2003 Dodge Neon Rattle

Hello jclint77084, welcome to 2carpros.

Before we think of the obvious such as engine or transmission noise, lets start with the exhaust problem.
Exhaust rattles and/or vibrations may also be transmitted through the chassis and feel like something else. To rule out this possibility, inspect the exhaust with the engine running and the vehicle on a lift.
To also rule out a broken motor mount, check for signs of physical contact (scuff marks, shiny spots, etc.) between the engine, transaxle or exhaust system and the rest of the vehicle. Prying up on the engine and transaxle can check the integrity of the motor mounts.
check oil when engine is hot if the level is good, check the oil pressure .Worn, leaky or dirty lifters can also cause valvetrain noise. If oil delivery is restricted to the lifters (plugged oil galley or low oil pressure), the lifters won't "pump up" to take up the normal slack in the valvetrain at idle. A "collapsed" lifter will then allow excessive valve lash and noise.