My apologies for a lengthy post here.

Our 1990 245 has covered 211k miles and is now serving a third generation family member.

Three weeks ago it developed a rough running condition along with a massive appetite for fuel. Since it was due, I changed the fuel filter and discovered at that time that the in tank fuel pump was dead (the main pump sounds like it is running). Replacing these two items did not change either condition.

With the mileage on the car I went ahead and replaced both the speed sensor and the ECU temp sensor. I didn't expect these new parts to make any difference really just thinking that they will hopefully be good for the next 200k miles.

We also replaced the plugs, rotor cap and button. Again, didn't think it would improve anything, but it was time to do these things anyway and it certainly wouldn't hurt.

The throttle position switch was checked and confirmed to be dead. We replaced it and again, there was no expecatation that this would make anything better as our research indicated that this switch has no bearing on mixture control.

While in the neighborhood, we removed the throttle body and cleaned it and its ports. Flame trap service was just done 3 months ago.

According to the values read on the VOM, the Air Mass Meter is good. Cleaned it with the correct cleaner re-installed it and no difference in running condition.

We checked the O2 sensor with a VOM and the resulting values incidated that it was dead. The O2 sensor was replaced and interestingly, the car ran very strong under load, suprisingly strong. However, it still runs roughly and is pumping out black puffs of un burned fuel.

Incidentally, all fuel injectors appear to be working - VOM confirmed they all have voltage. Using a mechanic's stethoscope each injector is clearly firing.

We did the quick check for a faulty fuel pressure regulator - no raw fuel smell on the vacum side of the diaphragm.

I mentioned above that the car is burning a tremendous amount of fuel. I have gone through a full tank of fuel in 100 miles while going back and forth to a friend's house during this diagnostic marathon.

At present, on board diagnostics is throwing two codes:

221 - Fuel system compensating for extremely rich or extremely lean air/fuel mixture at cruise. That is if the "Check engine light" is on.

231 - Fuel system compensating for extremely rich or extremely lean air/fuel mixture at cruise. That is if the "Check engine light" is off.

The 231 code would appear to me to be relevant to my car as my check engine light is off.

I have not checked fuel pressure at the rail. And have not checked the ECU. I seem to have read that while some AMM will check out as good with a VOM that they can still be functionally dead.

Again, sorry for the lengthy post, but does anyone have any thoughts on next steps.

Thanks again for the great resource.