I have a little ques hope someone can answer. I was originally was gonna put a header on my car and nothing would bolt directly to the stock exhaust. I ended up taking off the stock manifold and noticed it had a catalyst in it. The catalyst was all shot to hell and looked like toast. I ordered a replacement manifold from Dorman, but those did not bolt directly to the stock flange either. So I ended up removing the catalyst out of the manifold and put it back together. I still have a cat after the stock flange. I notice more power out of the car and it sounds alot better too. I have a magnaflow muffler and cold air intake too. The problem is the check engine light is on and get a 420 code. Catalyst is under efficient or something. My friend and I think that if we put the 2nd O2 sensor behind the other cat it will satisfy the computer. Anyone think that is a good idea.

 

I don't get it? You removed the internals of the catalytic converter, and are surprised the CEL came on because the catalytic converter isn't "working" correctly? What would a second O2 sensor do exactly? It still won't read in-range for the computer...

 

Nooooo. I had a feeling it would come on. The catalyst is in the manifold, like its a one piece type of deal. The O2 sensors are before and after the catalyst. The catalyst was burnt out anyways inside the manifold, so we removed it. Now if I put a header or any other type of manifold I would get a CEL anyways. What I am asking is the the first O2 measure what comes out of the engine. The 2nd one is after that stupid catalyst. Why dodge did that is beyond me. What I am asking is if the downstream O2 is after the other Cat on there it should satisfy the computer, if not I will have to get a modyfied computer.

 

Oh, OK. I think you can actually get a spark plug fouler and put the O2 sensor into that. It will pull it up out of the direct exhaust stream. It is a somewhat common mod around here; it isn't 100% guaranteed to work, but is the cheapest method to try and take care of the light. how too trick your computer if no cat

As for O2 sensors, try 4 on the V8 Mustangs (2 before and 2 after the cats)! Easier problem to fix though I suppose. Just shut the rears off with a hand held tuner.