I don't know much, but I am baffled. I have a pretty much stock 1997 civic hx with a 5 speed, the only aftermarket items are a header, and cold air intake. The cel was on and the code said slow response from the o2 sensor and it ran terrible. So I unplugged it and it ran fine besides terrible gas milage and the cel on. So I put an o2 sensor defouler in both of the o2 sensors and it still ran bad, it sputtered bad at about 2500 rpm. I just bought an o2 sensor off of eBay and the wires on it were about 6 inches to short, so I cut the sensors and soldered 6 inches to the new sensor. The cel turned off and it drove fine through town but at about 60mph in 5th gear it would hesitate and bog and then it would go back to normal for a minute and then do it again. I would like to find a solution to this issue other than going back to stock. So I am stumped. Any help would be greatly appriciated.
thanks in advance.

 

What did you put a non fouler on both sensors? You need to read up on what you're trying to accomplish.

The car should be absolutely dumping fuel.

 

I did put non fouler on both sensors.

 

Oh, because that's exactly what you said you did :

Anywho, the front sensor must be an LAF sensor, not the typical four wire heated O2S. I would recommend using an OEM or brown-box equivalent here, definitely not something that needs to be spliced in... the ecu tends to be pretty picky about them. The HX originally came with a close coupled cat/manifold combo a la DX/LX/CX, so you may have a hard time keeping it happy with the header on there, no matter what you do.

Start with the sensor and report back though, your bogey is most likely in that general area.