High Flow cat problem......
 

My girlfriends car is a 1998 Honda Civic EX 2dr coupe, it has a 4-2-1 header on it, a high flow cat and a catback. The problem is that there isn't an O2 sensor hooked up to the cat (universal kind without any O2 sensor wholes), and she has to go for emission testing soon. I know I have to make a whole and weld in a bung, but I dont know where to weld the bung for the O2 sensor. Should it be before the cat (by the two bolt flange)or right after the cat?

RE: High Flow cat problem......
 

right after the cat...

RE: High Flow cat problem......
 

Should be two O2 sensors, one before the cat and one after.

RE: High Flow cat problem......
 

There is one in the header, so the second one that I need to put in should go after the cat?

RE: High Flow cat problem......
 

Thats what it sounds like when I read it.

RE: High Flow cat problem......
 

Yep, after it.

RE: High Flow cat problem......
 

Awesome thanks guys

RE: High Flow cat problem......
 

Try to keep it as close to the cat as possible though, you'll get better readings.

RE: High Flow cat problem......
 

youre sure its a high flow cat not a test pipe?

RE: High Flow cat problem......
 

I pretty sure it is a high flow cat, from what I gathered everything was purchased from ebay from the header to the catback and including the highflow cat.