1997 Jeep TJ - Throttle Body Upgrade - Off-Road Tech

1997 Jeep Tj Throttle Body Upgrade Butterfly Plate

1997 Jeep Tj Throttle Body Upgrade Throttle Body

The Jeep 4.0L engine found in TJs, XJs, ZJs, and WJs is a trusty powerplant, and the '91-and-newer high-output versions make respectable power for a long time if well cared for. We recently ran across an easy mod that can provide a quick power boost and help renew an aging throttle body on these engines.

The stock throttle body bore is 55mm and a common upgrade to increase intake flow, and ultimately power to the wheels, is to bore the aluminum body to 62mm to match the diameter of the bore in the intake manifold. Combine this with a free-flowing air cleaner and muffler, and you can unlock some performance for not a ton of money.

Jeepers and Creepers in San Francisco, California, has been boring the Jeep throttle bodies for almost 10 years so they know the 62mm bore mod is a valuable upgrade. However, they started seeing the results of aging throttle bodies: housing cracks and wear at the throttle shaft bearings (which can result in leaks and poor idle).

They solved all these issues by introducing a billet machined throttle body bored to 62mm that is a bolt-in replacement for the stock unit. We performed an install on a stock '97 Jeep TJ in about an hour and a half and also dropped in one of their new throttle body spacers while we had the induction parts off the engine. Here's a brief tour of the install.

1. We removed the air intake tube to access the throttle body. Next, the sensor connectors and throttle linkage parts were removed before the throttle body was unbolted from the intake.
1. We removed the air intake tube to access the throttle body. Next, the sensor connectors
2. The manifold absolute pressure (MAP), idle air control (IAC), and throttle position sensor (TPS) were removed from the stock throttle body. These are reused in the new body.
2. The manifold absolute pressure (MAP), idle air control (IAC), and throttle position sen
3. You can purchase the replacement throttle body with a brand new throttle shaft as shown here. Or, you can save a few bucks and reuse your shaft after making a few small modifications with a hacksaw and metal file. We applied a little grease to the shaft and bearings in the body before installing the shaft.
3. You can purchase the replacement throttle body with a brand new throttle shaft as shown

4. The new butterfly plate was screwed down onto the throttle shaft, while ensuring it was centered in the bore of the new body. Pay careful attention to this step as the plate should fit the bore snugly but not bind as the throttle is opened. The MAP, IAC and TPS were all installed on the new body as well.
4. The new butterfly plate was screwed down onto the throttle shaft, while ensuring it was
5. The spacer kit includes longer bolts and sleeves to raise the throttle cable bracket so the cable continues to mate at the correct angle with the raised throttle body.
5. The spacer kit includes longer bolts and sleeves to raise the throttle cable bracket so
6. We added the new throttle body spacer onto the intake with new gaskets, then bolted the throttle body down with the new longer bolts supplied.
6. We added the new throttle body spacer onto the intake with new gaskets, then bolted the

1997 Jeep Tj Throttle Body Upgrade Throttle Cable

7. The electrical connectors and throttle linkage were reassembled. With the new spacer in place, it's a good idea to recheck throttle cable for any binding or limits to its travel.

After reinstalling the air intake tube, we fired up the Jeep and it settled to a quiet idle so we took it for a short drive. We found the off-idle response to be smoother overall and the mid-range power to be more responsive by the seat of our pants. Next up would be an air cleaner upgrade and we'd enjoy more benefit by letting our 4.0L breathe better through a 62mm bore.