How do you remove the gear shift knob on a 94 eldorado

Screw it off

If you have a stick shift ( floor shift) remove the boot around the gear stick and the insulation on the floor to reveal the 4 bolts that hold the shift turret on to the top of the box. Undo the bolts and lift the gear lever assembly out of the gear box.

knobs screw on normally and there is a small locking nut underneath the knob . IT could look like a taper ring to finish off the knob but it should turn down the lever to release the knob.

Had same problem on my 94 eldorado touring and it turned out I had bad ign coil. This sets a 41 code. Check codes for no cam ref signal. Sounds stupid but if one coil stops firing on only one cyl it sets that code. There are 4 coils and they run 2 of one end of ign module and two of other end.

it seems like your shift fork is in between gears you must remove the shift tower and align all the shift levers then drop the shift knob into the middle being neutral tighten it up and it should be ok but remember the replacement could be slightly thinner then the original and causing this new problem.

I'd check & lube all kickdown cables in the area of the throttle body, as well as follow any to transmission and lubricate well there too. It almost sounds like something may be seized and holding into lower gear.

There is a plastic actuator stick under the shift knob. Remove the "horse shoe" clip from the shift knob and remove knob by pulling strait up. You can twist it right and left a very small amount to loosen the knob, but not much.
Once you have the shift knob removed you will see the plastic actuator stick. Push down on the stick and put shift lever in park. If that works, the shift knob or stick is worn out.
Let me know.
Regard,

On my 2000 jetta glx, I had to replace both the shift knob and boot as one. It is built as one unit. You have to pull the boot up over the shift knob, break/bend a clip to "unlock" the shift knob then pull up. I hope the new knob you got has the boot built in and comes with a new clip.