89 4runner efi 22re Another CEL Code 25/26 Problem (1 Viewer)

Feb 25, 2009
Hello everyone, got another CEL diagnostic problem with a 89 4runner 22re efi. It is popping up the 25/26 codes, lean and rich. I have read numerous posting on the internet about it and am still kind of stuck. Any help would be greatly appreciated. I have tested:

MAF - Resistance readings in spec
TPS- Resistance readings in spec
O2 sensor - reading .7 at idle and .9 at 2500 rpm
Compression test all 90psi except for #3 which is 120psi
Air leaks - found a few, vacuum lines and manifold but still threw codes
Cold start valve
EGR- went to smog and this failed, (EGR Functional test) But I fixed it and it is operational - had a clogged port
Air Flapper valve works
Has great spark to all plugs
Replaced cap/rotor/plugs/wires
New alternator, battery
Might be losing a bit of coolant
Burns around 1/2 quart per 2000 miles maybe
Leaks Coolant out from somewhere near the starter.

Smog test1: rpm 809, CO2%=13.3, O2%=2.3, HC=187, CO%=.01 - Fail - Max HC=120
Smog test2: rpm 2649, CO2%=12.9, O2%=2.9, HC=370!, CO%=.01 - Gross Polluter - Max HC=180

I have not tested/checked:
Fuel Pressure
Fuel Filter
Leakdown test
and a lot more

Any thoughts? Might be head gasket? Valves? Rings? Just bought it from a guy who said the head was "done". I need some frickin oil to pour into cylinder to see if it is the rings, can't believe I don't have any. Thanks for any input!


Just spend all the money.....
Jan 8, 2006
Fallon, NV
I think the 25/26 code usually means bad O2 sensor... To really check the sensor, you need either a needle multimeter, or some fancy machine.. I can't remember... The sensor is supposed to oscillate between 0 and 1 like 10 times a second... I think...

Welcome to Mud! :flipoff2: We're gonna need pics.... :D
Feb 25, 2009
Cool, I checked it with my crappy multimeter and it was changing about 2 times a sec or so, was .7v at idle and .9v at 2500rpm. Running rich. 0 is lean and 1 is rich so it is really rich. The emissions test showed it too, idle was a little cleaner. I did the leak down test and there was a decent amount coming out the intake tract to the air filter. A little blow by through the rings and out the motor oil fill cap, nothing going on in the coolant - though the thermostat wasn't open if that matters. Maybe the intake valves are tight or leaking? I might pop the valve cover to check the clearances. It was hard to start with the #3 cylinder getting the pressure test, also had the highest, doing most of the work? Thanks for your help!
Sep 14, 2005
The NW, Cascade Mountian Range
that link sounds believable.
in all the datastreams i look at when using my snap on modis, the values of a higher voltage indicate lean.
infact, that link states voltage fluxuates between .1V to 1.0V. I often see some as high as 4.8V
Feb 25, 2009
Anyone have any suggestions? I have a lot of info posted and maybe there's a red flag somewhere. The compression check was done inaccurately. There is a really rich condition. Thanks for any suggestions!

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