2005 neon with 35000 miles on it is now showing p0304 code and makes a churp noise when started already changed the belts also idles rough at red light noticed idle drops to 500 gets roug?

* A bad spark plug

* A bad spark plug wire

* A bad ignition coil

* A vacuum leak

* A fuel injector problem

The chirping noise could be caused by a number of things, including:

* A bad belt

* A bad pulley

* A bad water pump

* A bad alternator

The rough idle could be caused by a number of things, including:

* A dirty throttle body

* A bad idle air control valve

* A vacuum leak

* A fuel injector problem

I would recommend taking your car to a mechanic to have it diagnosed. They will be able to determine the exact cause of the problems and recommend the best course of action.