Identifying O2 sensor elbow in S13 SR20 Blacktop

[samadam43]

Hey guys. I just picked up a 91 S13 with SR20DET S13 blacktop. Running 12 psi with basic bolt ons and FMIC. I'm loving this new beast! But I've got a small issue...

Suddenly I have been gettting some misfiring (sputtering) at partial throttle at around 3000-4000 rpm. However, it runs fine at W.O.T. After doing some forum searching, changing spark plugs (which were very black!) I realize it is probably a bad primary O2 sensor.

Now I would like to change this thing out, but I have no idea what type of O2 housing (elbow) is in there. It looks like stainless aftermarket piece?? Could you please make your best guess as to which O2 sensor will fit in this thing. see pic below.

Also, I'm assuming this motor has primary and secondary O2 sensors, but could someone tell me where they are both located?

[Warped]

well thats definately the sensor one and if you look under your car right after the cat kinda by the exhaust mount that bolts to the transmission you'll find the other one.

take it out and take it to a parts store im sure there is a bosch replacement if that isn't a bosch already

[drifter_for_life06]

several parts dealers that sponsor NICO i believe sell factory 02 sensors

[otterman]

It does look pretty clean to be a stock one or maybe it's been replaced before. I know mine was all nast when I replaced it with a Megan Racing extension.

[drifter_for_life06]

the outlet itself looks far more "broad" than mine, and doesnt look like its cast...leading me to believe its an aftermarket one

[samadam43]

Yeah, its def not a cast piece. So, I guess my new ride has more mods than I thought... Everything but LSD of course... which should arrive tomorrow

Thanks for the input, I found the OEM O2 sensor at http://www.240sxmotoring.com for $95.

Pretty sure its the "fatty" type i need for the black top S13 sr20.

[jt15833]

my 95 (obd1) 240 only had the one at that elbow i think only obd2 240's have 2 o2 sensors

[karmakaze]

I have the O2 sensor off of a 96 Z32 installed in my car. It has a blue instead of white wire, but it plugs in and works fine.