1999 Cadillac Eldorado that shakes when pressing accelerator pedal going up hill.

Sounds like secondary misfire. Is 14000 miles correct, or 140000? In either case, I would remove the plugs and check the ceramic insulators for sign of carbon tracking. In the event there is carbon tracking on one or another, replace that(or those) plug(s) and wire(s). Check also the coil terminals where the plug wires attach, for signs of corrosion and replace where applicable.