aFe Exhaust System for Jeep Wrangler TJ

The jeepfan.com 2004 TJ Unlimited has 195K miles and might have the original exhaust still on it. The check engine light had been illuminated for a bit, the code had something to do with a fault in the emissions system. It just seemed like a full replacement of the system plus all new O2 sensors made sense.

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The TJ 4.0L used a variety of O2 sensors through the years and even a variety of how many sensors. The 2004 uses four sensors, 2 small catalytic converters, 1 larger catalytic converter and a muffler. The manifold is split a the engine running three cylinders into one and the other three into another. There is a sensor in each manifold before the small converter and a sensor after each converter. It’s rather funny how each converter is a different part number and has a separate plug type.

We chose the aFe system to replace all the original equipment except the manifolds. The aFe system is fully stainless steel and the mandrel bent oversize tubes will withstand the elements while increasing flow. The converters are higher flow and the performance y-pipe provides less resistance.

So, the project isn’t terribly complex but the work is messy and in very tight quarters. Reaching way up to the manifold bolts is a real challenge. Long extensions are necessary.

Removal of the old system is the obvious first step. We started from the rear and worked our way forward. With the Jeep safely raised up to allow easy access to the bottom remove the transmission cross member. Support the rear of the transmission. Unbolt the transmission mount then the six bolts that hold the crossmember to the frame. With the crossmember removed we used a sawzall and started chopping up the old system into sections.

The final step was unbolting the y-pipe that contains the two converters from the manifold. Make sure to unplug the sensors first. The final step in removal is removing the sensors from the manifolds.