2.3L ('83-'97) Help! Oxygen sensor failing and going wild

[Eduardo.lodela]

I just checked the oxygen sensor on a 1988 2.3 liters and it's going wild, ha! I'm not sure if I just need to replace it or if it is telling me something's wrong though. Any help would be really appreciated. Thanks in advance

This is a few seconds after I turn the engine on:

Shouldn't the reading go up and down?

The two white wires are ok: one shows -12V and the other shows +12V

 

[RonD]

O2 sensors are the only sensors that wear out on schedule, 12 years or 100k miles and they are no longer reliable

O2 sensors only work when heated above 600degF
So O2s have a built-in heater which is what the 12v and ground wires are for
The other 2 wires are the sensor part
O2s generate their own voltage in the presence of Oxygen, once they are HOT enough
0.1v high oxygen
0.9v low oxygen

1 of the O2 wires is a ground reference hooked to computer's "signal reference ground" that all of the other sensors use
Then the other wire is the voltage back to computer, again once O2 is HOT enough

An 1988 O2 may only have 3 wires, in that case the Ground for Heater and O2s sensor are shared, so common ground, and a 12v key on Heater wire and a O2 sensor wire to computer

If an O2 sensors age is not known then replace it, most other sensors have related sensors so computer can ID if one sensor is "out of range" by looking at the other sensors
O2s are the only sensors that have no checks the computer can do, unless they fail outright
So an older O2 can have you chasing your tail if its on its way out but not dead yet, lol

 

[Eduardo.lodela]

Thanks a lot, RonD.
I waited for a while to let the engine get hotter and checked the sensor once again; it seams to be working!

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What’s your opinion? Thanks again

…by the way; now I have steam coming out from the AC vents and seems there is some antifreeze leaking

 

[RonD]

Yes, 0.39volt O2 would be good for running engine


Your heater core has a leak, but not hard to change on pre-1995 Rangers
First check the 2 hoses at the firewall, if one leaks it can spray coolant into the opening in firewall so same symptom of a leaking heater core

Google: heater core replacement 1988 ford ranger
There are a few videos

If you don't need the heater at the moment you can remove the 2 hoses at the firewall and connect them together, so by-pass heater core and no more leak, well whats left in it will leak out, lol

Or you can "loop" one of the heater hoses, so remove one hose completely and connect the remaining hose to other hoses nipple
You can't block these hoses as its the water pump by-pass so will cause odd overheating issues

 

[Eduardo.lodela]

Thanks a lot for the O2 sensor and the heater info!
I’ll do it. It’s seems to be an easy task and the heater core is just $30 USD at Autozone