My 97 grand Marquis will not start all of a sudden, after putting it in neutral and pushing it side to side it starts for a whole day, then the following day it won't

This is normal.

Best answer!

gas is only good for 30-60 days drain the old fuel out and put in fresh gas

Check/replace the brake light switch on the top of the brake pedal.

the transmission is gone

Very likely you have a loose connection on your transmission shift linkage, or you have a shift cable that is no longer tight.

First jack up the vehicle and secure with a jack stand. Check the connection on the drivers side of the transmission to make sure it is connected tight. There should be a nut holding the shift lever in place. If it is correctly fastened, remove the steering column plastic covers by unscrewing screws and check for loose connections.

for a quick fix, try putting the car in neutral, put the key in and start the car. you'll have to have the problem checked out. the shift lock solenoid circuit is faulty.

do the rpms rev? if not than its not the trans it could be fuel related or clogged cat

change the idle air control valve.

a simple test here may reveal the fault
put the hand brake on and in neutral
start the engine
if it idles ok then put your foot on the brake
if there are problems then have the brake booster replaced
that is indicated because at lights , you have you foot on the brake
when turning people use the foot on the brake to maintain control