Alright well i'm having a little issue with the above topic. I recently cracked my headers all to **** by a pothole and was forced to replace it. I bought a DC header and put it on but there was not an o2 bung on it. My car is obd2 and i know that it needs two but, i'm using a P28 instead. I still have one on the cat but it runs like complete ***. Only in low rpm's it seems to bog down, then it gets going like it should when i get past 4,000 rpm. Now i'm confused because obd1 ecu's look for only one o2, but the obd2 ecu looks for two. So when i hooked up the obd2 one it popped a Cel 41 as i don't have the Primary O2 hooked up. I didn't have this problem with the old header, with either ecu hooked up. Any idea's as to what it could be??

 

i assume you using a jumper harness to run a OBD1 ecu with the OBD2 harness.

the primary O2 sensor controls your air/fuel mixture. the secondary monitors catalysis efficiency. you need a primary O2 in the header. yes the p28 only looks for one, but it knows the difference. you need to have the correct O2 plugged into the correct Plug. with the p28 you dont need to run the O2 in the cat because it does not use it.

if your header does not have a bung on it then you need to have one welded into it.

 

Okay good deal. I was worried about having to do that before i put it on the car. Oh well, give's me something to do. Thanks for your input