I have a '95 4Runner with the check engine light on. The car also has a rough idle. After checking the computer for codes, I got codes 25 and 26. My Haynes book has these two diagnosis: 1)When the air-fuel ratio feedback correction value or adaptive control valve fedback frequency is abnormally high during feedback condition. 2)Open circuit in oxygen sensor signal (Ox).
For trouble areas it suggests checking: 1)Injector circuit, 2) Injector, 3)Fuel line pressure, 4)Oxygen sensor circuit, 5)Oxygen Sensor, 6)Air flow meter, 7)Water temperature sensor, 8)Cold start injector

A friend who works on cars a lot said he's sure it's the oxygen sensor. I know I can buy an OEM O2 sensor at this website for about $100: http://www.1sttoyotaparts.com/part_number.html

My question is do you guys agree with my friend and just buy the O2 sensor or should I be checking some of those other things out first.

Yes I am pretty sure your oxygen sensor is old and lazy,besides they should be replaced every so often:

http://www.toyota-4runner.org/showth...threadid=34336

You can test and the troubleshoot the oxygen sensor and it's circuitry by using the factory service manual:

http://www.toyota-4runner.org/showth...threadid=34326

Sidney

Thanks Sidney, I just ordered one today from 1sttoyotaparts.com, it ran me $105 with shipping. It seems easy enough to replace, just a few 14mm bolts and then just unplug the o2 sensor right? thanks again

It should be free shipping with orders of $100 or more with them. On my 1985 4-Runner yes it was two 14 mm bolts on my 1995 4-Runner that I bought 3 weeks ago I don't know but the free factory service manual download links I provided have a free 1995 4-Runner manual and should show you. Again spray the nuts with any of those deep penetrating lubes hours or a day prior to removing them.

Sidney