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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.
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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.
Here you can
see the initial DIA of the base of the TB is about 2.2".
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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.
You can see
how the DIA of the bore has now been increased to approximately
2.35".
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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.
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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.
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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.
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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:
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