The original write up is here, some things I did are different:

Im modding a Jeep 60mm TB from the mid 90's 4.0L Cherokees to fit on my Mitsuneon! Some of them actually neck down to 55mm at the bottom, but that is easily remedied (which I did not do yet, waiting to sandblast my IM that im porting out). 55mm is still a HUGE improvement over a 49mm TB that comes stock. From what I have read, although no real confirmation, a Jeep ATX TB will be 60mm the whole way through, while the MTX TB is 55mm at the bottom. 6mm may not seem like much, but remember that the area of a circle is exponential. Going from a 49mm to 52mm TB on my DOHC Neon was a great mod, so I have high expectations for this one!

The only parts from the Jeep TB I used are: body, butterfly plate, IAC tip.
Parts from the Eclipse TB is: Sensors, throttle shaft.
The spring is actually coming from an old Neon, because it fits better than the Eclipse or Jeep IMO. But all three work great!
Other material: Half inch button plug, RTV, two M8x25 1.25 pitch allen head bolts, two M8 lock washers, gasket material. Also, I replaced all the screws on the TB with allen headed bolts. Dremel with reinforced cut off wheels, sanding drums, carbid bit. M5x.8ptch tap.

Here is a picture what a stock Jeep TB looks like:

Here is the bottom of the Jeep TB after it is disassembled. First thing is to disassemble both throttle bodies and keep the parts seperate!:

Now through these next steps I would read them first and then cut all of the material off at once.
All of the red on here you are going to cut off. Dont forget to smooth the edges out using the sanding drums on the Dremel!:

Also, widen the spring slot back, otherwise the spring slot will be WAY too small:

Now use a small carbide bit (and PLENTY of WD40) and widen the two holes circled in blue. Widen them towards the throat of the TB (these are already widened in the pic). Just widen them until you can bolt it up easily to the IM. Remember you NEED to use allen bolts here (M8x1.25ptchx25mm)!:

Now tap a hole that is M5x.8ptch where the red dot is. You should not have the threaded hole where the red X is now. While you are using the drill bit to start tapping the hole, run it through the old vacuum port to clean it out.

Now take the IAC passage and cut the nub off.

Now, remember when you cut the vacuum port off and you drill it out with the bit for the tap? You can do one of two things here. Either JB Weld it shut, like I did, or tap it and put a bolt into it. The area that has a rectangle around it is also where you need to remove some material to make clearance for the bolt. There is a better pic of the clearance too.

Here is my modded TB body (left) with a stock 420A TB on the right:

Here is a close up of my TB body (the red area is what I still needed to cut off to allow clearance for the throttle shaft). Also, if you notice the empty bolt hole to the right in the red area, that is the old shaft stop screw for the Cherokee, it needs to be moved to the other side for the Eclipse shaft. Took five minutes. You want to set the bolt to a height that allows the TB to shut and open smoothly, so you can feel/see that the plate fits into place fine. I used a M5x.8 bolt with nut for the stop. Move the bolt to desired level, then lock down with the nut:

Here is the Eclipse IAC with a Jeep tip on it, this allows it to seat correctly inside of the idle air passage on the TB:

And here is the Eclipse throttle shaft, notice I had to cut material from the spring perch for the butterfly plate holes to center in the TB. I still need to widen the shaft slot to fit the 60mm plate in:

K, here is the finished Eclipse throttle shaft. I cut some material away from the spring perch on the edge to hold the spring better (see red arrow). Also, the shaft slot has been widened to 60mm using a Dremel, and a small bastard file.

Here is the gasket I made using gasket material, and a plug I bought from ACE to fit the existing idle air passage on the Eclipse IM. It is a half inch button plug (I think thats what they call them). It has metal tabs on the back that hold it in place. I took a hammer and tapped the plug while it was on the IM to flatten it out on the IM. Ill put some RTV around it when it goes on the IM. Some people plug that hole with a rubber plug, but I dont want the chance of it coming off and entering the motor. The button plug has a 1/16 edge all the way around the hole. More secure IMO.

And finally, here she is!

NOTE: For the spring I ended up cutting one coil off the Neon spring and bending a tab to fit underneath. It was much neater this way and the tension feels the same.

When I move the throttle shaft it opens all the way, and feels really smooth. No snags opening or closing on the plate.

Alright, and here is the plug in the old IAC passage with some silicone for good measure. I know its dirty in there, but thats 248000 miles of build up! As soon as I find a sandblaster around here I will have my other IM sandblasted and ill finish opening up the neck to 60mm:

After you bolt the TB up using the M8x25 1.25 pitch allen headed bolts, you have some adjusting to do. There are two 10mm bolts on the front of the IM with the throttle cable attached. Loosen them and move the cable back or forth until the throttle shaft is resting where you set it earlier with the shaft stop bolt and the cable has no slack. Not overly tight or loose, just take the slack out.

And here is the TB on the car!

First time I fired it up it idled at 4000 :shock:
When I put the IAC in I set it to the same height as the Eclipse IAC. So I pulled out the IAC and adjusted it a little more (see below for my final method of adjustment). This time she idled, but I had a whistle that was random and it would hang at around 2k for a few seconds then return to idle. I drove it up to Advance to have the codes read (I always have the CEL on for the EGR) to make sure that the IAC or TPS was not messing up, they were fine.

So I brought it back home and pulled it apart. I took the vacuum line that ran from the evap canister to the TB off, and put it to an empty port on the intake manifold. Then I plugged the nipple on the TB. I also realized that the butterfly plate was upside down from when I first bought the Jeep TB (part number was normally on top) and I flipped it around. The butterfly plate made the biggest difference, I could tell that it seated better in the body.

Now it idles at 950+/- which is where its normally at, it does not hunt for idle every two seconds, goes right back to idle when coming to a stop, and best of all NO WHISTLE!

Overall great improvement. Smooth throttle response and a definite increase in power!

This should take a few hours, but is worth it as this project cost me about 60 bucks total including Jeep TB from eBay, used Eclipse donor TB, and materials!
Make sure that when you are shopping for a Jeep TB you grab one with the Jeep IAC sensor, that way you have the Jeep IAC tip (which btw is a major PITA to get).

How I Set My IAC:

1) I pulled the tip out from the sensor.
2) When I put the sensor back into the TB, I had to push it towards the TB to have the sensor seat properly. You should feel resistance. What you want here is for the tip to be out far enough to now allow you to seat the sensor properly. Just push it in then bolt it up.
3) Thats how I did it, you may need to adjust it more or less depending on your car. This is a great starting point though.

Document statistics: Last modified on 2008-07-02 07:09:46 by teklein

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