Installation date: 1/5/02
There are about 3-4 off-road companies currently offering bored-out throttle bodies; I chose to go with Jeepers And Creepers because of their price and my past good experiences with their products and customer service. The initial cost is $225 but you get $125 back after you return your old throttle body. Yes, J&C uses “used” throttle bodies, but they are carefully cleaned and machined, so that the throttle body you get in the mail is probably in better shape than when it you drove your rig off the lot. I’ve tried a lot of engine performance mods, from cat-backs to ignition systems, and this has been the best mod I’ve done in terms of bang for the buck, in fact, I liked it so much I got another TB to install on BigRed (our ’95 XJ). Throttle response improved and the Jeep seemed to “pull” a lot more in the mid rpm range, which is exactly what J&C claimed the throttle-body would do.
Our initial testing of the bored out TB was on our ’01 XJ Limited to watch for any changes in mileage, since we don’t really keep track of that on our TJ, the photos are from the install in our TJ however. Unfortunately we didn’t see any change in mileage. The installation is just the same regardless of what model Jeep you have.
The throttle bodies are available for both the ODBII and non-ODBII versions of the HO 4.0L, you just need to specify whether you need a TB for a ’91-’95 4.0L or a ’96+ 4.0L (’96 marked the beginning of the ODBII emissions system). The TB’s come with all the sensors already on them, so installation is a snap. There’s no difference btwn XJ, TJ, and ZJ/WJ throttle bodies.
What J&C does is to have the lower “neck” of the TB bored out below the throttle plate, so that the bore of the TB is constant throughout its height. No changes to the throttle plate are required.Here you can see the initial DIA of the base of the TB is about 2.2″ and you can see how the DIA of the bore has now been increased to approximately 2.35″.
The first thing to do is remove the intake tube from the throttle body. Next, there are three sensors to unplug and 3 cables to unhook, marked in this photo by the yellow arrows.
If you’ve got a non-ODBII 4.0L (ie: ’91-’95) there are only 2 sensors on the TB to unplug.
Next, using a 10mm deep socket, remove the 4 bolts attaching the throttle body to the intake manifold. The gasket may or may not come off with the throttle body — in our case it stayed on the manifold. This gets reused with the new TB, or J&C can include a gasket with the TB in case you need a new one.
Put the new TB on the manifold and replace the four 10mm bolts. Be careful tightening these down, since the bolts go into the cast aluminum manifold they just need to be good and snug, not super tight or you could damage the manifold.
Then reattach the plugs to the sensors and the throttle cables to the throttle arm. Finish it up by replacing the intake tube on the TB and you’re ready to go.
J&C also instructs you to disconnect the battery for a few minutes to reset the engine’s computer once the new TB is in place. This is so that the computer can adjust to the new TB.
As mentioned earlier, the initial testing was on our daily driver ’01 XJ which has a stock exhaust and a high-flow intake as the only other mod. The “power” gains were noticeable almost immediately, though I have no dyno numbers to back up my claims. It did make more of an improvement than any other engine mod we’ve tried however, and I’d recommend installing a bored-out throttle body as the very first engine mod you do, regardless of if you get it from J&C or someplace else.
For more information, contact:
Jeepers and Creepers
San Francisco, Ca.