Cadillac Repair: 1989 cadillac eldorado shutter when accelerating uphill, shifting into overdrive, cadillac eldorado

Question
The engine is shifting into overdrive at 43 mpg and feels bogged down and
begins to shutter hard(like stalling a manual transmission) when trying to
accelerate uphill. Service engine light comes on occasionally but turns off
when the ignition is turned off. Any clue what this could be?

Answer
Perform this test procedure:

1. Turn ignition switch to the ON position only. Do NOT start the engine.

2. On the climate control panel simultaneously push and hold the OFF and WARMER (^) buttons and hold them in for 3 seconds and then release them.

Tell me EVERYTHING that displays as if you were video taping the fuel data display panel.

Turn ignition OFF.