O2 sensor?? what? where? how? Pleeeez!!
 

I just bought another Rx-7 this ones an 85 it run really great and all that, but it wont pass emissions. When i asked the previous owner, he said the the o2 sensor was broken due to the recent installment of custom " Yoshimira" exhaust (if you know what that is, good cuz i dont) ne way i have a complete 83 Rx-7(doesn't run) and was told i could just switch the sensors and be ok. Unfortuneately I have yet to find an o2 sensor on either vehichle, and the repair manuals are no help either. I would really appreciate ne help in this matter. BTW this "o2 sensor" supposedly has somthing to do with a self adjusting carburator. Thanks again.

If your car is not a 1984 or 1985 GSL-SE with the fuel injected 13B engine, then it does not have an O2 sensor.
Check around back to see if it really does have a motorcycle muffler :p: (nothing to do with smog)
Do some searches on how to get your car to pass smog testing

Well, unless you have a GSL-SE (fuel injected, 13b) you do not have an O2 sensor. I am not familiar with that exhaust, but if you do not have a good cat in there, you will not pass emissions. If the cat is good, I would start with a basic tune up (plugs, cap, rotor, maybe spark plug wires, new fuel fiter) and see how it does. It could also be that the Air Control Valve (ACV) is malfuntioning. The ACV is what directs air from the air pump to the cat converter or exhaust ports. Do you know how bad it failed emissions?

The 83 will not have an 02 sensor because it is not the GSL-SE.
Yoshimura makes motorcycle exhausts. http://www.yoshimura-rd.com/default2.asp

o'2 sensor
 

First of all, there is no such thing as a dumb ? I take it this is not a gsle model with a aftermarket carb on it . In otherwords, it's not a 13b engine. If this is the case, you don't have a o'2 sensor. Ned to know what portion of the smog test you
dfailed? Was it the idle test or 2500 rpm test? If so, what are the hc readings at both idle and 2500? A rotary engine is a very dirty engine, thats why there a multiple cat's on the vehicle. Make sure the oil has been recently changed, the air filter is clean, plugs are fresh, check for any vacuum leaks. Does it idle smooth? The #1 failure for smogs on carb engines is the catalytic converter being worn out.
This is particulary true if it has the original one still on it.

Thanx alot guys! Motorcycle exhaust? WTF!!? I knew the guy I bought it from was a idiot as soon as I saw the crappy job he did shaving the door handles. That alone set me back at least a month before Ill even be able to respray the damn thing. ne way the cars with me out in the country but hes holding the title till i finish paying for the car, so he was the last one the to take it to emmissions but ill see if i can get ahold of some info on how bad it failed. I dont have much cash to be buyin cats and stuff so what might happen if i just rodded out the old ones and put them back on? This worked miracles for my 79 camaro and my 77 pace arrow motor home. just wondering if thats a good idea with a rotary. But thanks again. This helped alot.

failed smog
 

Removing the inside of the cat will do nothing for your smog test, but make it a gross poluter.. It will help in the performance category, allowing it to breathe better. A universal cat will cost you around $110-$120 installed at a muffler shop.
They can also test to see if it is working or clogged. The outlet temp should be hotter than the inlet temp.