2003 Dodge Neon

https://www.2carpros.com/articles/service-engine-soon-or-check-engine-light-on-or-flashing

Have the computer scanned for code/s-you have a problem within the engine management system that caused the CEL to turn on-This is your starting point of diagnosis,finding out what's going on

code is P0440

That code is not causing the check engine light to flash. There has to be other codes in there.

Shaking the booty and nasty smell for away from the Evap System-here's what P0440 means-Like Wrench said it has to be something else that the brain is sensing with its parameters/actuators-rescan it a few times and erase it and see what happens

A code P0440 could mean one or more of the following has happened:

•The gas cap is not installed or working properly
•The purge solenoid has failed
•The canister is plugged and not working properly
Possible Solutions With a P0440 OBD-II trouble code, diagnosis can be tricky at times. Here are some things to try:

•Remove and reinstall the gas cap, clear the code, and drive for a day and see if the codes come back.
•Inspect the EVAP system for cuts/holes in tubes/hoses
•Inspect for damaged or disconnected hoses around the Evap purge solenoid
•Check and/or replace the sensor
•Check and/or replace the purge valve
•Have a professional use a smoke machine to detect leaks

the light only flashed 1 out of the 4 times we turned the car on, when that happened the car was shaking really bad and i smelled and odor like rotten eggs, now the car doesn't shake anymore but the engine light in ON not flashing anymore.

Scan it again and let us know if its a P0420 which involves the snitcher and the scrubber in other words the oxygen sensor/s and the catalytic converter