New cat has no O2 bung

'96 4.0 AW4 242 3" lift

Picked up a new muffler & cat and was installing today and find that the cat has no bung for the O2 sensor.

I have read that the downstream sensor only checks for Cat function.

Can I just disconnect it without affecting the fuel mixture or is it actually needed?

I don't mind setting the engine light and I don't have any emissions testing coming any time soon. I figure when I need testing I can pop a new hole between the cat and muffler - but I just want to get it back together right now.

Re: New cat has no OS bung

You should be fine. You will get a check engine light, but you can drive it to get a new o2 sensor bung installed.

Re: New cat has no OS bung

Yes the first o2 sensor checks how much oxygen is left from the combustion cycle, telling how rich or lean the engine is running. The second one just tells you how well your cat is working, has no real affect on how the engine runs. You will be fine, but it will probably throw a code real soon.

Re: New cat has no OS bung

I had a related problem (sensor threads destroyed themselves on the way out) and I let the sensor 'swing in the breeze' on a 1998. It never threw a code, strangely enough.

About 8K miles later I bought a new sensor, removed the Allen-head pipe plug and put it in. The downstream sensor only verifies cat function, doesn't affect A/F ratio.