hello I have 91 onda civic dx with and D15b in it trows a code for o2 sensor so I replaced that checked the wiring that's good I also replaced the cap and rotor and also the coil and plugs and wires problem is still there. today driving to work like half the power was gone. I also cleaned the IACV. I have no idea what to do next and it need it running good cause it gets me to work. it seems to just do this when it warms up. I have a high idle and sometime the idle pulsates.

 

So do you have an actual D15B, and in that case which one?
Or do you have the D15B2 original to the car? IF you have the D15B2, then it's likely one of two things - bad wiring, or the O2 sensor is ok and sending a bad reading.

If it's wiring - check all grounds up front first. That's probably going to be an issue eventually anyway, worth a look. When you say you checked the wiring, did you visually inspect or did you perform full continuity tests? Don't just check for continuity, check for resistance as well. That's really the only way to be absolutely sure.

If all of that's fine, then your engine's running wrong and the O2 sensor knows it. Fuel injectors are your likely culprit on a dual point. They develop issues eventually and start seeping fuel, so you run rich especially at start. Mine did this, solution was to go multi-point.

And if it really is a D15B, then half of this is worthless, but at least you can still check your grounds!