check the distributor. bearings could be going bad and throwing dust onto the optic sensor, causing a misread. spray it off with sensor cleaner ( be sure to spray under the optic sensor ). let it flash off for a minute, put everything back together. works for me.
take off throttle body and clean it with throttle body cleaner.
Clean the carbeurator and lube the throttle cable.
On a 1996 you will have OBD2 which means a repair shop can hook up a scanner and read codes and tell you exactly what is wrong. That will eliminate the GUESSING and save you money by not installing parts you DO NOT NEED.
could be a vacuum leak, or throttle positioning sensor
About a million and one different things can make that happen.
I have a 2003 mercury grand marquis will sputter around running 35 - 60 mph ?
I don't think your asking the Q right it must be the engine doing it, maybe egr
Sounds like a vaccum leak
sounds like you need a new accelarator pump in your carburettor
Look for a hole in the PCV valve hose on the backside of the engine.
I would check the ignition timing and set it to the desired specifications. Next I would clean the throttle plate.
It's lean. Check for vacuum leaks, and make sure the fuel supply is functioning properly.