I have recently replaced the headers on my civic. It is a 98 4 door lx. The engine is a 1.6 1-4 D16Y7. The way the setup works based on my engine I can't leave the stock cat on there. I have put the headers straight into the exhaust piping and replaced the entire system.
However, my CEL is on i guess because it senses that there is not a cat. Is there a way to get this light to go away ? I'm also trying to make sure my fuel mixture is not rich or lean because I don't want to cause major engine problems. Is there a way to fix this ? There aren't any emissions tests where I live so I'm good from that standpoint. I am just trying to make sure that my engine is running like it is supposed to. Thanks!

Do you have 2 O2 sensors? I've heard of people splicing them together or using a "02 simulator" for the non existing after cat bung that you essentially eliminated.

Yeah It does have 2 02 sensors but you can't splice them together because they are supposed to have different readings. The difference between the first and second measures the efficiency of the cat, but I don't have a cat so thats what I don't know how to fix. The muffler shop said they could put another 02 sensor bung on the front of my headers for the other sensor but I'm not sure if that will fix anything or not. I'm just trying to keep my engine from running too lean and burning a piston. Thanks

You probably won't run lean. Hondas are tuned to run rich and if a CEL pops up they run really rich.

I suggest you have a test pipe fabbed up by the muffler shop with a bung for the 2nd 02 sensor. Then after that, if you are not going to get a whole new exhaust, have the muffler shop fab up a new connector flange to bolt onto the fabbed up "test pipe" or just have them weld it all together. I wouldn't have them mess with your brand new header though.

Yeah well the headers I have don't have a test pipe, they're racing headers so its a header and then a Y rocket down pipe or head pipe. I'm not going to have them drill into that, I think I'm just going to leave the front sensor hooked up and then buy a sim for the back one. It has been running rich because you can smell the gas in the exhaust. I actually am having the rest of the exhaust done, 2.25 with resonator and glasspack. Why would that make a difference though ?

A test pipe is in place of a cat. On a set up whereby the cat is NOT in the engine bay a test pipe simply replaces it. It's just a phrase. And your race header (not headers... you only have one head) eliminates the STOCK location of the cat. Just have the muffler shop put a bung after the header on the new pipe that they bolt to your new header or better yet, put it after the resonator (which essentially will be where your cat would be if you put one back on your car). Then add your fart can on the rear. FYI - a glasspack is more of a resonator.

www.o2simulator.com (http://www.o2simulator.com)