OK, here's the situation. My wife and I bought a really nice condition (and I mean nice) 240 DL wagon with the B230F "Red Block" engine. Runs like a top and then engine has some serous snot (it will peal out if you give it good throttle). Looses no oil, oil clean even after six months and three thousand miles (and it has 220K miles on the engine). Probably needs a new set of hushers on the valve stems when I do a tune up (and maybe a shim or two). No piston slap (which is common for this engine from what I understand), but a somewhat noisy valve train (hence, hushers need to be replaced) and noisy injectors (which, I understand is fairly normal). Gets about 25 miles per gallon combined "city"/highway and nearly 30 on the highway.

Here's the strange part (and the previous owner noted this) - the check engine light is on. If you pull the codes and do the diagnostics for the ECU (that built in LED and port system) you come up with the following codes:

113 (O2 sensor or wiring for O2 sensor, etc.,)

231 - (Screwed up fuel mixture).

Considering how well the car runs, I decided to delve into the other diagnostics. So, I ran through the whole routine and found that the ECU shows that the Throttle Position Sensor is not functioning, and that is the only problem other than the 113 and 231 errors.

So, to double check, I zeroed out all the codes and drove around for a while. The check engine light did not come on while driving. It did, however, come back on only after the car cooled down and was restarted. As long as the engine remains relatively near operating temperature, the check engine light (and hence the error codes) do not come on/set. If you let the engine cool down a while (about two hours), the check engine light comes on and stays on when you restart it.

Would I be right in presuming the O2 sensor (or its wiring) and the Throttle Position Sensor are toast and should be replaced and go from there - or - should I leave well enough alone?

As a side note - this engine has no air pump/air injection system/pulse air on it, nor does it have any evidence of any such system (which I would suppose was required of that vintage in the US? - previous owner bought it used).