Long running problem. CEL 172 176

[awood]

So I thought I knew just a little about these 1st Gen Explorers and Rangers, but I've been humbled - Turns out I don't know squat! I picked up a 94 Explorer recently after my 92 was wrecked with the knowledge there was some existing problems. I thought I could fix it, but so far no dice. Here's what I have: The CEL will come on after a short drive. I assume it comes on as soon as it switches, or tries to switch to closed loop. Here are my codes:
KOEO 111 (no faults)
CM 172,176
KOER 172,136,176

There were a lot of issues I've already corrected to some degree. Here's what else I've done:

Replaced some damaged vacuum lines
Vacuum is rock steady at 18 inches. Sprayed starting fluid all around, especially around intake manifold. No other problems noticed.
New air filter.
Fuel pressure is about 40 after cycling key a couple of times. Engine running is 30 psi. Pressure increases if throttle is slightly goosed.
Replaced fuel filter anyway.
Replaced O2 sensors (173,000 miles)
Replaced DPFE sensor (after reading online, it seemed a high failure item)
EGR diaphragm holds vacuum, and operates when 5v applied to switch
Replaced TPS after finding a dead spot at about 2/3 throttle
Replaced Spark Plugs and Wires. You'd be surprised how well it was running with a Spark gap of .125
Cleaned Throttle Body
Drilled 3/16 hole before and after the cat to check pressure. No readings on my vacuum/fuel pressure combo gauge. Pressure zero on both sides.

Noticed Alternator output is 15V. Disconnected alternator and CEL still comes on. Also noticed that when back probing the PCM connector with the engine running, I get a fixed rich voltage at 800mV on both O2 sensors (pins 43 and 44) at any throttle setting. I'm not sure what the other side of the O2 sensor is (Pin 29). Is this a reference voltage (450 mV) I read about somewhere ?

The Explorer seems to run ok. No missing or bucking. It does seem a little lacking in horsepower, and fuel consumption seems high, but I haven't had it long enough to really tell. The exhaust is smelly, but not black. When I changed the plugs they were not fouled. The smell seems to be the sharp smell from a Catalytic Converter more than a fuel enriched smell.

Sorry for rambling on, but I'm running out of ideas short of trying a new PCM.

 

[awood]

Forgot to mention that I checked both ECT and ACT sensors. Both resistances were consistent with the charts at their temperature, but I didn't check them full range. Also, the MAF seemed to have good and smooth voltage increase on the signal wire as the throttle was advanced with the engine running.

But, as a follow-up... today I replaced the PCM with a used one I found online. No more CEL.