Weird oscillating AFR reading and high idle

[DrSatan]

I'm new to Hondata and tuning and recently put a P28 S300 in my 1992 Civic Si with an OBD1 B16A. Car feels great but I've got something weird going on with the AFRs and idle. I loaded the stock P30 EG6 map and turned off the knock sensor. TPS is set in Smanager and timing is also set perfectly.

I noticed that it runs super rich and the AFRs don't change if I adjust the fuel trim in either direction. I went up and down 5, 10, and 15% in the fuel trim and no change to AFR whatsoever at idle. However, it felt like it ran super smooth and had more power at -10% fuel trim.

Also, the idle is a little high at about 1100 even though its set to 850, and the idle also does not respond to any idle changes I make in SManager. The idle oscillates up and down about 50 rpm or so, barely noticeable, and the AFRs oscillate from 10 to about 12 along the same rhythm as the RPM change at idle. When I'm cruising in the car, the AFR is about about 10.6, and when I let off the throttle and go into engine braking, AFR goes somewhere below 10 (my AFR minimum and limit is set to 10 and 18 in Smanager), so the injectors are not doing the deceleration fuel cut, which I don't know if that might be a setting in the Smanager. I'm using the stock o2 sensor and replaced it with another new Denso sensor (234-4099) because I thought the old one was behaving like the failing o2 I had in another car, but no change. Stock o2 sensor is selected in Smanager.

Aside from changing the o2 sensor, I looked for vacuum leaks and did a smoke test and all is good. My EVAP is deleted but everything is capped. It's a very OEM setup, stock exhaust manifold, stock intake, stock vacuum setup, nothing weird. No codes being thrown. All genuine OEM sensors except for TPS.

[Spunkster]

Do you have a wideband?

[DrSatan]

Do you have a wideband?

No wideband. I assume I am using the factory o2 sensor to get those readings..

[Spunkster]

You cannot use a narrowband to properly read AF ratio.

[DrSatan]

You cannot use a narrowband to properly read AF ratio.

Okay, thanks.