2 wires broke off my oxygen sensor plug on the truck side (male) I took it out, butt spliced it and passed smog, but now it's running rich and I've learned that's a no no. What is my next step? i was told I must use the plug and can't make a solid connection by soldering it?

'89 4x4 22re

 

Who told you you must use the plug, I can't see any problem with just soldering the wires together, except that you'll have to cut and resolder them if you change the sensor. The plug on the truck side ties into a bigger wiring harness and would be a pita to replace. The only way to do it economically would be get a new plug, cut of the old one and solder the new one on. That doesn't seem much different than just removing both plugs and hardwiring the sensor.

 

X2. Mines broken so I used spades until I get a new sensor (then I will get a new plug too).

 

the pre OBDII O2 sends a signal to the ECU which the ECU reads as either 'rich' or 'lean'. When the O2 sends a 'rich' signal, the ECU leans the mixture, and when it sends a 'lean' mixture, the ECU enriches the mixture.
The accuracy of that signal is highly dependant on the length, and consequently the resistance, of the wires to the O2 sensor. That is why you were told to not use butt-splices. On the other hand, the ECU will adapt. If butt-splices got you to pass, there is no reason to not solder the connections. Actually, butt-splices will corrode and affect the readings so you should solder them, and protect the splice with heat shrink as well.