1991 Lincoln, Multiple problems, related?

1991 Lincoln, Executive Series, front-wheel drive, 3.8 V-6, 138,000 miles
Several questions...
1) Intermittent "CO" message in the fuel guage area. What possible
malfunction(s) does this refer to?
2) Oil pressure readout goes low, intermittent. Returns to "normal" after a period of time which varies. Bad sensor, wire or ground?
3) Motor runs fine with no load, in "park" and "neutral", and on dyno in drive, accelerates through entire range with no problems, but seems to misfire during actual road use under light to moderate acceleration. Depending on speed when this occurs, the misfire or skip can range from a single miss to multiple occurences which feel like the shudder of very out-of-balance tires (at highway speeds). Motor smooths out immediately if accelerator is released. This occurs even if overdrive is locked out. Oil pressure goes low, but I should think that this is to be expected and unrelated to #2.
Recent work: Car was parked for about 18 months, after A/C compressor seized. Was driven approx. 3 miles with no serpentine belt. Shortly before that, distributor was replaced during "routine" tune-up when cap screw snapped off in housing and attempts to drill and tap destroyed the "ear".
Since resuming use of the car, both fron axles were replaced (CV joints bad), ball joints and control arms replaced (worn), A/C compressor, serp belt and battery replaced. (I don't think any of these are related, included for completeness.)
I'm not a complete moron when it comes to cars, but the majority of my experience comes from before computerized motor control and fuel injection. (Give me a 1970 AMC Ambassador with a 360 4bbl and an unlimited supply of gasoline and it would never see a profesional mechanic...damn, I miss that car.)
Thanks for your consideration.
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injectors]
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Plugs and wires are new and timing was checked and good. I've been leaning towards the fuel injection as being off, but it seems odd to me that the symptoms would not be present under all conditions, especially on the dyno. I did run injector cleaner through it, but I don't put much faith in canned repairs.

Blew a lower radiator hose on a hot Saturday night about 10 miles outside the city limits of Killeen, TX (Back before it got built up like it is now) on the way to the dirt track. By the time I walked back to town the parts store was closed and didn't open until Monday. When I got the hose and walked back out there the car was gone. THP had towed it and it was "in storage" for more than a week by the time I found out what had happened to it- the storage charges were more than I could afford to pay and I never got it back.
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Arthur Dent wrote:

CO = Circuit Open. A bad ground or fuel sender can cause this, as can the fuel float's rheostat going past its normal range.
Oil pressure varying can be any of the three named, as well as a bad gauge. It could also be actually happening; stick a mechanical gauge in the oil sender port to check it.
For misfire & rough running, could need tune-up (plugs, wires, etc.), vacuum leak, or maybe IAC or EGR valve.
INVEST in a $35 digital code reader and pull codes to help pinpoint the problem(s).
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Ah, thanks, the owners manual mentioned it but didn't explain what it meant, and my Chilton's manual didn't mention it at all.

Good idea.

Plugs and wires were replaced just before the compressor seized. Vacuum leak sounds like a good possibility, as a family of squirrels was living in there before I bought it, and chewed some other stuff, maybe they got a vacuum line too.
Would it pull more vacuum under load than when parked or on the dyno?

Will do. I was going to buy one a couple of years ago but didn't.
Thanks much.
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