The Rubicon Express 62mm throttle body is shown installed on our 4.0L I-6 engine along with a K&N FIPK Gen II air-intake system. With the new throttle body in place, we're afforded quicker accelerations and greater power throughout the rpm range.
There are lots of methods to creating more power in 4.0L Jeep engines. Some are easy bolt-on upgrades, while others require extensive modifications and engine disassembly for installation. With so many rusted nuts and bolts on the high-mileage 4.0L in our '97 Cherokee, we elected to go the easy route and steered clear of tackling major disassembly for fear of breaking a stud off in the head or block and creating much more work. For that reason, we looked to the available bolt-on power-upgrade fare and discovered Rubicon Express's bolt-on 62mm replacement throttle body.
The Rubicon Express throttle body is made from 6061-T6 aluminum and is anodized red. It features a 62mm throttle bore that delivers much more air to the engine than the factory throttle body, which features just a 60mm throttle bore. The unit is almost ready to install right out of the box and only requires transferring the stock MAP sensor, the TPS (throttle position sensor), and the IAC (idle air control) valve and housing assembly. Rubicon Express supplies a new gasket for the IAC housing and also the correct Torx bit driver so you'll be able to remove the factory-installed tamper-proof screws.
The 62mm throttle body is available for '91-and-later Jeep 4.0L high-output engines and offers a quick and easy installation that can be accomplished by most shade-tree mechanics using basic handtools. We completed the installation in about one hour, which included the time it took to shoot photos. With the new throttle body in place, we experienced improved throttle response and noticeable power gains in the higher rpm range.
In addition to its larger throttle bore, RE's 62mm throttle body is manufactured from 6061-T6 aluminum and features an improved bearing and blade design. It's designed to bolt in place of the stock throttle body and can be used on most stock engines. Engines with a high-flow air filter will experience even greater benefits. | 
To begin the installation, we removed the K&N intake tube and unplugged the factory wiring to the throttle position sensor, the MAP sensor, and the IAC sensor. The throttle-body bolts were then removed and set aside, and the throttle and automatic-transmission cables were also disconnected. | 
With the stock throttle body removed, we set aside the gasket and cleaned up the gasket surface on the manifold. |