I have a 200 civic lx. Just installed new reactive 4-2-1, 2 peice headers. The new headers have the two ports for both of my o2 sensors, which is where I put them. Now my check engine light has come on and my engine seems to be running badly. The cats used to be between the o2 sensors and now there is nothing. I think that is the problem but I need to find out how to fix it.

 

Try switching them, I had to on my B16a and it ran better. Where were the stock ones located and where are these located now? If you got a ceramic coated header, and the o2's are on the bottom of it, they might not be getting hot enough.

jB

 

would this be why im still getting the code 1 and 2 (o2 sensors)? i have type R headers in a b16 crx and i relocated the o2's from the top of the header from my stock manifold to the downpipe on the type r header.

 

it shouldnt matter, mine was located right at the collector for my stock motor and after my swap it moved to 2 inches from the cat. no problems
switch the o2 sensors, if that dosent work you may have damaged one.

 

When I moved mine down, they wouldn't get hot enough for my B16a1 to register them, and would constantly throw the code. Try switching them and see if it helps.

 

what header are you guys using that fits a b16a1 and takes both O2 sensors?

 

You should have gotten a check engine light since you removed the cat. (LX has a close-coupled header-cat combo if I remember).The primary O2 sensor monitors air/fuel whereas the secondary O2 is primarily functioning to measure catalyst efficiency. If you look a the signal from the primary O2, it is a quickly moving sine wave. If you look at the secondary O2, the signal switch time is much slower because of the differing exhaust content. With the cat removed, there is no longer a difference in the signal between the sensors...they are just a foot apart... giving the same signal. The ECU sees that catalyst efficiency is now Zero and sets a code for the CEL.
We have used the EX header, Cat, and Catback (as a complete system)...relocating the sensors on quite a few cars and have had no problems. Sometimes you can run into issues with distance problems but that is normally due to a "slow" O2 sensor that may have quite a few miles on them.