Yo topless92,
Welcome!
I can see that you have a very good handle on troubleshooting.
Did you check for vacuum leaks in the HVAC circuit too?
I have a vacuum leak diagnosis here in post #20 @
http://broncozone.com/topic/23994-90-58l-getting-continuous-code-33-and-running-code-44/?p=125535
DTC 42; Engine Not At Normal Operating Temperature during Code Test.
O2 sensor voltage was stuck high for too long. (Rich).; "...Bad O2, or it's connector/wiring bad, Bad fuel pressure regulator, pull vac hose off, any gas in it or gas aroma means it's bad (ruptured diaphram); Leaking injectors, restriction in fuel return line or exhaust leak or clogged exhaust, lowering vacuum..."
DTC 41, 42, 85 OR THREE DIGIT CODES 171, 172, 173, 179, 181, 182, 183 & 565 are received , Check for proper HEGO Ground; in Catalytic Converter Diagnosis TSB 91-12-11 for 86-91 Bronco, F Series, & Econoline...see below wiring diagram;
by Ford via Stephen
...
Wiring Diagram in a 90 by Ford via Seattle FSB
Ground G101 (aka power ground) is @ G101 RH side of Radiator support
Ground G103 is @ LH rear side of engine near knock sensor. Is OK.
More locations in a 90 from 90 Bronco EVTM for future reference; "...G100 LH side of Radiator support; G101 RH side of Radiator support; G102 RH side of Radiator support; G103 LH rear side of engine near knock sensor; G104 LH rear side of engine compartment, near electronic engine control (EEC) module, on the left fender close to the firewall; G105 LH Side of engine; G106 RH fender apron, near voltage regulator; G107 RH fender apron, at starter relay; G108 RH fender apron, at voltage regulator; G109 RH fender apron; G201 LH rear side of I/P (looking at the diagram it is at the bottom of the driver's side dash assembly. Screwed to the bottom edge, just to the left of the steering column. It is the ground for the instrument cluster); G202 Behind RH cowl panel; G203 RH rear side of radiator support; G204 On steering column; G205 Behind Center of I/P (Dash); near speed control amplifier; G400 LH side of cargo area; near rear light assembly; G401 Below LH side of cargo area; near crossmember; G500 Inside driver's door; near left door speaker"
Source: by BroncoJoe19 (Joe) at Ford Bronco Zone Forums
...
EEC IV CONNECTOR PIN LEGEND
http://web.archive.org/web/20120118104425/http://www.oldfuelinjection.com/truckpinouts.html
&
Pin Diagram
http://web.archive.org/web/20120115055624im_/http://www.oldfuelinjection.com/images/eec05.gif
by Ryan M.
If the other HEGO grounds are good, the following areas may be at fault:
* Ignition Coil
* Distributor Cap
* Distributor Rotor
* Fouled Spark Plug, are they showing rich condition?
* Spark Plug Wires
* Air Filter
* Stuck Open Injector
* Fuel Contamination
* Manifold Leaks Intake/Exhaust
* Fuel Pressure
* Poor Power Ground
Although you inspected wiring from O2 to PCM, I will leave following in:
Look for Poor mating of the connector halves, especially if the locking tabs are broken, which occurs with our elderly Broncos.
Terminals backed out or not fully seated in the connector.
Damaged terminals or poor terminal to wire connections.
Corrosion or water intrusion. Pierced or damaged insulation can allow moisture to enter the wiring causing the conductor to corrode inside the insulation. Look for swollen and stiff sections of wire in the suspect circuits.
Wires that are broken inside the insulation.
Pinched, cut or chaffed wiring in the harness.
Look for unravelled or missing harness wrapping and loose harnesses where PO pulled harness from its straps, and/or clips.
Wiring that is damaged as a result of being in contact with exhaust components, such as the O2 sensors, CANP solenoid where it's hose is known to melt on exhaust manifold.