Runnin rich

[yj9340]

I just installed a new tailpipe less than 200 miles ago. After tearing apart the jeep and piecing it back together. Anyways the tailpipe is already pitch black inside. I have the 4.0, and just did a tune up this summer when I had it all apart. The O2 sensor is less than a few years old.
any thoughts?

[Ramrod1]

I'm no mechanic but...... I was running a 180* thermostat during the summer and found that my 4.0 was running rich. It had more pep in it's step, but the intake manifold runners were wet with fuel when I had it apart.

[Ted_Grevers]

I would check your O2 sensor again. Even new ones can fail, yours is a couple years old, and may be bad.

I would also inspect the wiring of the O2 sensor; burned or frayed wires can cause a partial failure. On my ZJ, the rear O2 sensor wire was frayed, and caused mine to run rich.

-ted