Curious about the O2 sensor. That's a definite possibility, or at least a contributing factor for poor acceleration. I didn't suspect this as Phil didn't mention a Check Engine light, which should have been set by the 2-1-2 Missing/faulty O2 signal DTC. Fuse 4 is the O2 sensor heater and won't by itself trigger a code, but could in theory indirectly trigger the code if the ECU was bright enough to sense that the O2 sensor was taking to long to warm up, either from no heater circuit or a badly fouled sensor.

I would:
a) Make sure the fault wasn't transient and is still present by doing an OBD reset and making sure the code returns within the next few starts.
b) Inspect the O2 sensor wiring under the car to make sure the cable isn't damaged, paying special attention to where it goes into the sensor and as well the firewall clips.
c) Open the O2 sensor connector on the firewall and make sure there is some kind of continuity on the heater circuit between pin 2(black wire) and pin 3 (yellow-red).
d) After a good warmup and with the engine running, open the O2 sensor connector on the firewall (or probe into the back of the pin) and measure voltage between pin 1 (green wire) and chassis ground (the black wire system ground point on the fuel rail is best). For a working O2 sensor, the voltage should be between about 0.1V and 0.9V and will fluctuate depending on current engine rich/lean running conditions, typically responding within a second or so to between 0.4V and 0.8V going to/from idle to sustained higher revs (like over 2,000 rpm).
e) Failing the above, plan to replace the O2 sensor.

The 1990 240 wiring diagram schematics can be found on this Google drive collection
https://drive.google.com/drive/u/0/folders/1CuClHEuSSHxeUOxnDhmA7FEozZPJPJN2

The closest online green manual I know of for a later 240 with LH 2.4 is the final year 1993 one in the OzVolvo technical archives
https://ozvolvo.org/archive/?download=VGFsaWVzc2luIFBlbmZvdW5kIC0gVFAzMjM1Mi0xIDE5OTMgMjQwIFdpcmluZyBEaWFncmFtcy5wZGY=

Bill, please pass the message on to Phil in case he can't see this, which may be due to the recent excessively slow response of the brickboard server. Oddly, I find the server much more responsive in morning hours, making me think Jarrod's own server gets busy doing other things during the rest of the day.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now