Engine Mechanical problem
1993 Ford Taurus 6 cyl Two Wheel Drive Automatic 140000 miles

I have a 1993 Ford Taurus (automatic, V6, 3.8gl, 140k miles) that is having a weird idle/stall problem.

The idle is rough, and sometimes when I put it into gear and push on the accelerator it idles down (if my headlights are on, they dim). If I continue to push on the accelerator while it is idling down, it will die. It doesn't do it every time I push the accelerator and it seems to be worse in the cold.If it dies, it won't restart for a few hours.

I searched some forum posts and found a recommendation to clean the IAC, so I did that (sprayed throttle body cleaner through it until it looked clean). But that didn't seem to solve anything. I also cleaned the MAF sensor, but that didn't do anything. I checked a couple plugs, but they look fine. The distributor cap is relatively new (isn't cracked; not very worn). I can hear the fuel pump startup when I put the key into the on position. The air filter is clean. I also tried bypassing the Fuel Pump inertia switch, but it didn't change anything.

I got a few engine codes that may be relevant to the issue(s). The descriptions are from my Haynes manual.

KOEO (Key on, Engine Off)
542 - Fuel Pump Circuit Open; ECA to motor

KOER (Key on, Engine Running)
173 - Oxygen Sensor Indicates Rich Condition, right side
137 - Indicates Rich Condition, left side
129 - Insufficient Manifold Absolute Pressure/ Mass Air Flow Change
167 - Insufficient Throttle Position Sensor change

Any suggestions would be greatly appreciated! Thanks!