94 FZJ code 26 running too rich

[93yotasr5]

unless moisture from the heater core got to one or some of the wires. hence why my issue is intermittent. steam from the core may have corroded a wire or something of the like. I just found a local heater core from a friend. Hoping to replace it next weekend. I will be checking all of the surrounding wires when I do so.

 

[HiluxFZJ88]

A leaking heater core onto wiring could definitely cause an issue. I was unaware that any of the engine harness went near the heater core though. I'll have to look under the dash and trace it. I've had new O2's relocated into the manifolds for a week or so. Runs smoother, more power and better MPG.

 

[40LandCruising]

I had the exact same issue as @BlackLS1 and it was out of nowhere as well. Following the advice of @landtoy80 I unplugged both my O2 sensors and now it runs perfectly. I just replaced both sensors 2mo ago and am confused as to what the issue is here. I have no problem with running without the sensors connected, I just would like to get rid of the CEL.

 

[Underdog]

Just to add a data point here, I had code 26 only with no code 25 and it turned out to be the oxygen sensors. I checked their voltage and one seemed to be good and the other the voltage was way too high around 7 volts. Truck would idle really rough but drove OK. It's a '94 with two O2 sensors pre-cat. No sensors after the cat. I have 312K miles. Doing research here it appears each O2 sensor reads 3 cylinders. Since one was within range and appeared to be sweeping thru the range normally I ruled out anything common to all cylinders like the AFM. Got the O2 sensor kit 89465-60110 from the dealer and replacement was fairly easy although its tight trying to get a wrench on the O2 nuts.

 

[Reginherus]

Stale thread but figured I throw this out there in case someone is troubleshooting like I was. Engine has 269k on it and I got a 26 and a 71 code, so Rich A-F and EGR system fail. Idle was rough, hunting from 600 rpm to just below 400 rpm at light with AC on. Cold idle at start was over 1000 rpm. The idle was my biggest issue. Old enough now I don't have to worry about emissions, but I cannot stand a CEL light on the dash.

My local LC shop had said my canister was almost gone. So, tried installing a used eBay special -- no luck. Took my original canister and went the refurbish route: Cut it open, replaced the charcoal with fish tank filter charcoal, cleaned the check valves with carb/choke cleaner and re-assembled with Red RTV. Lifted the battery to clear everything and came back up smooth as I've ever seen it. CEL is clear.

Been back and forth with PO (my Brother) if he ever changed the OxSensors ... he cannot recall and it's not in the records he gave me.