What is wrong with your 1998 Plymouth Neon if it chugs when you start it and the check engine light just keeps flashing and not giving a code?

I would have your computer recalibrated and find the source of why it got messed up in the first place. Also a slipped timing belt and bad head gasket will also cause that very same problem. I race these little cars so i have a pretty good idea what would cause allot of problems with them. If the check engine light stays off during normal driving i would definatly look into the engine timing and or head gaskets.