You need a scan tool to check close mode is enabled or not.
Don't trust many posts here or anywhere saying close loop is enable at engine temp above x° etc.
Depending on ECM PROM Programing...
ECM can run Close Loop as soon as O2 is warm enough to operate. (Scanner reports Oxygen Sensor = Ready.)
Can be in < 1-2 minutes of engine run time.
87 and up DIS L4 goes Close Loop very fast even when ECT and MAT says Engine is cold.
V6 could take longer to heat O2 sensor because is farther down the exhaust.
And Don't confuse Close Loop and Learn Control... Very, very short story... Is Not same thing.
Learn Control on/off depend on condition of BLM and Integrator.
Testing... Still Need a scan tool. Even if Sensor test good using Volt meter or just replacing the sensor, bad ground(s) or O2 wire can cause ECM problem to read the sensor.
See my Cave, Scan Tool Help
and rest of section.
Most times, running rich is cause by iffy injector(s), bad seals, or bad plumbing/regulator causing high fuel pressure.
High fuel pressure can kill Fuel Pump. Fuel Flow is Coolant for the pump. High pressure often restricts flow...
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)