I just got a new cat converter, and there is a threaded hole to put some kind of sensore in. My car now has strait pipe with no cat, and I need to put this new on on(long story). So on a 89 civic si, is there usually some kind of sensore in the cat converter that is screwed in to it?

 

it's for an air pump or the 02 sensor. Alot of cars run them there. run down to where you bought it and buy a plug for it

 

for o2 sensor.

 

use a spark plug non fouler. get the one that is the same size as you o2 sensor i think that is hat it is for . the non fouler will have a little hole in it, i just filled it with jb weld. hope that helps.

 

Depending on its location most likely its a O2 sensor hole.
Before and after its O2 sensor
hole in the middle its a air pump connection

You can plug it with a K&N O2 sensor plug or Walker Dynomax 02 sensor plug

good luck