Fuel Pump or PCM?
 

I have a 2004 taurus 24V 3.0 with 140,000 miles that started to run very rough and then stopped running on the freeway the other day. Had to get it towed. I noticed that the gas gauge read empty when the tank was full. That issue has since corrected itself, and there is fuel pressure within tolerance. Plugs were fouled, but were replaced, but car will still not run. Problem is that the PCM is not giving any good codes to help. Not exactly sure what the problem is: Fuel pump, PCM or other (like connection)?

What were the plugs fouled with?

Gas, to the best of my knowledge. They were black. The mechanic wanted to rule out the plugs so they replaced them.

Since you have someone working on the vehicle they may be following a path of troubleshooting where they are observing different things and not necessarily telling you everything they see. So for us to say what is causing the problem could be only partially correct since we don't know all the mechanic is seeing.
Did whoever was driving the vehicle just purchase gas shortly before the problem appeared? Were the spark plugs wet when removed ? The plugs being black as described and wet could indicate a loss of spark, or spark timing not being correct. A lot of mechanics/ techs can't handle suggestions from other people so, it might be best to let him/her follow their own path and see if they can find/correct the problem.
If your mechanic gets stumped and we all get there sooner or later,that might be the time to make the suggestions. How do you feel about that ?

The mechanic has checked fuel pressure, fuel flow, contamination, the Fuel Driver module, all tests came back negative. All items are pointing toward the PCM which has been removed and is being tested.

Please , if you can, let us know how the PCM was tested aside from substitution with a known good unit.
Just because I don't know of a tester to check the PCM outside of the vehicle , doesn't mean one doesn't exist. Usually the only places that have that equip are electronic repair places. We learn something ever day.

It is recommended to clean the Plug-in's after some time as there is present some sort of carbon on it. Specially in the cold countries, this thing matter's a lot. So if you tune it on regular bases, then there is vary little chance of happening like this.