93 4runner with check engine on

[stevenmagnolia]

I am getting codes 14, 25, and 26. I have a 93 v6 4x4 5spd 4runner with 140k miles. The check engine will turn off after a couple of days then reappear in a couple days. When it is on the idle drops down to about 500 and it runs like crap (it feels like theres a miss, and acceleration is very slugglish) through all gears and rpms. When it starts to run normal again the check engine goes away shortly after. Any thoughts on the culprit?

Also, where are the o2 sensors? I was told theres 2 but have only found one(almost directly beneath the driver side door).

 

[stevenmagnolia]

Any ideas anyone? Is there a way to test o2 sensors ?

 

[fourwd1]

What do the codes 14, 25, and 26 mean ?

The other O2 sensor should be on the down pipe from the manifold.