So I have this, Civic I bought about 3 months ago as a project, I blew the motor on my Focus and now it looks like it now will be my daily, at least to and from class. (Less than two miles) anyway, it was driving fine for the first ten miles, it has a proper tune, B16a2 swapped, no expenses were spared in the swap, the motor was rebuilt, the head was rebuilt, the transmission was rebuilt, everything has less than 60k on it according to the previous owner, he filled the car about a quarter tank to get it to my house when I bought it, anyway, the car started missing about 10 miles into my first test drive, it would rev up to about 3k, cut out until around 1k, back to 3k and go back down to 1k, keep in mind it ran fine before this, just a little rich, anyway, my friend and I got the car up on the lift, looked for any obstructions in the fuel lines, nothing there, throwing no codes at idle, but then we discovered if you keep it at a steady 1k-2k rpm CEL would come on for O2 sensor #1, after further inspection we found that not only were there no O2 sensors, the holes were plugged and there were no pigtails for an O2 sensor to connect to. so, we plug up the Hondata, check the O2 sensor and it says it is getting a constant 3.55-3.57 volts. My question is, would there be any benefit to removing BOTH O2 sensors?? It seems so stupid to remove both, but the car ran fine for 10miles, hondata says that fuel wasn't being increased or retarded, so what could I do about this?? Re-install my upstream sensor? Please help, I could find nothing on this and very badly need my Civic running...

 

O2 sensor is there to make sure that combustion is well and efficient. Do not remove these. When the car is not hot enough the O2 sensor is not operational happens when you first start your car for few minutes and then the fuel consumption is not ideal (rich) .. when the O2 sensor engages it makes the mixture air/fuel most efficient and correct.

 

Some things that come to mind:
1) If you're saying there's no oxygen sensors, but the ECU is reading a voltage, some wire is being tapped to simulate the O2 sensor, which can be disastrous, especially if you're running on a stock ECU. I'd try to figure out where you're drawing a signal from ASAP. Perhaps you may have O2 sensors attached to the wiring harness, just that they're not located in the exhaust (unlikely, but possible).
2) It is possible to run a car without O2 sensors. You'd have to tune it really well in open loop the first time in order not to run into any issues though (my motorcycle is running full open loop without any O2 feedback). If you're on a stock ECU, then you're not tuned/optimized on open loop.
3) Perhaps you have another sensor going out to cause the issues that popped up. Either way, you have a mickey mouse job to straighten out.